Universal wavefunction

The topological conference was partly dedicated to Raoul Bott who passed away last month. Hirosi Ooguri spoke about chiral baby Universes, Greg Moore about torsion, and so forth.

Robbert Dijkgraaf was the last speaker - and he had the opportunity to discuss topics that are closer to the dreams of physics. First, he helped the mathematical portion of the audience and defined a physicist as a supersymmetric hero (also known as a superhero) who can save the Universe. ;-)

After the beginning, he was explaining things that I find completely uncontroversial. If you fully compactify all spatial dimensions of string theory (compactification on "M9 x R" where "R" is time), you obtain cosmology where everything is connected and all transitions may occur as long as you have a finite energy.

Robbert believes that the right Hilbert space for this completely compactified string theory is a symmetric product of another space "H" - which corresponds to the fact that you may have disconnected Universes. This symmetric product may also be rewritten as a sum over superselection sectors labeled by different fluxes and charges.

He continued with explanations of OSV and OVV - the Hartle-Hawking stuff. OVV is based on an analogy of the cylinder diagrams in string theory that can be interpreted in the open string channel or the closed string channel. The path integrals compute a sort of index that only depends on a few parameters. A conclusion that Dijkgraaf offered is that the index counts various things like the ground states of some quantum mechanical models whose presence prefers a certain kind of Calabi-Yau manifolds with symmetries.

Robbert's ultimate goal was nothing smaller than to reveal the grand structure that underlies all of string theory - i.e. also all of mathematics and physics. A part of this task is to understand the overall space of all Calabi-Yau manifolds. Robbert promoted the program of Miles Reid: every Calabi-Yau's can be obtained by gluing "J" copies of an "S3 x S3" via conifold-like transitions. This procedure should be analogous to the way how you obtain genus "g" manifolds by gluing tori. The simpler manifolds appear as degenerations at the boundary of the moduli space of the really complicated manifolds. Dijkgraaf discussed how this can be reconciled with the picture of a Calabi-Yau manifold as a T3-fiber over a three-sphere. The fiber is degenerate on special points of the base that look like a graph (imagine a skeleton of a tetrahedron).

As soon as the discussion started, Michael Atiyah proposed that Reid's program can be combined with the observations of Atiyah-Witten that the cone over "S3 x S3" is a manifold of G2-holonomy which would allow one to acquire a more unified seven-dimensional perspective on this whole geometric problem.

At any rate, the point of Robbert's talk was that many people should try to study the properties of the Hartle-Hawking wavefunction in string theory.

Concerning this general problem, I started to believe that the small volumes of the moduli spaces of complicated Calabi-Yau manifolds mean something. For example, consider the quintic. The volume of its complex structure moduli space is a number that has some large positive factors in the numerator - but they are beaten by a gigantic number of order "120 factorial" in the denominator.

The volume is tiny. You should not be too impressed by this tiny number because all moduli spaces with dimensions of order 100 tend to have such tiny volumes. However, I feel that the natural Hartle-Hawking measure on such moduli spaces will be more or less uniform, and therefore the probability will be roughly proportional to the volume. If this is true, it means that the backgrounds with a large number of massless (or light) fields will be heavily suppressed and the Hartle-Hawking picture will prefer configurations with a minimal number of light fields (I am thinking about the scalar fields right now).

The relative weights of Calabi-Yau manifolds with different dimensions of their moduli space should be determinable by a proper analysis of the region near the critical transition that connects them, I think.

No one yet knows how to do these calculations right and quantitatively, but I definitely share the belief that people should try to look at these questions and understand the behavior of all relevant factors while avoiding prejudices about the philosophical conclusions.

NP-hard landscape problems

The topological conference has attracted a lot of great mathematical physicists and mathematicians. I will report on Robbert Dijkgraaf's talk in a moment.

Frederik Denef who is one of the young big shots in the topological landscape interface allowed me to inform you that he and Michael Douglas are completing two papers about the NP-difficulties of locating the right vacua in the landscape.

If I understand well, "N" denotes the number of different fluxes, and they can rigorously prove that you need a longer-than-polynomial time in "N" to go through all the configurations of different fluxes in order to identify one with plausible values of quantities such as the vacuum energy.

You know that it is hard to prove that some apparently difficult problems are NP (non-polynomial), which is the source of the open questions about the so-called NP-completeness, so I am curious how the proof roughly looks like.

The philosophical conclusion is obvious: you should not even try to find the right vacuum because the required time will exceed the recurrence time of the Universe. Peter Woit and his gang will probably have some new exciting material to talk about. ;-) You may guess that my conclusion is that if the NP-hardness is true, then the class of the vacua is likely to be physically irrelevant.

In another paper, they study cosmological consequences of the fact that Nature cannot "compute" these things in a polynomial time either. Expect that the text above contains certain inaccuracies because there were no formulae written down in the discussion.

Terminological correction by Andy Neitzke:

I think NP is not "non-polynomial" but rather "nondeterministic-polynomial" -- a problem in NP is one which can be solved in polynomial time by a computer which is allowed to branch nondeterministically. So every problem in P is in NP. A problem is called NP-complete if it is in NP and if furthermore every problem in NP can be reduced to it in polynomial time. From that description it might sound amazing that there are any NP-complete problems, but there are -- and there are some "standard" tricks for proving that a given problem is NP-complete. The deep open question which nobody knows how to solve is whether NP = P, i.e. whether all NP problems can actually be solved in polynomial time even by a deterministic computer.

If I remember right, "X is NP-hard" means that every problem in NP can be reduced to X in polynomial time, but X itself might not be in NP.

Joachim Martillo's e-mails

Joachim Martillo whose e-mail is ThorsProvoni@aol.com has been one of the major external sources of tension during the so-called Summers controversy in 2005. The subtlety is that Martillo promotes anti-semitic opinions. For example, today, many people received his e-mail "Summers' latest outrage". What is the outrage? It is the largest

• Shabbat dinner

that is planned for February 10 and will become the largest Shabbat dinner that ever took place at Harvard. Why is Mr. Martillo so offended by the dinner? It is because he believes that the Hillel Society is a racist organization that moreover promotes zionism - namely the idea that the state of Israel has the right to exist (which Mr. Martillo obviously considers to be a heresy). The Wikipedia page above makes it clear that Hillel is the Foundation for Jewish Campus Life. It's the most correct Jewish campus organization you can get.

Mr. Martillo also claims that some distinguished professors at Harvard add an anti-Slavic racist aspect to the activities of Hillel. As a Slavic person, I declare that the contacts we had with the people whom Mr. Martillo accuses of racism have shown no evidence supporting it. In other words, as a member of a hypothetically discriminated group, I must say that according to all evidence I have, Mr. Martillo is not saying the truth to us.

Alito: 58 vs. 42

Four democrats supported Samuel Alito and one Republican opposed him. Congratulations to the 110th justice.

Quantum field theory textbooks

This article, originally called "QFT didactics", is a list of some quantum field theory textbooks.

Peskin and Schroeder. This textbook has become the new mainstream standard and replaced many older books such as Bjorken-Drell.



Weinberg's three volumes. Steven Weinberg who needs no introduction wrote a more detailed set of three volumes with some interesting yet reliable things that go well beyond the mainstream material. The three volumes are Foundations, Modern Applications, and Supersymmetry.

Mark Srednicki. The textbook of the physicist who is also the chair of physics at UCSB has been available online and it has been praised by many readers. It's time for you to buy the real version.



Anthony Zee. Anthony Zee is Mark Srednicki's colleague from UCSB. His book is really cute, has a funny cover, and offers some intuitive physical concepts that are not explained elsewhere, much like some cute stories from the history of physics.



Tom Banks (2008). I recommend you a new book on quantum field theory by my (former) adviser, Tom Banks. There's a lot of wisdom that I have learned from, too. Many things are presented in a similar way as I would do so, and others are done differently. A nice summary of LSZ formalism, gauge invariance and its roles, the fate of different types of symmetries, phases of gauge theories, renormalization and the logic of effective field theory, instantons, and monopoles, among other things.



Lowell Brown. Lowell Brown's book has been praised because of its pedagogical value but be ready that its scope is limited. The author chooses a perspective in which quantum field theory is just another level of computing mechanics and quantum mechanics. That's why things like non-Abelian gauge theories are completely missing.



Renormalization methods: a guide for beginners, by W.D. McComb. It is a fun book that can explain renormalization even to undergraduates, as many reviewers argued. Renormalization is normally associated with quantum field theory - and the text covers some of it - but it first appeared in classical physics. Many examples are very intuitive and accessible.



Michio Kaku: Quantum field theory, a modern introduction. Covers quite a lot, from motivation, Noether theorems, type of scattering, gauge theories etc. to BRST quantization (only two pages), string theory, supersymmetry, and quantum gravity. Sometimes the presentation may be too short but it is helpful as reference and there are other advantages. Includes extensive problem sets.



Eberhard Zeidler. I haven't read it but among other things, this book has a very detailed coverage of history, the role of Göttingen, a presentation of heuristic methods etc. Quite original!



This list is far from complete but if someone is looking for a textbook, it could be useful. See a similar list of string theory textbooks.

Many of the readers have strong opinions - and they may want to share their ideas what they think is most important for teaching QFT. In what direction would you push the classes? What do you think is missing in the mainstream courses and/or textbooks?

Topological conference

The event's website contains basic data about the conference. Let me exceptionally behave as a linker-not-thinker.

Cloture passed

As we predicted on Thursday, the proposed filibuster has been defeated. The numbers were 72-25 in favor of cloture: only twenty-five Democrats joined the unrealistic and hopelessly negativistic bandwagon pushed by radical activists at dailykos.com and elsewhere. Alito is going to be confirmed tomorrow.

The main "kos" from dailykos.com celebrates the fact that despite the vote that they have lost, they were able to send a huge number of obnoxious e-mails and organize lots of telephone calls and threaten, terrorize, and annoy virtually every Democratic as well as Republican lawmaker and everyone else who matters. The main "kos" believes that this fact is great. On the other hand, your humble correspondent thinks that these people should be deeply ashamed for their behavior.

Such an approach resembles asymmetric wars - typical strategies that are followed by the terrorists and others - but it is not a good attitude to influence events in a democratic system because the amount of terror that the Democratic lawmakers had to face will definitely be counted as a huge minus for the Democratic Party in the 2006 elections.

By the way, it is not just dailykos.com that is producing tons of hatred and insane threats. PZ Myers has listed all the reasonable Democratic lawmakers and associated them with various disgusting animals. Others plan to write additional nasty letters. They think that they have the right to be furious and "hold them accountable". Others are already buying rifles and cheap ammunition. Hundreds of other reactions are here.

Radical leftwingers are dangerous; they have always been dangerous. Incidentally, dailykos.com must have a special black list of hosts and domains. When I try to open dailykos.com from the Harvard computers, I get a "404 Not Found" error. ;-) Of course, I can open it in hundreds of other ways...

Atchoo theory

V. Gates, M. Roachcock, E. Kangaroo, and W.C. Gall from the Institute for Really Advanced Study (IRAS) established a new

• Official Blog of String Theory

and tried to explain the new Atchoo theory. :-) Thanks to Count Iblis for the tip. Don't forget that the links on the Official Blog of String Theory actually work. Enjoy.

Warren is also making fun of animations on technically advanced webpages as well as of wasting time with unpublishable nonsense. ;-)

Yukawa couplings in the heterotic MSSM

Start with the unique known heterotic background whose visible spectrum matches the pure MSSM - namely the heterotic MSSM. What are the Yukawa couplings and the fermion masses? Braun, He, and Ovrut compute the answer (in the zeroth approximation) tonight:

• hep-th/0601204

The resulting textures, affected by the selection rules implied by the Calabi-Yau geometry, make one generation of quarks and leptons naturally light. The word "light" means that the cubic terms contribute zero and the actual masses of the light family arise from higher-order and non-perturbative effects. That means that the cubic approximation is not enough for you to compute the mass of the electron.

The nonzero Yukawa couplings connect the "generation 1" with "generation 2", or "generation 1" with "generation 3", using the appropriate Higgs in each case (which is different for up and down quarks and/or leptons). The "generation i" are just some basis states, not the mass eigenstates. You can see that there are 8 couplings that are complex a priori. With two massive generations, you can assume, without a loss of generality, that the couplings are real. If you don't calculate the numerical value of the couplings, you will have no prediction for the quark and lepton masses: there are 4 quarks and 4 leptons in the two heavier generations, precisely parameterized by the 8 Yukawa couplings.

On the other hand, you may follow and surpass the authors and try to analyze the Yukawa couplings expressed as the integrals in the equation 22. If you're lucky enough, you could predict a non-trivial relation between the masses of the two heavier fermionic families. (The large masses of the right-handed neutrinos will, however, complicate the analysis in the neutrino sector.) The reason why it is complicated is that it is expected that with the non-trivial bundles turned on, the Yukawa couplings won't be simple integer-valued intersection numbers that are constant over the moduli space. Instead, they will be general functions of the moduli. The values of the stabilized moduli are therefore needed to predict the quark and lepton masses.

If you analyze what one can predict without much bigger effort than the already difficult calculation of Braun, He, and Ovrut that may be comprehensible roughly to 12 people in the world, it seems that one can exactly predict the lightness of a single generation relatively to the other two - which seems to be a correct prediction or more precisely a postdiction.

Funniest personal joke ever

Wolfgang has found the funniest personal joke ever. (Politically incorrect adjectives have been replaced by their more acceptable counterparts.) Click at the link on his blog - it is straightforward to get to the joke. This joke is, among other things, a realistic testimony about the number of original thinkers and original ideas born in the blogosphere. :-) In this sense, this short text is an appendix to the previous article attempting to prove a point.

Influence of blogs and antiblogs

As many of you have already figured out, this website is not a blog. It is an antiblog. It was established as an antiblog, it has always been an antiblog, it is an antiblog, and it is going to be an antiblog in the near future. What's the difference between a blog and an antiblog? The answer will become obvious if we sketch what is the direction in which most blogs are trying to push the public opinion on a whole variety of issues.

Let us start with the following observations. Our society relies on a certain hierarchy of skills and roles. Even though most of the U.S. citizens may believe creationism, this fact does not prevent the biology departments of universities and other institutes from pursuing the correct science about species based on Darwin's precious insights.

How is it possible? Why have not the creationists taken over biology yet? Why do the university physicists "believe" in relativity despite the opposite belief of the general public? Why hasn't the rational approach to hundreds of other questions been eliminated from the "establishment" yet? Well, it is mostly due to the hierarchical nature of the pyramid of knowledge. The hierarchy in the previous sentence refers both to the structure of the actual scientific insights as well as the sociological structure of the scientific community.

When you're accepted into the college, you simultaneously do two things: you increase the probability that you will influence certain questions that depend on the intellect and other skills and that require a certain effort. However, you also increase the probability that you have the right opinions about and the right approach to the very same questions. The obvious reason behind both changes is that the college students are likely to be smarter than average people without a college. Such a selection mechanism takes places at many other levels in Academia as well as politics. One of the results is that most crackpots or conspiratory theorists can't really become professors or opinionmakers.

I am not advocating elitism as a tool for some people to dictate others how their life should look like; I am only describing the healthy dynamics that assigns different roles to different people.

The blogosphere circumvents this equilibrium that has been built and refined for a long time. What determines whether a typical blog is going to be successful is something rather different from the mechanisms that act within the pyramid of knowledge. What matters is whether you can express the opinion of a large number of people in an attractive and provocative way.

The extreme example is Daily Kos. The success of this website relies on the existence of tens of millions of rather narrow-minded Bush-bashers who are the potential readers and "contributors" to that website. They are convinced that the more radical you are, the better or smarter human you become. They completely avoid all the tests and confrontations that would normally occur before someone would become influential in politics or in Academia. There are thousands of them - and this very large number itself is very intimidating and some people are even afraid to say that most of the members of the Daily Kos community are what they are, namely irrelevant fanatical bigots.

Today, Jim VandeHei explained in the Washington Post how this new force based on the Web influences the Democratic Party. Exactly when the Democrats are trying to regain a moderate human face, the numerous radical left-wing bloggers are trying to push the Democratic Party to the left and "order" the Democratic lawmakers to do a whole plethora of really dumb things such as the filibuster attempt against Alito: an act of obstructionism that is doomed from the very beginning and that moreover shows that the Left does not want to tolerate any people (or even judges) who disagree with their liberal politics.

The radical "base" of bloggers can provide the Democratic Party with excitement, infrastructure, and even financial resources (moveon.org donations and/or DailyKos campaigns). However, at the very same time, the Democratic Party knows that the influence of this "base" must be regulated because once the Democratic Party becomes a hostage of this "base", it will be unelectable because the radicals are literally appalling for 3/4 of the population or so. Kerry has joined Dean in relying on the extreme base while Ms. Rodham remains in a similar state as Schrödinger's Cat.

Some of the dynamics is inevitable. The bloggers simply are less special people in average. The intelligence and the knowledge of an average blogger is almost certainly below the intelligence of the people who "mattered" before the word "blog" became popular. On the other hand, the bloggers like to fight much more than the average people in the society - and there are obvious microscopic explanations why it is so: this is the reason why many of them started their blog. (Arguably, the last sentence may hold for some antibloggers, too.) Try to guess where does this combination try to push politics.

Similar comments can be said about science. Many bloggers and especially blog commenters expose attitudes towards science that are exactly equivalent to the attitudes that would prevent them from climbing the "pyramid of knowledge". Some bloggers promote their Intelligent Design; other bloggers promote their ideas that science (or theoretical physics) is another religion. They often do not have any other idea than these two or several other widespread intellectually limited paradigms, and they're not willing to study any "details" because the basic "paradigm" is always more important for them. Some of the blogs even have names that make it obvious that the whole blog is and always will be exclusively dedicated to one silly idea. Just think about the blogs you know and try to figure out how many of them focus on one "point of view" only: the percentage will be very high.

It should not be surprising that some bloggers whose ability to think about science is stuck at some level that would prevent them from being accepted as PhD students get a significant amount of support from other people who are equally stuck. In physics, what you need to learn has many layers, and thousands or millions of people are stuck at virtually every level where they can get stuck.

It should not be surprising that there are thousands if not millions of crackpots around. In the case of physics as well as other disciplines, they get stuck with some particular misconceptions and can't make the next step. They seem to be unable to understand that it is exactly this inability of theirs that would prevent them to climb the traditional pyramid of knowledge.

In the blogosphere, however, the rules of the game are different. You can sell your breathtaking stupidity as an interesting alternative viewpoint on politics, science, or physics - as long as you find enough readers who suffer from the same kind of stupidity and as long as you are ready to write down a lot of stuff and post it at various places. It is exactly this stupidity that makes people above them in the "old world's pyramid" to think that these bloggers and blog fans are not worth attention - but whether something is positive or negative can easily be flipped on the blogosphere.

Most scientists don't worry about these new influences. But the influences are there and we should not hide our heads into the sand. Crackpots who attract other crackpots are unfortunately emerging as an independent voice that should be listened to when any topic is discussed. This message is addressed primarily to all journalists from the "old world". Be very careful if someone tries to pretend that he or she has very relevant opinions about any question just because of her or his blog who is read by a few thousands of people. This is no test of scientific value, and in the case of politics, it is no test of political plausibility of their viewpoints. Most of the readers will be average people who have no idea about the actual issue, and the fact that they happened to be attracted to a particular blog is inconsequential.

If I summarize: most blogs push a one-dimensional, intellectually limited point of view that is popular among average people (or below) but less popular among those who have climbed the pyramid. Also, most blogs are attempting to flatter a particular group of readers and use these readers as a justification to drag science and politics down, instead of trying to educate the readers (and the blogger herself). We have mentioned several other points that should make it clear why The Reference Frame is an antiblog.

20 years after Challenger

It has been twenty years since the Challenger disaster. At that time, our teachers would tell us how much the Americans were ahead of the Soviet bloc because of the space shuttle.

Czechoslovakia became the 3rd country in the world whose citizen visited outer space flight back in 1977. Today, Vladimír Remek is a deputy of the European Parliament for the Communist Party. The first name Vladimír is after Mr. Lenin while his surname Remek stands for Rychle-Eeeeee-Mluvící-Eeeeee-Kosmonaut i.e. Quickly-Errrrrr-Speaking-Errrrrr-Astronaut. You can see that Mr. Remek is translated as Mr. Qesea.

Twenty years later, I personally no longer believe that the space shuttle is such an incredible technology. Feynman's conclusions about the space shuttle are here:

• Feynman and space shuttle (O-rings)
• His personal observations

The main point of Feynman's observations is the same as the point of my texts about the Bayesian probability: the probabilities only have a scientific meaning if they can be determined or at least interpreted in a frequentist fashion, and they can only be trusted if the relevant experiments have actually been tried sufficiently many times to give us the result with the desired accuracy.

More concretely, the management's estimates of a mission failure - around 1 in 100,000 of Bayesian probability - were scientifically nonsensical because no one could have determined such a low probability of failure using rational methods, especially because of the top-down approach to the space shuttle design where the individual components can't be tested and evaluated separately.

Today, of course, we know that the probability of space shuttle failure was definitely much closer to 1 in 100 than to 1 in 100,000 and probably even higher. But even without the sad knowledge we have today, the management's Bayesian estimates were always a complete bogus.

Dean Kirby's resignation

Five minutes ago, right after I returned from John Harvard's - where GM has told me many things not only about Ecuador - we received a characteristically nice and diplomatic - and in this particular case also uncharacteristically content-rich - e-mail from the dean of FAS William Kirby announcing that after the spring semester, he will return to his dynamic field, modern and contemporary China, and resign as the dean of Faculty of Arts and Sciences of Harvard University. The whole process looks very elegant - and still, the well-informed readers should be aware that the president has the right to fire the deans independently of the direction of the wind. The readers of The Reference Frame could learn the news even before the readers of The Crimson.

Kerry will lose again

Special welcome for former fans of John Kerry who came from his blog and decided to switch to L.M.

The Reference Frame predicts that our Massachusetts senators' attempt to filibuster Samuel Alito will fail. Filibuster - talking nonsense for many days in order to fight for your own ideology and suppress the will of the majority - is a morally problematic procedure that at least two Democrats will disagree with (update: at least ten).

Moreover, at least two other Democrats are expected to support Samuel Alito actively because they know that the conservatives are better judges in average - and the citizens of their red states know it, too. Conservative judges tend to follow the law - unlike many left-wing judges who tend to write their own laws and include various political correctnesses and similar crap into their "interpretations" of the law.

John Kerry's and Edward Kennedy's inability to realize that their fellow Democrats are not such fanatics as they are shows that they don't really have leading skills. It is a rather un-American approach to go into battles that are pretty much lost from the very beginning.

If you did not know, John Kerry is one of the less well-known far left-wing bloggers (see here) - whose loyal readers call him "Mr President" - and a former presidential candidate. Edward Kennedy is famous for being a brother of the former U.S. president. John Kerry is trying to become visible before the 2008 elections when he apparently wants to get the votes of all supporters of permanent losers and ridiculous puppets.

Wolfgang from ISO42 on the Bahamas forgot to say "Mr. President Kerry, our beloved leader, I will also eat your excrements" and you can see that he simply had to be beaten up by Kerry's gifted fans ;-) as every reactionary straight while male should be. :-)

S-duality and exceptional groups

Anton Kapustin (Caltech) is visiting Harvard. Much like Edward Witten, he is thinking about the Langlands "program" - with a focus that is arguably more physics-oriented (i.e. S-duality-oriented) than the approach of Edward Witten.

Anton has answered many questions I had about S-duality, for example:

When you study the operators that are S-dual to given operators, why aren't you just satisfied with saying that the dual of the Wilson loop is the 't Hooft loop, among other examples?

• Wilson loop is a trace of the holonomy over a representation, and therefore the independent loops are labeled by irreducible representations of the gauge group. The dual label is less transparent for the 't Hooft loop, and similar subtleties need a more detailed treatment.

What is the S-dual theory of 3+1-dimensional maximally supersymmetric Yang-Mills theories with exceptional gauge groups?

• All exceptional groups are self-dual under S-duality, much like U(N) and SO(2N). SU(N) is dual to SU(N) / Z_N while SO(2N+1) is dual to USp(2N).

In "Baryons and AdS-CFT", Witten argued that nonperturbatively, there are two different USp(2N) gauge theories. How is the subtlety reflected in the S-dual description?

• The two USp(2N) theories are actually connected with each other. They can be described as one theory whose theta angle differs by one half of the periodicity. You can imagine that their Re(tau) differs by one in a context where the natural periodicity of Re(tau) is two instead of one.

Is there a stringy realization of all exceptional groups, and a geometric realization of their S-dualities?

• The gauge theories can be obtained as a (2,0) theory on a two-torus, and the (2,0) theories can be constructed as a decoupled limit of type IIB on an ADE singularity. This gives all simply laced groups, and the other groups may be obtained by orbifolding the Dynkin diagram - which may be achieved by having an extra circle whose holonomy is the outer automorphism. The picture has been explained by Vafa and allows one to construct G_2 as an orbifold of SO(8) by the triality symmetry, F_4 as an orbifold of E_6 by the reflection symmetry, SO(2N+1) from SO(2N+2), and USp(2N) from U(2N)

Is the S-duality group always SL(2,Z), inhereted from type IIB?

• No! For example, for SO(2N+1) and USp(2N), you generate the group by "tau goes to tau+1" and "tau goes to -1/(q tau)" where q is an integer - either 2 or 3. This generates a group whose entries are combinations of rational numbers and rational multiples of sqrt(q), and this group - that carries Hecke's name - is not a subgroup of SL(2,Z) even though it is inside SL(2,R).

How can you prove such a duality geometrically?

• You can't really see it from a geometric action on a two-torus but you may nevertheless illuminate such a group in terms of a T-duality. (Your humble correspondent did not understand the exact details how these exotic groups may occur as the T-duality groups.)

Should not there still be an SL(2,Z) inhereted from type IIB?

• In some sense, yes. There are subgroups of SL(2,Z) that act as transformations that do not change the gauge group. Note that inverting "tau" gives a different group in general. If you require the gauge group to be preserved, you obtain a smaller group - the intersection of SL(2,Z) with the Hecke group which is something like the Gamma(2) group.

Can you apply these things to less supersymmetric gauge theories?

• Yes, but the details are different. N=2 Seiberg-Witten is very different from N=1. I studied in what sense the N=1 Seiberg dualities are "electromagnetic" dualities or S-dualities because the answer is not obvious due to the fact that you must flow to the infrared before the Seiberg duality becomes fully valid. The coupling runs and you're trading two Lambda scales instead.

Is the gauge group an inherent property of the theory? Do you agree with Seiberg that it's just a redundancy that is moreover not uniquely determined?

• Partially. But in some sense, with a given choice of natural operators, the theory knows about the gauge group. For example, its Wilson lines are classified by the irreducible representations of the gauge group.

Yes, but there also exist operators that are arguably classified by the representations of other groups that can be used as gauge groups in a dual description, right?

• Yes but the explicit construction of these guys is non-trivial.

How many pages the paper of EW about these issues is going to have?

• Around 300-400.

Is it a paper then?

• No.

So what is it?

• [This answer is secret and cannot be revealed to the readers.]

Hamas victory

While Canada's election results were pretty good news, the Palestinian election results are much less encouraging. As we predicted a few weeks ago, the militant Islamic political movement Hamas has easily won the polls in Palestine.

• CNN reports

What does it mean? It means that by following the policies of appeasement that never work, the democratic world has effectively given a quarter of the territory of a democratic country to the terrorists - and new plans in this direction are being designed as you read this article. Palestine has just replaced Iraq as a member of the Axis of Evil. The Arabs in Palestine were simply not ready and they are still not ready to establish a country that could become a decent member of the international community, which is why we should have avoided all such unrealistic plans.

AMANDA, neutrinos, and new physics

David Goss has pointed out a press release about

• AMANDA (press release)
• AMANDA (report by LinuxElectrons)

A system of neutrino detectors immersed deeply in Antarctic ice is measuring a single number, namely the ratio of up-going and down-going neutrinos, which nevertheless imposes constraints on new physics because various processes - such as colissions of very high-energy (typical example: around 20,000 TeV) cosmic neutrinos with the atoms of the atmosphere that may create microscopic black holes - contribute to this ratio. The ratio is more interesting than the overall number: the overall number depends mostly on astrophysical phenomena while the ratio mostly depends on particle physics that occurs in the Earth or in its vicinity. A better experiment of this kind, IceCube, is under construction.

For a flavor of this kind of physics and constraints, see

• hep-ph/0504228

and an article in the new issue of Physical Review Letters. The homepages of the projects are here:

• AMANDA
• IceCube

A more general topic: David Gross who was described as a new skeptic and sourball by a misinformation and brainwashing blog called "Not Even Wrong" - a blog addressed to those who can't distinguish s*it from gold - has calculated, during his lecture in India, that physics will be even more exciting in the 21st century and the string theory revolution is yet to come:

• David Gross in India

Gross who claims that he has been waiting for his Nobel prize only since 1994 argues that the following revolution will be even more shocking than the previous two.

All theater fans should see the new Hamlet of the 21st century, namely

• Humble boy, a fat string theorist

I would like to remind the omnipresent intellectual trash that this article is about the neutrino detectors, new physics, the waves of physics discoveries, and a theater play from 2002. If you're unable to contribute anything about these topics, you are encouraged to submit your production to "Not Even Wrong" where the s*it will be undoubtedly rated as gold. On this blog, unfortunately for you, s*it is just s*it and we follow basic rules of hygiene.

Educating girls in poor countries

According to Prof. Summers who is attending the World Economic Forum in Davos, Switzerland, the "single most important investment that we can do in the third world" is to

• educate their girls

which will lead to smaller, healthier, and happier families. Your humble correspondent who also has a 15-year old remotely adopted sister in Africa agrees that Summers' statement is quite likely to be true. My father chose to support the education of the specific girl because everyone else would be choosing cute little boys, so he had to choose...

Many people believe that there is a lower bound for the percentage of intelligent and/or educated people in the society above a certain cutoff that are necessary for the society to kick-start a growth curve and the girls in the poor countries seem to be the single most underappreciated group.

Registered partnership: The Czech senate has just approved the law about the "registered partnership" of homosexual couples. If President Klaus signs the bill, the Czech Republic will become the first post-socialist country that allows such a thing.

Future grad students

There is so much talent among the current seniors who applied for the grad school - at least those who applied at Harvard. If you consider the professional growth of a physicist, the decision to accept someone to the grad school may very well be the most selective step. The members of the committees are used to see that most of the applicants are recommended as top 1%, and in many cases it is even true. And it seems that even many people described as 1% will be rejected by many schools. It's kind of crazy.

I wonder whether there exists a more efficient way to organize the brainpower and solve most of important open problems in physics within a finite time scale. I really mean to solve important problems that people want to solve, not merely to invent a meaningful problem for everyone (and certainly not just to convince other people to work on the research direction started by you in order to improve one's ego). I can imagine that sometime in the future, the scientific community will be organized in a more diverse and interactive fashion.

What do I mean? There will be people who will be specialized in checking papers. There will be people whom you will contact to solve particular problems that they may be good at solving - for example, some of them will be ready to quickly answer some of your questions that require to use computers. Some scientific jobs will become more mechanical. In the recent era, people were forced to become rather specialized because the body of knowledge and skills that are important for the current science and technology is rather large. But they have not specialized in their methods, and my guess is that it will eventually happen much like in Ford's company in the 19th century.

Canada - a new friend

Among very many other events today, I congratulated Nima Arkani-Hamed who is also a Canadian to his new prime minister. ;-) Nima who is an N.D.P. supporter mentioned that it is great that physics exists, otherwise we would have to kill each other. :-)

Much like the relations between Germany and the U.S. improved after Angela Merkel was elected as the new German chancellor, the relations between Canada and the U.S. are going to improve, too. Two years ago when the war in Iraq was getting started, many people were predicting permanently destroyed relations between the U.S. and its traditional allies.

I have always found this thinking unrealistic. Why? It's because it was clear that eventually the situation in Iraq would come to the point in which all good people in the world simply wish the country to evolve in a peaceful and democratic direction - and the U.S. investment in the country would eventually become appreciated - and moreover it was clear that it would not be such a hot topic forever.

Another reason why the predictions were unrealistic is that the leaders of the Western countries who were against Bush did not have any good reason to be re-elected, unlike Bush himself. We already see that time is working in the right direction - the leaders of Germany and Canada have already been replaced by more friendly ones and others will follow. For example, Jacques Chirac will be replaced next year. ;-)

The left-wing activists in the U.S. often like to create the illusion that the whole world outside the U.S. supports their ideology and shares their emotion with respect to George W. Bush. Well, that's definitely not the case. There is a lot of diversity out there.

The fall of Discover magazine

When did I learn about string theory first? It was back in 1987. I used to read my favorite Czechoslovak VTM magazine ("Věda a technika mládeži" or "Science and Technology for Youth") - and I became a kind of favorite kid of the editors at that time. One of the dozens of articles that I liked was called "Six extra dimensions or a theory of everything" or something along these lines, and it was a translation of an article from the Discover magazine. (Of course, I bet that the Czech magazine did not pay a penny for the copyrights.)

Among other things, there were photographs of Michael Green and John Schwarz in it as well as explanations of what we currently call the First Superstring Revolution. At some superficial level, it had convinced me that string theory had to be right. But I could only read the actual technical articles about it when I got to Prague in 1992.

Now, 19 years later, the Discover magazine looks very different. Susan Kruglinski decided to make an interview about string theory and her idea was to pick Peter Woit. I have nothing against Peter but pretending that Peter Woit has something interesting to say about string theory is extremely unreasonable. They discuss very "important" things. For example, they talk about Peter Woit's "evaluation" of string theory which is such an incredibly famous and influential preprint that it has 6 citations as of today - about 0.2% of what the renowned articles have. If they were talking about a sh*t on the 33st street in the New York City, the interview could have been more relevant.

Just compare the content. 19 years ago, they would essentially explain you how anomaly cancellation in 10 dimensions worked. Today, they offer you completely general anti-scientific rants about scientists being imperialists, science being meaningless, theories failing to be theories, and so on and so on. No one can learn anything from such an article. It's not a theory of anything. It's not an alternative to anything.

They also talk about thousands of visitors who visit "Not Even Wrong" every day. Of course, they don't mention that 90% of the visitors are crackpots - various milkshakes, lunsfords and how all of them are called - and the rest are scientists and people who are interested in science and they mostly open Peter's blog because they find it so irritating or because they like to see some controversy.

Does it prove something about science if you have a few thousand visitors whose majority has been left behind? I also have a few thousand hits a day. And what? Daily Kos has hundreds of thousands of visitors - and still, it is a scientifically content-free blog. Does it teach you some physics or science when you read these irrelevant comments about a blog that pretends to have something to do with high-energy physics?

The article by Susan Kruglinski is what I would call an example of deterioration of a scientific magazine. Substance was replaced by discussions with undereducated outsiders whose contribution to science is based on the fact that they are popular among crackpots and the fact that what they say is controversial. I just think that it's completely wrong and it is crucial for the broader public to try to understand that Peter's opinions are just opinions of a layman - equivalent to the opinions of an average intelligent reader of The Elegant Universe by Brian Greene.

Do you think that the civilization is going up or down when the people who are paid as scientific journalists are no longer able to distinguish science from rants? Experts from ignorants? Scientific opinion from personal bitterness? Arguments from non-arguments? It's just very bad if people like Horgan or Woit are able to get that far with the kind of bullshit that they are producing. The scientific value of Peter's rants is equal to zero - but there seems to be some magical "complementary" type of a value that intellectually challenged journalists such as Susan Kruglinski are attracted by.

She also thinks that Peter is a "Dean of debunkers". I am convinced that at least in the last 5 years, Peter Woit has not debunked a single thing. They're also talking about the "alternative research" that shrank as string theory expanded. What "alternative research" does Peter offer? The holiness of the Dirac equation? Or his off-diagonal embedding of SU(2) into SU(2) x SU(2)?

What can we do about it? How should the intelligent non-scientists assure that they won't be misled by non-scientific bullshit all the time? How can they really distinguish who knows his or her science and who is just trying to damage science and confuse everyone else? I think that everyone should try to learn how to use a scientific database such as scholar.google.com. For example, if a magazine interviews a person whose opinions about a particular class of questions are presented as scientifically relevant, a careful reader should try to make a search. And compare. Of course that these numbers are not a holy word. And for the experts, they should not matter at all because they should have independent ways to evaluate statements about their field. But I am absolutely convinced that for an outsider, they are infinitely more reliable than the texts written by scientifically challenged journalists.

Imagine that someone tells you that the climate skeptics don't have a single serious publication or a citation. You search for the names of Richard Lindzen or Stephen McIntyre or someone else. Or they even tell you that Hans von Storch is not influential in his field. You just make the search or click - and you will know that you were misled because they are more influential than some of their mainstream critics. You will find technical papers about the field. Such a search can give you an idea about the chance that an outsider is bringing something interesting to a scientific field. I don't say that everyone should be using the search engines in this way. But a sufficient number of people should approach the question in this way which would prevent popular journals from publishing complete crap like this particular interview with Peter Woit.

It turns out that Kruglinski has quite a record of writing texts fully misunderstanding the scientific method. In a 2004 New York Times article, she revealed her deep math phobia.

Freezing Europe

Over the weekend, 100 people have frozen in Europe. Most of them were homeless, and 90 percent of the homeless were drunk. That includes two people in Prague; in Northern Bohemia, the temperature dropped to -30.3 Celsius degrees. Bavaria was better, with temperatures up to -33.8 Celsius degrees. See news.google.com.

Of course, these European casualties are negligible compared to the typical casualties in Asia. In February 2005, about 1000 kids died of cold in Afghanistan. The scientific explanation of the freezing people is based on global warming. The universal international solution to the climate problems is called the Kyoto protocol that has already cooled down the whole planet by more than 1 millidegree. All progressive scientists in the world - except for those who have already frozen - agree that it is a very good idea.

Let me emphasize that this news about the frozen people is sad news but without seeing the details, I am not crying despite being a very sensitive person. Such things were taking place in this world for billions of years. Our society today would be undoubtedly able to save the lives of all these homeless people for a fraction of the money that are wasted in various programs including the anti-carbon-dioxide protocols. Why are we wasting money for wrong things? It is because of ideology. If we really wanted to help the world, there would be so many methods that are so incredibly more efficient, more focused, and less ideological.

Last month we described the coldest December.

Some philosophy and/of string theory

by Robert C. Helling (helling@atdotde.de), the winning visitor #250,000

I am very happy to have this opportunity to guest blog in the Reference Frame. I thought I could use it to present a slightly longer essay on the philosophical background in the falsifyablility discussion about string theory. Regular readers here will be used to posts that are slightly longer than two sentences and arguments in favour of our beloved pet theory, although I have no intention to match the unique style of the regular poster.

The ancient Greeks introduced formal logic to be able to rigorously check if an argument is valid and to have a scheme to produce new true statements from others one is already convinced to be true. It is not too difficult to play with expressions and to concatenate them with "and", "or" and "not" (even if already at this level there are some pitfalls: At German traffic lights you can sometimes find signs saying "Bei Rot und Gelb hier halten", that advice you to stop at the indicated place at red and yellow lights rather than or).

Slightly later, people came up with an extended version of this scheme that also allowed roughly speaking the infinite concatenation of "or" and "and" using quantors "there is" and "for all". This already brings with it some of the dangers of set theory but if you are careful to specify that these always apply to elements of sets (saying "for all x in the real numbers" rather than just "for all x") you are pretty safe.

The problem epistemology faces is that empirical observations are of the first type but scientific theories are of the second type. In your lab, you observe "on this day in round #12345 of the experiment with parameters x, y, and z the measured result was 42". However, from those observations one would like to come to statements like "apples always fall down when falling from a tree" or "test-particles follow geodesics in space-time".

No matter how many observations you make (even if it could be an infinite number) you will never be able to strictly deduce a "for all" statement that is not only "for all experiments that I have done so far" but that tells you something about the outcome of future experiments.

Luckily, scientists are not logicians and take a pragmatic view on this problem being at some point sufficiently convinced that some theory is a good working hypothesis. Philosophers on the other hand have tried for centuries to formalise this process without too much success as it seems. For example coming up with statistical measures of confidence did not get very far (N.B. there might be something to learn for the landscapers) easily yielding paradoxes like the observation of a green apple supporting the thesis that all ravens are black as the latter is equivalent to all non-black things are non-ravens and a green apple is neither green nor a raven.

Progress was made on this point by the neo-positivists around Popper who emphasised that while you need to check all instances to verify a "for all" statement (or to falsify a "there is" statement) to show the opposite is much easier: If you claim that something holds for all x and I show you one thing for which x does not hold your claim is dead. Similarly, if I show you a y that fulfils some property P then I showed that "there is a y with property P". So Popper argued that a theory that offers many such potential failure modes and still survives is a good because it is predictive in a non-trivial way. This "falsifyablility" was promoted as the litmus test of scientific theories.

This sounds very nice from a logical perspective and is still very popular amongst practising scientists when quizzed on the logical foundations of what they are doing. Still, there came a blow to this attitude when Thomas Kuhn published his "Structure of Scientific Revolutions". Kuhn pointed out that although this formally sounds like a good way of proceeding, falsification is not what happens in the real worlds of science: If it did, scientists would be without theories nearly all of the time. There are many experiments that apparently disprove well established theories. For example on fun fairs you can see water that looks like it is flowing uphill. A strict falsifier would have to put his theory of things falling down in the dustbin and search for a new theory of things most of the time falling down but sometimes also up. But this is not the case. Rather, one believes in ones well established theory and investigates "what went wrong with the experiment" and eventually finds that the fact that the floor has a steep slope caused the illusion that the water was flowing up but that in fact it flows down.

Only if after a long time an experiment keeps failing and one cannot find "a reason" for it failing one will be tempted to tweak the theory and build in special exceptions that allow for this outcome of a theory. Still, usually, you just tweak the theory and keep the main body of it rather than give it up. Only if a theory gets more and more tweaked and revised and amended it becomes unattractive and more and more people will find a competitor more attractive. But such a challenge will only come from a competing theory which provides a better explanation and never from observation or experiment alone leaving one without a theory at all. Rather, people will stick with this the old, ugly, often repaired theory. The switch to the competitor is a sociological process (rather than a formal logical one) as pointed out by Kuhn and is the main subject of the "SoSR" but I will not discuss it any further here in this essay. I would just like to point out that this view is by now rather standard amongst people who think about how science is done (rather than the practitioners of science itself who often have a rather amateurish attitude in this meta discussion).

So, what has all this to do with string theory? Well, string theory is admittedly very weak on the falsifyablility side: More or less by construction at low energies it is indistinguishable from (maybe supersymmetrised version of) the standard model coupled to classical general relativity, at least we know it contains all the ingredients and I think there is no doubt that there are states (or vacua or compactifications whatever is you favourite name) in which below say 100GeV it just reproduces the standard model. You might find it problematic that it also has lots of states that do not at all look like the standard model (but for example like 10d flat space). To me this is unfortunate but not much worse than the fact that Maxwell's equations have more solutions (i.e. states) than just The Brecker Brothers playing Some Skunk Funk frequency modulated at 100MHz.

What I think is much more troublesome is that fact that if we tune into a state that looks like the standard model chances are that it won't look much different for the next couple of orders of magnitude or maybe just like a GUT. Even if we tune up the energy by another factor of 1000 (which is practically impossible for the foreseeable future given today's technology) it would be quite surprising if one finds undeniable signs of stringy physics.

Some will even claim this is true for all energies as do not really know what happens at strong coupling (unless there is a duality that maps it again to some weakly coupled theory). But at least, I think there is a consensus that weakly coupled string theory has distinctly stringy features at asymptotically high energies (like the spectrum of excited modes and Regge behaviour). Only that it will be impractical to probe these energies in accelerator experiments.

We might be unexpectedly lucky: Tomorrow, some graduate student might find a stable, testable low energy prediction of string theory. Or at LHC it might turn out, there are large extra dimensions and the fundamental scale is much lower than expected and therefore stringy features already show at scales reachable with today's experiments. However that would be quite a coincidence and we would in fact live in a very narrow corner of stringy parameter space. Or somebody discovers a cosmological imprint of stringtheory on for example the microwave background. Then there would be no question about the ontological status of stringtheory. But most likely we will no be lucky. What then?

I think, currently, expectations are a bit too high. Around the final stages of building LHC many string theorists wanted to get their share of the hype that comes with this big event of LHC being the experiment that for a long time will be the first that is very likely to see interesting "new physics" (we will be very likely learning a lot about Higgs and SUSY from it even if we will not find them, an outcome I consider unlikely). However, this "new physics" is likely to be plain old fashioned field theory and all attempts to link it to stringy or gravitational physics are not very convincing, yet. But these people have raised general expectations that, "soon, we will be able to see stringy physics" which of course is b.s..

Still, I maintain, that string theory is a very worthwhile endeavour. We know, there is gravity in the world and there is quantum theory and we cannot have both in their current form at once as they produce contradictory results when mixed together naively. So there has to be a unified theory of quantum gravity. And string theory is a candidate for it. Unfortunately, any such unifying theory has to match the limiting theories at low energies and simple arguments show that this theory will likely start to differ only near the Planck scale. So any such theory shares the above mentioned problems of string theory. This of course, unless you do something wrong: For example, if your theory breaks some symmetry like Lorentz invariance then this is likely to affect already low scales, you might find for example anomalous dispersion relations (or energy dependent time of flight) but probably you will have to hide this violation so it does not spring in your face at low energies. So even after working for forty years on string theory, people have not been able to circumvent this fundamental problem of any quantum gravity.

You could conclude that if you have very strict criteria for falsifyablility, the question for a quantum theory of gravity is unscientific because exactly of this reason. Then you are welcome to leave and go bird-watching or whatever you consider more scientific. But with such an attitude you will not likely find much left of science in fundamental physics.

Alternatively, you could decide you stay with sting theory for a little while; I argued above it is good practise in a science to stay with some theory at least for the time being until something much better comes up. And to many if not most of us, string theory is still by far the best player in town when it comes to quantum gravity. There is just no competitive alternative in sight. Everybody is welcome to look for alternatives. But this will be very hard (and this I mean not sociologically). And likely not fruitful. So, it is still a safe bet to commit most of your time and energy to string theory.

What makes me believe this, am I just the victim of the brainwashing of the physics mainstream Mafia? I don't think so. In fact, what I find fascinating about string theory is how few assumptions you have to make. You just make a small number of basic ones and the rest more or less follows (at least for almost all of the interesting developments, if you are desperately model building this might not be entirely true). It's not that with each paper, people come up with ten new hypotheses. Nearly all the papers investigate just the consequences of what is already there. And by doing this, people have found a huge number of surprises. The strongest among those are places where some circle of arguments closes. When you are able to arrive at the same conclusion on two entirely different routes. Routes that seem to be independent of each other and this "coincidence" is not merely something that was crafted into the assumptions. And string theory is full of these closed circles, in fact it is a dense network of facts that hold together very tightly.

This feature is what distinguishes it from the other approaches to the quantum gravity puzzle (if you accept that it as part of scientific investigation, see above). And this is what convinces so many people that it is powerful and there "must be something behind it".

Of course, it could all be "wrong". Then it would just be a funny mathematical theory. That alone would already be entertaining. But string theory is not mathematics. It is about gravity and about quantum theory and also about elementary particles. In addition, we have learned a great deal about the structure of gauge theories using stringy tools like the geometrisation in terms of branes. So string theory clearly is physics. Even it is not distinguishable in table top experiments from less ambitious theories like the standard model. It is really the best theory we have and pursuing such and fleshing it out has often proven not to be a waste of time.

Bremen, Germany 24 January 2006

Canada goes conservative

Well-known bloggers called cnn.com liked my title so they copied it a few hours later to introduce their article.

Canada will become a new opportunity for emmigration - but for a different group of people than in 2000 and 2004. :-) Even more paradoxically for those of us who know the former members of the Harvard Corporation, this development is mainly the work of Mr. Harper, also known as mini-Bush. ;-)

• Preliminary results
• Tory minority government

Cuba, Venezuela, and People's Republic of Cambridge are the last three countries on the continent that have not yet entered the 21st century. The main reason why The Reference Frame applauds the removal of the government of Paul Martin was his hypocritical and phony fight against the U.S. based on Martin's silly remarks about the environment.

The official results will be announced tomorrow. The Frame predicts that the turnout will be around 65%. The conservatives will get around 36% of the votes while the liberals around 30% of the votes. The 19th century socialist N.D.P. with 17% and the Quebec separatist left-wing bloc with 10% will be the only other two parties that will make it to the Parliament. That's particularly bad for the Greens with 4.5 percent. Others such as the Marxist-Leninist Party and the Marijuana Party have around 0.1 percent each.

A slight majority of the blogosphere is gonna be depressed. They will write letters to the prime minister Harper not to turn the Canadian Socialist Republic into a mini-USA. Edmonton Oilers will lose fans. Other left-wing voters will feel f**ked and they will propose a new name for the country, the United States of Canada, which is actually a good idea. A few will celebrate the conservative baby. It's always like that - someone is happy, someone else is not. The only exceptions are the systems where the unhappy people are executed.

Meeting Quantoken

Every reader of the physics blogosphere knows that Quantoken is one of the greatest geniuses ever who has figured out that we are running out of oil - and many other important insights. But how much do we know who he actually is? What's his name? Does he work as a patent clerk or something else? Where does he connect to the Internet? I could not resist the curiosity so after I learned that he lives in the Boston area, we eventually agreed to meet with Quantoken himself. He allowed me take a picture of him:



and he was a very nice guy. We have talked about peak oil, higher-derivative corrections to extremal black hole entropy and mass as well as their dual description, about the influence of Plato on Hegel, and many other things. Quantoken is far too modest to reveal all of his abilities - but because I think that being an overly modest attitude may hurt and many readers are moreover interested in his identity, I decided to post the picture despite Quantoken's requests to remain anonymous.

Tomorrow, another blogger from New Mexico who is a capitalist will visit Cambridge.

Later, it turned out that Quantoken is Chinese because he can analyze ancient Chinese poems.

When Krauss and Susskind are right

Lenny Susskind, a co-founder of string theory and one of the most original thinkers of the several past decades, has written a book that has made many physicists - including Lenny's fellow anthropic believers - upset.

The less problematic part of the book presents some ideas about cosmology and string theory that the readers have seen elsewhere. The more problematic part of the book promotes the idea of the anthropic principle in such a way that makes it clear that the basic belief in a huge number of other Universes is as religious as any other religion, although Susskind himself denies this correspondence.

After having explained that the arguments based on fine-tuning are essentially identical to those that have been used by the promoters of Intelligent Design, he also argues that this equivalence does not exist either although the explanation is not quite transparent.

Lawrence Krauss has made a comparable and possibly even more serious "sin" by having written his own book. He advocates the idea that all models and theories that require some thinking, explanations based on mathematics, or new concepts such as extra dimensions are a priori known to be probably wrong. Lawrence Krauss believes that extra dimensions are a priori ridiculous and that he can prove it without writing any papers that actually present any physical arguments: pure thought and a popular book addressed to the laymen is apparently enough. Sometimes you wonder whether Lawrence Krauss also believes that a priori it is clear that particles must have well-defined positions and velocities and that "now" must have an invariant meaning.

As you can see, one half of Lenny's book and essentially the whole book by Krauss are scientifically flawed, so you may ask: can it happen that your humble correspondent would endorse whole articles written either by Krauss or by Susskind in 2006?

The answer is, of course, a resounding Yes. It happens whenever Krauss and Susskind exchange their ideas with someone whose opinions are sillier than their own at least by an order of magnitude. Given the high intelligence of Krauss and Susskind, the number of such people is very large, of course, and one of them is called John Horgan. In this particular case, Susskind and Krauss even wrote their answer together.

• Susskind and Krauss reply to Horgan (New York Times)
  

Who is John Horgan? John Horgan is a leading science-hater. As a completely average human with common sense that is based on the 14th century agriculture, he has no understanding of modern science itself but he has been given numerous opportunities to speak with top scientists and misinterpret their words. He has also written a book called "End of Science". In this bizarre book, he argues that science is approaching its end much like the belief in science. He tries to humiliate top scientists (including Edward Witten) and twist their statements to support his basic silly claim. It is not just science that is ending according to Horgan: we are also approaching the end of progress, end of physics, end of cosmology, end of evolutionary biology, end of social science, end of neuroscience, end of science of complex phenomena, and many other ends.

Given the fact that some of these fields are really hot these days and they are expected to revolutionize our lives in the 21st century, you may think that there will be no one who will agree with Horgan's madness. But you would be wrong. And unfortunately, we are not speaking just about the crackpots from Peter Woit's blog in particular and intellectual trash in general.

A more realistic description of the situation is that there have always been people who did not believe in science. All those people who have lived since 1700 may be described by a word that starts with "ID". The year 2006 and John Horgan are not special in this respect: John Horgan is just another spot in a long sequence of billions of his peers.

Even if the progress in some particular fields slowed down - and there are many fields Horgan mentions where the progress is, on the contrary, speeding up - it does not imply and cannot imply that the belief in science as such should be diminishing. What we have learned cannot be unlearned. And as long as we are humans, no one can kill the natural human curiosity.

When I mentioned the crackpots from Peter Woit's blog, they are having a hard time with the fact that Lawrence Krauss, who was believed to have retracted all of modern physics, suddenly argues that theoretical physics is a legitimate science. It would indeed be pretty serious if Krauss or even Susskind endorsed Horgan's general moronic statements. Susskind and Krauss have helped, in a sense, a whole gallery of anti-scientific bigots including personalities such as William Dembski or John Horgan. If Susskind and Krauss were not protesting against the abuses of their books by these people, they would become two of them.

I, for one, believe that there is still a significant gap between these groups of thinkers, despite Krauss' misunderstanding for the basic motivation behind the ideas of modern particle physics and Susskind's unscientific approach to the vacuum selection problem. Susskind and Krauss are famous colleagues of their fellow physicists, Horgan is not.

I guess that the reasonable ones will continue to live in our fantasy realms where scientific arguments matter and where fantasies often become true - and sometimes they are guaranteed to - leaving Mr. Horgan in his intellectual s**tland.

Clouds rearrange

As Alex W. has pointed out to me, PhysOrg.com informs about the work of

• Prof. Philip Goode et al.

who measured the moon's earthshine to see how much light the Earth reflects. (Goode's page is here.) It turns out that the Earth is currently reflecting significantly more light than back in 2000. However, this effect did not cause cooling because the percentage of high-lying "warming" clouds has increased a lot during the recent years while the percentage of low-lying "cooling" clouds has decreased. The changes is such that the difference between the high-lying and low-lying clouds has doubled. If you don't understand how these things exactly work and why some of the clouds are "warming" clouds, be sure that you're not the only one. ;-)

Nevertheless, Goode et al. present new evidence that we don't understand the crucial mechanisms that actually decide about the significant part of the Earth's climate dynamics. Clouds matter, they are poorly represented in the existing models, and multidecadal cycles may exist.

Thanks to Mark Trodden

I don't know yet if it will work out but even if it won't, I want to thank Mark Trodden from Cosmic Variance (and from Syracuse University) for his agreement to proctor the final exam of Julia M. who had to spend the last week in Central New York as opposed to Cambridge where her completely healthy classmates were happily solving the final exam. Thanks, Mark!

The grading is also a rather hard emotional test. You know that the students don't necessarily have the highest possible score. Moreover, even those whom you really like don't necessarily achieve a high score. Not even those who learn for the exam have a high enough score. From an emotional viewpoint, it would be so much nicer to give an A to everyone. But we would then be like Cornel West. Grades are not terribly important but still, they should not become a complete joke because they play a certain role.

Lee Smolin about Nicolai-Peeters

Let me comment on Lee Smolin's remarks about the paper by Nicolai and Peeters (NP):

• On reading NP I am grateful for the hard work that they put in, but I end up feeling that they still miss the point, because they have prejudices about what a quantum theory of gravity should do coming from old expectations.

As far as I understand, the "prejudices" refer to what I normally call the knowledge of quantum field theory and its technical and advanced features such as the renormalization group or locality.

• They appear to evaluate LQG and spin foam models as if they were proposed as a unique theory which was a proposals for a final theory of everything.

No, NP analyze the ability of LQG to be a theory of at least something, namely its ability to make a single prediction, at least in principle, that cannot be obtained from the classical limit - i.e. to say anything at all about quantum gravity.

• This is in my view a misunderstanding. One should understand these as a large set of models for studying background and diffeo invariant QFT’s.

Using the terminology of physics, there exist no diffeomorphism invariant local QFTs in 4 dimensions or higher. LQG is not a QFT in the technical sense we are using today.

• These are based on quantization of a set of classical field theories which are constrained topological field theories.

When one obtains a theory with bulk degrees of freedom by modifying a topological field theory, then the topological starting point is irrelevant.

• There are three key claims: 1) these theories exist, rigorously. i.e. there are uv finite diffeo invariant QFT’s based on quantization of constrained TQFT’s.

They may exist "rigorously", whatever it means, but they do not exist "actually". On the contrary, NP explain that they fail to exist exactly in the same sense in which nonrenormalizable QFTs do not exist. This point that is simple for some of us but not for others will unfortunately appear many times, again and again.

• 2) there is a common mathematical and conceptual language and some calculational tools which are useful to study such models and

This vague "common descent" is certainly a bad thing, not a good thing. The exciting developments in theoretical physics have made, on the contrary, completely new parts of mathematics relevant (Riemann geometry; group theory; bundles; K-theory; modular forms etc. etc.). If one can show that a previously disconnected portion of math is relevant for a physical theory, it is always exciting news. And it has happened many times in the context of gauge theories, string theory, and at many other places.

The comment that the LQG papers share some general mathematical and conceptual language is a purely sociological assertion that essentially means that the LQG researchers have not had time to learn other portions of mathematics or other concepts and all of them seem to be confined by similar limitations. It is certainly not a good thing, and it does not suggest that LQG fits together. Narrow-mindedness of the mathematical methods is neither a necessary nor a sufficient condition for a physical theory to be logically consistent. These are completely different things.

• 3) there are some common generic consequences of these models, which are relevant for physics.

Such as the violation of Lorentz invariance, absence of a flat space limit, non-existence of other particles and forces, or the presence of infinitely many undetermined parameters.

• Nothing NP say questions these key claims. Unfortunately, they do not mention key papers which support these key claims, such as the uniqueness theorems (gr-qc/0504147, math-ph/0407006) which show the necessity of the quantization LQG uses.

This is nothing else than fog. These papers are purely about the kinematical Hilbert space before the Hamiltonian constraint is imposed. This is treated as the trivial part of the problem by NP. The papers about "uniqueness" have nothing to do with the actual main problems of LQG that NP study. Incidentally, the kinematical Hilbert space is not separable, and I would certainly not count it as one of the attractive features of LQG either. NP discuss this issue in the context of "ultralocality".

• And while they mention the non-seperability of the kinematical Hilbert space they fail to mention the seperability of the diffeomorphism invariant Hilbert space, (gr-qc/0403047).

Lee is trying to mix two different things and confuse the reader entirely. The uniqueness theorems above apply to the non-separable kinematic Hilbert space only. No such theorems or any other encouraging results are known once the constraints start to be imposed. When you see a kid who learns to read and a dog who learns to eat, you still have not found a dog that knows how to read. It is extremely easy to find solutions to "quantum gravity" if a subset of its requirements is erased.

• It is unfortunate that they omit reference to such key results which resolve issues they mention.

They don't resolve any of these issues whatsoever.

• A second misunderstanding concerns uv divergences. NP do not discuss the results on black hole entropy, so they miss the point that the finiteness of the black hole entropy fixes the ratio of the bare and low energy planck length to be a finite number of order one.

Except that one may derive that this value is any number we want, including numbers proportional to log(2), log(3), log of various functions of the charges of the black hole, and logs of various transcendental numbers that have been claimed to be the answer in literature. Currently, there exist at least 10 contradictory proposals what the Immirzi parameters should be. It is now known that the original papers about the black hole entropy in loop quantum gravity have been entirely incorrect - for example because they incorrectly neglected the microstates with non-minimal spins carried by the punctures. I am telling you because some people consider me an expert in this area.

• Calculations on a class of semiclassical states they do not discuss-the weave states-lead to the same conclusion (A. Ashtekar, C. Rovelli, L. Smolin, Weaving a classical metric with quantum threads,” Phys. Rev. Lett. 69 (1992) 237.).

These old papers led to the same conclusions as the results from the black holes that are known to be incorrect today.

• So there can be no infinite refinement of spin foams and no infinite renormalization. These theories are uv finite, period. This is one of the generic features I mentioned.

One can say the same thing about a nonrenormalizable quantum field theory as long as any type of cutoff or regularization is adopted. The problem is not whether the results look finite, which is a purely technical issue. The real problem is whether the regularization or cutoff introduces an infinite number of unknown parameters or whether the regularization is unique or almost unique. It is unique neither in nonrenormalizable QFTs nor in LQG, and LQG is therefore exactly at the same level as a generic UV-incomplete effective field theory.

• Thus, their main claim, that the fact that there are many LQG or spin foam models is the same as the problem of uv divergent is just manifestly untrue.

It is manifestly true for everyone who has learned the difference between regularization and renormalization.

• The freedom to specify spin foam amplitudes does not map onto the freedom to specify parameters of a perturbatively non-renormalizable theory.

Of course it does. Take all spin foam Feynman rules that lead to long-range physics resembling smooth space and assume that the space is not empty. This may be a codimension infinity set but its dimension will still be infinity. The parameters of higher-derivative terms at low energies will be functions of the parameters defining the spin foam Feynman rules. There is a one-to-one correspondence between them. The only way how you can get a different result is that you actually accidentally hit a completely consistent theory of quantum gravity - but it seems impossible because you can't really get string theory out of LQG.

• For one thing, few if any spin foam models are likely to have a low energy limit which is Poincare invariant, a property shared by all perturbative QFT’s, renormalizable or not, defined in Minkowski spacetime.

I agree. Despite the infinite number of parameters, the LQG Ansatz still misses the theories that are actually physically relevant, for example the Poincare-invariant ones. Exact Poincare invariance never works in LQG and approximate low-energy Poincare-invariance could only work once very many UV parameters (probably infinitely many) are adjusted.

• In fact, we know from recent results that in 2+1 none do-the low energy limit of 2+1 gravity coupled to arbitrary matter is DSR. So their argument is false.

Not sure exactly which of their arguments is being discussed, but the failure to reproduce a Poincare-invariant theory - something that Lee seems to confirm about LQG - is a pretty serious one, too.

• They do get a number of things right. The following are open issues, much discussed in the literature: 1) whether there is any regularization of the Hamiltonian constraint that leads to exchange moves,

It reminds me of the wooden earphones of the tribes who worship the cargo cult. Even if you modify the UV details of the Hamiltonian constraint to get rid of ultralocality, you will still not have solved the key problems above.

• 2) whether thus there are any links between the spin foam amplitudes and Hamiltonian evolution,

Imagine that in QFT or string theory, we would have serious doubts whether the path integral approach is equivalent to the Hamiltonian approach. That would be pretty devastating.

• 3) whether the sum over spin foam diagrams is convergent or, more likely, Borel resummmable (although they miss that this has been proven for 2+1 models, hep-th/0211026).

Has not it been shown by Baez, Christensen, and Egan that the sum is dominated by degenerate simplices? This fact manifests itself as a divergence in the continuum limit.

• I don’t agree with all the details of their discussion of these issues, but these certainly are open issues.

Some of them are not open anymore. One can't consider a question open many years after a conjecture has been falsified.

• NP seem to argue as if one has to prove a QFT rigorously exists in order to do physics with it, by which standard we would believe no prediction from the standard model.

The word "rigorously" is a complete bogus designed to make not-too-serious things sound serious. NP only use the word once, when they want the reader to assume that a rigorous definition of H has been given. Of course, neither NP nor anyone else wants to define these physical theories rigorously in the mathematical sense. The path integral does not exist in the rigorous treatment, for example, even though we want to use it. They are using the same level of rigor that has been standard in theoretical physics for many decades. What they care about is whether a physical theory that can say anything actually exists, not about some formalities whether one can write some formulae to satisfy picky mathematicians - which is often a very independent criterion from the question whether a theory makes sense in physics.

• They mention that there are no rigorous constructed, semiclassical states, which are exact solutions to the dynamics, but this is the case in most QFT’s.
  

If we use the word "rigorously" in the same rational way as physicists always do - and NP obviously use the physics language - the comment above is incorrect.

• This does not prevent us from writing down and deriving predictions from heuristic semiclassical states (hep-th/0501091),
  

Well, it may be that other physicists would be prevented from writing down such predictions (of violations of the rules of special relativity etc.) by certain other forces. ;-)

• or from constructing reduced models to describe black holes or cosmologies and likewise deriving predictions (astro-ph/0411124),
  

Most of us don't believe these papers but more importantly, this particular paper has nothing to do with LQG. The only relation with LQG is that some people who are otherwise counted to be LQG researchers have written papers analogous to the proposals by Brandenberger et al. But there is no LQG (new variables, spin networks etc.) in these papers.

• Nor does it prevent Rovelli et al from computing the graviton propagator and getting the right answer, showing there are gravitons and Newtonian gravity in the theory (gr-qc/0502036).

This paper assumes that nice configurations similar to smooth space dominate the path integral which is then used to derive that the path integral is approximately equal to smooth space. The reasoning is completely circular.

• But, someone may ask, if LQG is the right general direction, shouldn’t there be a unique theory that is claimed to be the theory of nature? Certainly, but should the program be dismissed because no claim has yet been made that this theory has been found?
  

I, for one, have 496 different reasons to dismiss it. Everyone can think about anything she or he wants, and others will always have their opinions whether something can come out of it.

• To narrow in on the right theory there are further considerations, all under study:
• - Not every spin foam model is ir finite.
• - Not every spin foam model is likely to have a good low energy limit.
• - The right theory should have the standard model of particle physics in it.
  

You can always sketch a program in physics in this way. One can argue that the Universe is made of little green men, and when we impose the constraint that the little green men produce the muon/electron mass ratio around 206.8, we may find the correct theory. Anyone can believe these things - but still, I think that there exists something such as rational thinking that tells us that without having any encouraging evidence, it is extremely unlikely that a correct theory may be obtained from such a highly special - yet infinitely undetermined - starting point. The Bayesian probability for such a program to work is about 10^{-2000}.

• In addition it must be stressed that there can in physics be generic consequences of classes of theories, leading to experimental predictions.

I agree with that, but in the LQG case, all of these predictions seem to be wrong (such as the violation of special relativity).

• Here are some historical examples: light bending, weak vector bosons, confinement, principle of inertia, existence of black holes.
  

These are not really generic consequences. They're consequences of theories that looked very special when they were written down. When GR was written down, it was essentially a unique theory, and it predicted light bending. Nowadays we often extend the theory but the light bending is still an effect of the same Einstein-Hilbert action as before. The same statement holds not only for light bending but also the existence of black holes. In the very same way, weak bosons only occur in very special theories. Regardless of our minor disagreement about the nature of these predictions, the example is irrelevant for LQG because it has no predictions of this kind that have not yet been falsified.

• All of these observable features of nature are predicted by large classes of theories, which can be as a whole confirmed or falsified, even in the absence of knowing which precise theory describes nature, and prior to proving the mathematical consistency of the theory.
  

In principle, I agree with that.

• LQG predicts a number of such generic features: discreteness of quantum geometry,
  

Discreteness of quantum geometry is first of all incorrect because it contradicts Lorentz invariance of local physics and other principles, but even if it were correct, one could not directly measure it, not even in principle. It's because if there is a universal law that nothing is shorter than the Planck length, the principle holds for the experimental apparata, too. In turn, this prevents us from measuring the geometrical parameters with sufficient accuracy to determine whether the allowed values form a discrete set or not. The statement would only become testable if it were translated to a scattering or another doable experiment which can't be done because the predictions of scattering can't be derived from LQG.

• horizon entropy,
  

The horizon entropy calculations in LQG have been a complete failure, starting with several papers that are known to be wrong today, continuing with conjectured links with quasinormal modes that have also been falsified, and with many other confusing proposals that contradict each other and that contradict rational thinking.

• removal of all spacelike singularities,
  

Lee seems to be obsessed with the removal of infinities. But if the resulting theory is dependent on the details how we remove them, then we have not solved any problem whatsoever. We can always impose a cutoff - in our theories as well as in particular evolution of our Universe. But if it does not allow us to say what actually comes from the singularity, then we have not moved a millimeter.

• and I believe will soon predict more including DSR, emergence of matter degrees of freedom.

I am ready to make a 5:1 bet that in the next 5 years, no one will propose a respectable framework for matter degrees of freedom to emerge from LQG. I am equally sure that no experimental evidence in favor of DSR will be found in the same time period.

• One reason for this is of course that most of the parameters in such classes of such theories are irrelevant in the RG sense, and do not influence large scale predictions.
  

If read rationally, this sentence is equivalent to the statement that we know the classical limit of GR at low energies. But this classical limit was not discovered by Ashtekar, Smolin et al. but by a former patent clerk back in 1915. Going to quantum gravity means that we actually want to learn some phenomena that are not predicted by the classical limit, and LQG can't do it. Moreover, it does not even imply the classical Einstein-Hilbert term.

• Since we know the theory is uv finite this does not affect existence.
  

As explained many times, the UV finiteness has no value if the resulting theory depends on the regulator, and LQG does depend on it.

• The lack of a uv unique theory does not prevent us from testing predictions of QFT in detail,
  

It prevents us from making predictions. We only know the Standard Model so well because we can classify all marginal and relevant operators involving the well-known degrees of freedom - there is just a couple of them - and we know that all others are very small because they are suppressed by some high-energy scale. The converse comment explains why we do not have a good (or predictive) low-energy theory of pions: it is because the terms are not under control.

We can write down non-renormalizable theories and non-renormalizable interactions, but unless we have a UV complete theory, these extra interactions cannot be predicted. They're purely a phenomenological description of the deviations from the "simpler" theory, and if we have infinitely many of such unknown interactions with coefficients of the same order, then it is equivalent to a complete ignorance. The theory is just about parameterizing our ignorance in a different way.

• and it is likely to be the same for quantum gravity.
  

It is not only unlikely: we know that it is not true. That's about the very difference between renormalizable and non-renormalizable theories. Quantum gravity has infinitely many higher-derivative terms in the effective action or, equivalently, infinitely many parameters of the Hamiltonian constraint or the spin foam Feynman rules. All of them are equally important if we want to study the physics near the Planck scale, and knowing nothing about them means knowing nothing about the Planck scale physics and/or about quantum gravity.

• The old idea that consistency would lead to a unique uv theory that would give unique low energy predictions was seductive, but given the landscape, it is an idea that is unsupported by the actual results.

Sorry but the landscape - independently of the controversial issues about its size and about its physical relevance - is not a set of different theories. The landscape is a (discrete) set of solutions to a single, unique and UV complete theory. This is not a detail but a critical point. It has been firmly established that all semi-realistic vacua that the string theorists found are a part of a single UV-complete theory. This statement is supported roughly by 5,000 papers about dualities and transitions in all corners of the string-theoretical "landscape", and saying that the uniqueness of string theory is "unsupported" sounds like an idea from someone who has lived in the vacuum during the last 10 years, to say the least.

• Having said all this, I hope that NP will put their hard won expertise to work, and perhaps get their hands dirty and do some research in the area.

They have made some work - it's just the results of their work that some colleagues do not quite like. Let's again mention that their previous paper with Zamaklar is the most cited LQG paper of 2005.

Who is an LQG expert

Peter Woit has made some strange comments about the recent review of LQG by Nicolai and Peeters. First of all, he dismisses Nicolai and Peeters for their knowledge of string theory; it should not be terribly surprising. Second of all, he expects them to repeat his own outsider misconceptions what string theory is and what string theory is not. Dear Peter, if Nicolai and Peeters were writing the same "material" about string theory as you do, then they would become the same high-energy physics ignorants as you are.

But there is one more comment that is pretty typical not only for Peter but also for others who have no factual arguments and who replace them by misleading ad hominem descriptions of the inconvenient thinkers:

• ...I’m curious to hear from experts what they think of this article...

Whom does Peter exactly mean by the word "expert"? I suppose he means an LQG expert. Who is an LQG expert? According to my understanding, an LQG expert is someone who has learned the formalism and who is able to do research of these concepts and reach some conclusions, especially if other physicists find the research relevant.

As far as I can see, the previous paper about LQG by Nicolai, Peeters, and Zamaklar that we discussed here is by far the most cited LQG paper written in 2005. Is there some way to justify that these people are not experts? I don't think so. You may define experts as those who dogmatically insist on some Holy Scripture written by someone else in the past. But in this particular case, the Holy Scripture is known to be at least partially flawed and important analyses are missing in it altogether.

For example, LQG does not solve the UV problems with the infinite amount of undetermined higher-derivative terms; it just replaces them by an infinite number of unknown terms in the Hamiltonian constraint or parameters of the spin foam Feynman rules. Everyone who has a basic understanding of the physical concepts knows that the reason is quite clear and Peeters and Nicolai's arguments are robust. Peter tries to suggest that this particular serious flaw of LQG is analogous to string theory in some mysterious way. Of course it is not and only physics ignorants could buy such a statement. String theory does solve this problem and predicts a clear structure (and values) of all higher-derivative terms, including those in the gravitational sector. This is exactly what we mean by the well-established statement that string theory solves the UV problems of quantum gravity.

Similar observations hold for the ultralocality of LQG, a fatal flaw that makes the kinematical Hilbert space non-separable and prevents ordinary notions of continuity from appearing in the LQG framework. Of course that string theory does not suffer by any of these problems either. Its Hilbert space(s) is (are) always separable and continuity - in fact, the exact physics of GR and QFT - follows from string theory at low energies.

We could go on and on and on. String theory reproduces special relativity; LQG does not. String theory is consistent with the existence of other forces and fields (which moreover seem necessary not only according to the experiments but also because of internal consistency of quantum gravity) and it in fact predicts them; LQG does not. There is no "analogy" or "equality" and whoever thinks that for every argument against LQG, there must exist an argument against string theory (that's probably the ultimate approach of political correctness), is crazy.

Peter may criticize that string theorists investigate the "landscape" of solutions and he may dislike the large number of discrete solutions. But regardless whether we understand the landscape, its size and its interpretation correctly, string theory is the first theory we ever had (and the only theory we have as of 2006) that allows us to address the question about "possible Universes" at all. In all other "theories" (including LQG), the space of possibilities is only bounded by our imagination and the time we invest to write down new terms. The space of possibilities is an infinite-dimensional continuum. In string theory, the discrete set of possibilities is made out of solutions to rather well-defined rules and can be classified. This ability to discriminate what is possible and what is not is desirable; in fact it is necessary if we want to argue that we have mastered quantum gravity. It is because in quantum gravity, we can in principle get from any "phase" to any other "phase" (think about cosmology that has no superselection sectors) and a complete theory simply must know about all these "phases"; in the stringy jargon, I really mean the "backgrounds".

Should we really use the word "expert" exclusively for those who misunderstand these basic points? Do we really want to return to the Middle Ages when the quality of scholars and their teachings was determined by the degree of their dogmatic literal belief in the Bible (or Rovelli's book or what precisely plays the role of the Bible in this context)? Should we dismiss people as non-experts just because they know evolutionary biology or string theory - or they are sinners in yet another way? Sorry if you don't like to hear it but Nicolai and Peeters are among the leading LQG experts in the current world and your humble correspondent belongs to the group that follows after them.

I confirm that the paper not only covers the most essential material about LQG that we know but it also lists fully legitimate issues with LQG that would have to be resolved before LQG could be claimed to be a promising candidate theory of quantum gravity.

There is a significant asymmetry in the relation between string theory and LQG, of course. It is very likely that no "LQG specialist" would be able to write a meaningful review of string theory that others could cite. It's simply because LQG is, in comparison with string theory, a naive game for children. Quantum gravity is a pretty specialized field and it is just a wrong idea to try to isolate separate branches that should not talk to each other. People who are quantum gravity experts - such as Nicolai and Peeters - are just naturally interested in all these questions that LQG and other approaches try to answer. So am I. And they reach certain conclusions. It is not surprising that some people whose technical errors and oversimplified and flawed assumptions are revealed don't necessarily like these developments. But it is absolutely crucial for science to move on.

If there is any controversy, it is not really between string theory and LQG. It is between narrow-minded physicists who don't want to study the insights found by others and who want to be confined in prisons defined by hundreds of their mostly incorrect assumptions - especially the assumption that the world must be a version of LEGO and everyone who thinks otherwise must be wrong because the world surely can't be more complicated than LEGO; and those who do study physics without prejudices, who are able to change their opinions and ideas by looking at the evidence obtained by others, who are ready to eliminate conjectures that have been falsified, and who actually make some progress.

And that was the memo.

Watermelons

Watermelons are green on the surface but red inside - much like the authors affiliated with realclimate.org who are green whackos on the surface but red commies inside. They have finally erased the ridiculous comment that what they're doing is not politics. In order to celebrate their new image, three of them have decided to be interviewed by "DarkSyde" from Daily Kos (the readers of realclimate.org are obviously expected to know the nicknames of all blogging revolutionaries in the world), the most popular blog among the communist lunatics (whose logo has probably been borrowed from the Great October Revolution).

Meanwhile, the performance of realclimate.org stands at approximately 11% of the performance of climateaudit.org of Steve McIntyre although there are 11 times as many authors on realclimate.org.

Review of loop quantum gravity

The previous review of loop quantum gravity was discussed here. Some of my objections to loop quantum gravity are listed here.

A new brief review of loop quantum gravity by Nicolai and Peeters appeared yesterday. They show all the nice things that many of us have been attracted by for several weeks (and some slower people are attracted by for several decades), especially the discrete spectrum of areas. The key point they emphasize is that the main problem of quantum gravity is the infinite number of coefficients of higher-derivative terms that are undetermined, making the theory completely unpredictive. They show that this infinite unpredictivity is, in the context of loop quantum gravity and spin foams, just translated into the infinite number of unknown parameters of the Hamiltonian or the spin foam rules.

This implies that loop quantum gravity and its variations make zero (0) progress in solving any problems of quantum gravity.

Nicolai and Peeters also argue that there is an important difference between lattice gauge theories and latticized general relativity. In the first case, one can independently take the continuum limit and the classical limit (lattice QCD). In the latter case, it is not possible, despite the (wrong) assumption of all the people who promote loop quantum gravity. Nicolai and Peeters use the fact that no physical semi-classical state has been found in loop quantum gravity which shows that the assumption is probably wrong.

I think that there is a more straightforward and reliable way to argue that this assumption of loop quantum gravity about the independent limits is patently false. The classical limit and the continuum limit in quantum gravity is the same thing simply because the "dynamical lattice spacing" is proportional to the square root of Planck's constant (recall the formula for the Planck length). Taking the Planck's constant to zero is therefore equivalent to taking the lattice spacing to zero. QED.

In other words, diffeomorphisms which must be a symmetry of quantum gravity allow us to convert a large coordinate distance into a small coordinate distance with a smaller value of Planck's constant, and therefore, these two limits cannot be considered separately (and the continuum limit cannot be taken as a separate step after the quantization). This is of course nothing more than the 487th argument that kills loop quantum gravity.

The 488th argument that they repeat is ultralocality - the inability to obtain the usual concepts of continuity of space from loop quantum gravity which is equivalent to the non-separability of the kinematical Hilbert space.

Weak gravity developments

There are several developments that are based on similar reasoning as the paper by Mahmoud Ahmadinejad et al.

Shamit Kachru, John McGreevy, and Peter Svrček present evidence that string theory compactified on manifolds of radius "R" always has particles that are parametrically lighter than "1/R". This is a new development in the line of reasoning that the existence of multiple scales is inevitable in quantum gravity unless everything occurs at the Planck scale. Note that their preprint number is pretty good, too: 0601111 instead of Ayatollah Khomeini's 0601001.

In a remotely related research, Cremonini and Watson argue that "beauty is beautiful" and the self-dual couplings are preferred.

Tonight, Li, So, and Wang argue that in 2+1 dimensions and probably also 1+1 dimensions, the principle of weak gravity can be proved without special arguments based on quantum gravity such as the remnants. I have not yet understood how it works. I suspect that they essentially prove more reliably the relation between the monopoles and the black holes.

Worldsheet genus from membranes

David Berman and Malcolm Perry have studied the question how the power of the coupling constant whose exponent is the Euler character arises from the membrane viewpoint.

Note that in type II (or heterotic E8 x E8) string theory, the string coupling constant is the radius of the 11th dimension (in the 11D Planck units) to the power of 3/2, up to a numerical factor. David and Malcolm obtain the correct factor by a quantum calculation that closely follows the worldsheet picture.

However, they must rescale the "6g-6" moduli of the Riemann surfaces by a factor that nontrivially gives the right power of the coupling constant. I am a bit confused why they only count the "6g-6" bosonic moduli and not the "4g-4" fermionic moduli (if we adopt the RNS formalism; the number is replaced by "2g-2" only in the heterotic case) that could potentially change the power of the coupling constant. But I guess that David and Malcolm would tell us that they must use, for reasons that I don't follow, the Green-Schwarz formalism. However, the only place where the name of Michael Green appears in the paper are the acknowledgements.

In Matrix String Theory, the correct power "3/2" of the radius comes from the dimension of the DVV operator, and the details how this result "3/2" is obtained differs in between heterotic strings and type IIA strings. So I am a bit surprised that David and Malcolm have a universal answer.

At any rate, it is conceivable that David will write an answer to this particular complaint here soon.

Another story: mathematician David Goss has pointed out an interview with his doppelgange(r) who has won the 2004 Nobel p(r)ize, namely David Gross himself.

As you may have heard from Peter Woit, string theorists have learned from the global warming "scientists". Their classic Stephen Schneider has described the necessity of fraud and lies in climate science as follows:

• ... And like most people we'd like to see the world a better place, which in this context translates into our working to reduce the risk of potentially disastrous climatic change. To do that we need [Scientists should consider stretching the truth] to get some broadbased support, to capture the public's imagination. That, of course, entails getting loads of media coverage. So we have to offer up scary scenarios, make simplified, dramatic statements, and make little mention of any doubts we might have. ...

Because of some recent mis-pronouncement that have been easily mis-interpreted as abused by septics such as Peter Woit, David Gross - who is otherwise a great optimist and a person who can appreciate the work of others - was criticized by the so-called scientific consensus and the central committee of the secret police of string theory. He was forced to give an interview in which he suppresses all doubts about string theory, in agreement with Schneider's principle of balance between the truth and politics. (And the journalist "improved" the interview so that GUT and TOE were treated as synonyma.)

Of course, I am joking - string theory is on the contrary one of the few scientific disciplines where it does NOT work this way. ;-)

At any rate, I am happy that a reader of both Peter Woit's blog as well as mine has discovered that some recent comments about David Gross's attitude to string theory on Peter Woit's blog have been complete crap. It will still take a lot of time before people realize that the rest of Peter Woit's statements about string theory is also bullshit, but there is a lot of time for these developments.

Back to Northeast

Seattle has been fun. There are many interesting, skillful, and smart people over there from many fields of physics. This list includes not only very good theorists but also some renowned experimentalists such as Eric Adelberger who also attended my seminar and, not surprisingly, remained skeptical about string theory as such. Well, the talk was not designed to convert infidels but rather explain why and in what sense gravity should be the weakest force.

We have also had some beer with fellow Czech V.R. - greetings!

Those 24 hours of flight in total have been rather exhausting, too, especially because there is a lot of work waiting here in Boston: the final exam on Thursday, 485 folders with applications of PhD student candidates, and many other things.

On Monday night, I could not resist to see the city from the space needle. Unfortunately it was raining bad. One of the insights is that if you visit the Washington state, you should be careful what is written on your hat. What do I mean?

Instead of the imperialist hat with the American flag and a hawk, I was wearing a "Washington Redskins" hat (one that was incidentally bought in the Czech Republic many years ago). For those of us who are not NFC fans, there was about a 50% Bayesian probability that it was a team in the Washington state. But as you know very well, Bayesian probability is bullshit from the scientific viewpoint. Indeed, the Redskins are located in Washington, D.C., and the hat confusion had profound consequences because the Seattle Seahawks had just lost to the Washington Redskins or the other way around - whatever. :-) (Sorry for the inaccurate coverage of these important sport events.) Consequently, I could not get various discounts on the space needle and some other people felt anxious about the hat, too. :-)

The power of propaganda

An important part of all totalitarian systems is an efficient propaganda machine. The very purpose of this structure has always been to protect the "official opinion" as the only opinion that one is effectively allowed to have. Whoever disagrees with such an "official opinion" must be destroyed either physically or by the propaganda machine. If an execution is not an option, he or she must be stripped of the very basic human dignity.

In the 1970s and 1980s, dissidents in Eastern Europe were no longer executed - but the propaganda machine was running at full steam. A useful example from Czechoslovakia were the Plastic People of the Universe, quite possibly the greatest obscure rock band of all time. Its members were relatively average people with a deep interest and somewhat extraordinary talent in music. Some of them were married - and reportedly great husbands - some of them were single, most of them had no experience with crime whatsoever, one of them had had a single physical incident on his record, and they represented a broad scale of rather ordinary jobs. They were not drug addicts either. Because they promoted the Western values and a different music genre than the official one, they were permanently prosecuted by the communist regime, banned, and jailed. The communist newspaper "Rude Pravo" (Red Law or Red Right) - a leading newspaper in the country - was consistently describing them as criminals, drug addicts without a proper job - simply losers that everyone else must avoid.

Václav Havel allowed them to play on his farm and he was so shocked by the trial against the Plastic People that he decided to do something about it. In fact, this is how Charter 77, the dissident organization, was created in the first place. Needless to say, Havel and others became a target of the propagandistic attacks, too.

Havel was always described as an asocial son of a Nazi family (a very misleading description of his parents - a respected capitalist family) who is an alcoholician and his other physical parameters were analyzed in detail in order to induce hatred among the readers. You know that Havel probably always liked beer (and cigarettes, like many other people) - and we may add other criticisms (and I am the last one who would imagine that the dissidents were perfect) - but he probably was not that terribly asocial if he could become a president for nearly 13 years and one of the world's top intellectual authorities of the late 20th century.

Even if you notice that Havel's lifestyle and physical dispositions are far from being extraordinary, you must kind of feel that these observations don't make a communist regime more acceptable. Havel's beer can't change the fact that the regime was wrong.

Needless to say, all this propaganda was designed in order to personally damage the politically inconvenient people (and their families). Although there always existed people who endorsed such an approach, I hope that today, most of us - including the people of Eastern Europe - find a similar attitude of the governments against its own citizens unacceptable.

But there will always exist people with a deeply totalitarian way of thinking who simply find the very existence of other opinions unacceptable and who will always be ready to go after those who bear different opinions, infiltrate their personal lives and anything else that can do the job - and they will actually do so as soon as they get the opportunity. Indeed, they don't find it sufficient to dismiss the arguments they don't like. They will try to connect these arguments with everything else that they may find helpful to damage those who bear the inconvenient ideas and insights. Everything seems OK with the life of the person whom you don't like? Try to go after his or her family, childhood, and if you don't find anything against them either, just invent it.

Unfortunately, this is also the case of the recent debates about the "innate aptitudes". What kind of an answer to the thoughtful, convincing, and quantitative statistical and neurobiological analyses do you expect from those who prefer the naive paradigms of universal egalitarianism? Try this one:

• The wrong side of history

The author believes that those who don't like his reptile ideological anachronisms about egalitarianism from the 19th century - something that many of us have considered to have been essentially dead for several decades - are on the "wrong side of history". Right. But that's not the peak of that article. The main "argument" in that text is that the people who disagree with the author's childish version of egalitarianism are surely discriminating against various groups all the time. Moreover, he even accuses them of thinking that women are beautiful. Imagine the breathtaking crime! ;-)

The author's analysis is so "deep" that he also describes how the adolescence and the social skills of the people with different opinions than his own, including their ability to play American football, had to look like. Imagine that he is correct and many of us are really bad players of the American football. (I have not asked Steve Pinker.) Imagine that some of us - like me - had never sports as their highest priority (as opposed to music, science, and similar things) and with a few exceptions (such as high jump or long jump in my case), they were never among the best athletes among their peers.

Imagine that some of us - and this is really not me, according to all testimonies - have discriminated against colleagues of the opposite sex once or twice. (We're really putting a very diverse group together and be sure that a unified description of their social attitudes and favorite sports won't work.) I still don't follow how these possibilities might contribute as a rational argument in the debate whether the cognitive skills of men and women differ.

As far as I can say, they can't contribute a millimeter because they are as independent from the actual truth as Havel's beer and poor health is independent from the question whether the communist regime was right. Only completely stupid people can think otherwise.

Of course, every piece of crap will find its readers - and several readers with IQ below 60 have applauded the author. The message of this article for me is absolutely different and not really new. The message is that the left-wing ideologies have always been, they are, and they will always be inherently totalitarian in nature. Egalitarianisms of all sorts are about the denial of reality, the actual differences that imply many other differences and break all possible naive symmetries that you may imagine to exist between complex objects in the world as long as there is any freedom in such a world.

In a free society, it is all but guaranteed that people will choose different activities and their level of success will be different, reflecting not only their efforts but also their talents and other pre-determined quantities. Also, people will have different opinions about the origin of various social phenomena.

And the only way how reality may be denied and how one can impose the - completely unnatural - egalitarianism in talents, outcomes, as well as the uniformity of opinions (which is what the author obviouly not only wants but finds extremely important) is to execute political power, attack the inconvenient people ad hominem, and promote dishonest and intellectually defective arguments like those in the article "The wrong side of history". The author who has revived the worst methods of the notorious totalitarian regimes should be deeply ashamed.

The article I mentioned is what I call the ultimate breakdown of moral values and of the rational approach of the author.

Seattle and AdS/QCD

Our friends in Seattle seem to be really good with the gravitational duals of QCD and many related questions, and I plan to write something about the interesting things that Andreas Karch and Matt Strassler told me about AdS/QCD and some issues of the LHC later.

It's raining here and the weather has the ability to affect the impression from any city. The first time when I visited New York, it was also raining - and I obviously liked the City much more when it was sunny.

Andreas told me about the successful calculations of meson masses from the holographic perspective. One considers a dual free theory whose structure is more or less dictated by symmetries; she writes down the bifundamental scalar fields that break the chiral symmetry down to the diagonal subgroup. The result is surprisingly good - five or ten percent errors of the meson masses despite a very small number of input parameters.

The three-point functions and higher do not work as well, and the properties of QCD objects that really look like strings - especially those with spin 2 and higher - also don't work too well. Of course, a question is whether the surprisingly good agreement concerning the masses (two-point functions) of the low-spin QCD mesons is just an example of a good luck, or whether we can find some arguments that it is a reflection of some underlying "truth" whose other predictions could also be trusted. It has not been quite explained which of these things should work and which of them should not and why.

Matt Strassler agrees with this broader picture and it is one of the reasons why he focuses on model-independent things.

Matt also argues that the LHC should not be thought of as a gluon-gluon collider. In his picture, the number of very interesting events with very high center-of-mass energies could be dominated by gluon-quark scattering. So we exchanged some ideas and scalings concerning the parton distributions of quarks and gluons (and less importantly also antiquarks) inside baryons, with Matt of course being the much better knowledgeable party in the discussion.

In QCD, the couplings of an excited (spin one) rho' mesons seem to be pretty universal, up to small errors, and this fact can be explained from the dual theory because they correspond to the lowest mode of a five-dimensional gauge field in a cavity whose profile has no zeroes. The relevant couplings are obtained from overlap integrals and if you know that the profile has no zeroes and behaves in a more or less pre-determined way in one extreme region, the result for the profile - and consequently also the overlap integrals - is determined and therefore universal, up to small corrections. That's the reason why the three-point couplings of rho' seem to be pretty universal while you could not say the same things about the ever higher excitations.

Leaders of mature nations

Martin Luther King was alright. Still, I feel that the modern nations and ethnic groups in 2006 need slightly different leaders.

Because many people who disagree with my politics often try to remind me of the discrimination against the Czech nation - which is a complete non-issue for me, of course - let me tell you a story about the Czech national revival.

Let us start with some pre-history.

The Slavic culture started to influence the Czech lands sometime in the 8th century or so. In the 9th century, the territory was organized as a wealthy and cultural empire of Great Moravia - an ancient prototype of Czechoslovakia. Actually many of the Czechs could have been Alpine Celts, but that's a different issue. Constantin and Method were invited to Great Moravia in 863 and brought an alphabet and Eastern Christianity. However, the influence from Germany became more important very soon and the Czech lands became a standard part of Western & Catholic civilization.

The Czech kingdom was established around the 10th century. The royal dynasty was officially and permanently accepted by the Roman Empire in 1212 (through the Golden bull of Sicily). Many nice things happened in between - for example, the Czech king (and German Emperor) Charles IV founded the Charles University and many other things in 1348. In the early 15th century, 100 years prior to Martin Luther, Jan Hus started to reform the Church. Unfortunately he was burned at stake in 1415. His disciples named Hussites, an organized group of primordial communist rebels who shared everything and whose methods of fight were pretty sophisticated, has made successful attacks against the catholic countries around. It is always a difficult issue whether the Czechs should be proud about them - were they heroes or communists combined with terrorists? - but I am pretty sure that most of the Czechs are proud after all. ;-)

But I want to get to the "dark ages". After many minor victorious battles, the Czech reformers etc. had lost several key battles (1434 and 1620 were the most important ones) and three or four centuries of German dominance started. The Czech language essentially became a language of peasants. All intellectuals had to learn German if they wanted to make any difference. The Austrians and Germans skillfully used the argument about the German cultural superiority. There were serious doubts whether the Czech nation and the Czech language would survive at all.

These doubts were stopped in the late 18th century when the national revival began, much like in several other countries of Europe. A group of intelligent patriots started to write a lot of books, fill in the missing words in scientific terminology, compose symphonies with national themes, establish new theaters, and so forth. They were pretty good even though I still feel that the American founding fathers were more sophisticated still. Nevertheless, it became clear in the early 19th century that the Czech nation was not going to die after all. However, the argument about the German cultural superiority was still there. How did the people deal with it'? Most of them simply accepted it because it seemed to be true.

However, there were people who did not want to accept it. Shockingly, in 1816, a 27-year-old poet Mr. Josef Linda discovered a manuscript of the Vyšehradská song, a poem in archaic Czech language that was soon afterwards classified as a work from the 13th century. One year later, a 26-year-long-old poet Mr. Václav Hanka discovered the Královedvorský manuscript, apparently also from the 13th century. Another miracle followed one more year later: an anonymous package sent to the Czech Royal Museum in Prague contained Zelenohorský manuscript, seemingly from the 9th or 10th century. (All these manuscripts are named after the places where they were discovered.)

All of these works are magnificent and be sure that when you look at them, you won't see anything wrong about them. The cultural gap between the Czechs and Germans had been erased since the Czech manuscripts were as old and as good as the German ones. Or was it?

This question has divided the Czech patriots into two groups. Most of them believed that the manuscripts were genuine. Or at least they claimed so. Prof. Tomáš Garrigue Masaryk who became the founder of Czechoslovakia in 1918 and the country's first president had a different opinion. He - and other "realists" - had various reasons to be convinced that the documents could not have been genuine. He had incredibly reasonable opinions about a whole sort of questions which allowed him to be a leader of the only Western-style democracy in the totalitarian sea of Central Europe (the description of Europe is as of the 1930s).

Modern day tests in the 1960s based on methods including X-rays and fluorescence have proved that all the manuscripts were fabricated. Masaryk was right; the majority was wrong. In some sense, I admire Hanka and Linda - or whoever else created them. It can't be too easy to doctor manuscripts that are supposed to be 600-900 years old. But I don't share their moral attitude. The manuscripts are still nice - but they are pieces from the early 19th century, not from 9th-13th centuries.

What is the punch line of this story? The punch line is, of course, that different nations and other groups don't necessarily have the same glorious history of their old literature and other things. The first plays and books written in Czech are a tad younger than the comparable German, English, or French ones. Still, a realist academician or politician - such as Prof. Masaryk - is able to accept this observation. And by accepting the truth, he may make it easier to inspire some progress. By the 1930s, there was again little doubt that Czechoslovakia was one of 10 most advanced modern countries in the world - a fact that was unfortunately modified by the subsequent developments.

Of course that the Czechs today have no problems to admit that the Germans may be or may have been "better" in various respects. This fact partly reflects the Czech national "submissiveness" - but even those Czechs who are far from being submissive are able to admit that the weakness can be on our side (except for those who dream about the old good times of communism, because they always blame someone else, but that's a different issue). Every mature enough nation must be able to accept reality - and the reality is full of differences of all possible types. Only by acquiring the principles that the "superior" side is using, one can get at their level (or above it).

GRBs and dark energy

There have been reports in the media - and a discussion at Cosmic Variance - that according to some observations of B.S. from Louisiana, the cosmological constant is not constant after all. Instead, it seems to be changing with time. It has been argued that this is implied by the observations at the 97% confidence level.

The corresponding equation of state would give "w" (the pressure/energy_density ratio) smaller than "-1" (much like in models of phantom energy) which would violate the dominant energy condition - and potentially allow superluminal signals. This sounds highly suspicious. Gamma ray bursts had to be used for the analysis - and they are sufficiently poorly understood - and independent experimental astrophysical sources at Harvard also recommend you to ignore the news.

One year later

Exactly one year ago, on January 14th, 2005, President Lawrence Summers spoke to a conference whose goal was to study questions related to the underrepresentation of women among the scientists and engineers.

He said - very carefully and with disclaimers that he was going to be provocative - something that 99% of Europeans and most of the U.S. neurobiologists, among many other groups, find obvious: the differences probably have something to do with biology. There is absolutely no doubt that the president has had not only all the rights to say what he had said, but in fact, it is exactly this kind of questions, hypotheses, and arguments that the conference should have studied in the first place. If the conference about "Women in Science and Engineering" were designed to do anything else, one should describe such a conference as an exercise in hypocricy and as a waste of taxpayers' money.

As you may expect, no one cared whether someone throws away millions of dollars for bogus conferences that don't even touch the very basic questions that define their purpose. Instead, what many people did care about was Summers' "heresy". A very difficult year for all of those who prefer a rational approach to all questions - including the questions that some people may find sensitive - was just getting started. Our faith in humanity has been hit hard, using the words of the president.

After some time, the president started to apologize. At some moment his apologies seemed to be so authentic that I started to contemplate the hypothetical possibility that the president had changed his mind, indeed. He could have been given some special drugs by the secret PC policewomen and policemen or something along these lines. ;-)

It was not a terribly convenient class of ideas to consider. If not even the distinguished president has the right to mention a trivial point that different outcomes could be a consequence of different initial conditions (and it really started to seem that he does not have this right), what do you think about the academic freedoms of more junior scholars? And the freedoms of those who may even choose, unlike the president, the "wrong" political party?

The apologies that I was forced to make myself as well as those by the president were extremely demoralizing. The situation was completely analogous to stories in many different totalitarian regimes. After the Soviet Union occupied Czechoslovakia back in 1968, terminating the Prague Spring, various people "had to go" and some bosses stayed, trying to do their best in the context of neostalinism, as many of them argued after 1989. What is the degree of collaboration that you allow your favorite person to accept before you start to lose the faith in himself or herself?

It turns out that the weird theory about the drugs was not that weird after all. Zachary Seward describes the huge amount of pressure that various people, including the advisers, exerted on the president. I wonder whether Mikhail Gorbachev had ever experienced a comparable amount of pressure from Brezhnev's soulmates when he planned to end the cold war and reintroduce some glimpses of democracy, human rights, and market economy into the Soviet Union.

Seward's article explains the "consensus" that all the advisers believed: Summers had to apologize and such apologies would stop the conflict at the beginning. I think that the actual history shows that the advisers were being incompetent. Almost every surrender to aggressive forces whose goals are revolutionary - and include a drastic reduction of the academic freedoms in order to establish a new "official opinion" - is a mistake that inevitably leads to escalation of their plans. This case was no exception.

What should have happened instead is that well-known people from various fields, especially those who are convinced that Summers' "hypothesis" was probably correct, should have been invited to speak about this issue at Harvard, in order to dilute Summers' personal responsibility for these statements. The very basic rules of the scientific method - and the academic approach to questions in general - were at stake. That is not the best opportunity for cheap decisions and fabricated apologies. What did the apologies lead to? They acted as threats for all those who shared Summers' viewpoint. Consequently, most of them were forced to be largely silent, which intensified the apparent and largely fictitious isolation of the president.

Living with the laws of Nature

Finally, I want to address the assertions that the politically correct people are somewhat "nicer" than other people who were doing the very same evil things in the past. In my opinion, it is mostly bullshit. Every organized group of people who believe a certain ideology is convinced that their beliefs are essential for the existence of life - or at least for a decent life of the humans - and this is why it is legitimate to suppress people's freedoms and occassionally replace the truth by lies in the name of their "great" vision.

The decrease of the influence of Christianity may have brought various negative by-products with it, but we have certainly ruled out the conjecture that geocentrism or creationism was necessary for the survival of the society and its moral values. Whenever we learn something about Nature or the society - such as the ideas about heliocentrism, evolution, or cognitive differences between the sexes - it can never destroy our life by itself. We are living in a world that follows certain laws and we know that these actual laws are compatible with the existence of life. (Our anthropic friends even argue that this tautology should be used as a starting point to do physics.) But at any rate, this implies that it can't ever permanently hurt to learn the truth.

Is the natural percentage of women in computer science twice as small than what we actually have today? Maybe - is it a disaster when we learn such a thing? Do you want to nuke the whole civilization whenever you learn that Nature does not follow some of your preconceptions? Will you start to hate women as soon as you learn that they're less prepared for computer science in average, after all? Do you hate dogs because of the same, but much more pronounced reason? When we learned that CSL-1 is not a double image created by a cosmic string, should we have tried to hide the answer because the "Yes" answer is nicer? I hope not! ;-)

Nevertheless, this honest mode of reasoning is plain impossible for many people. Just like William Dembski believes that by learning evolutionary biology, our world becomes a bad place to live, which is why he finds it so important to promote his creationism in the cheap tuxedo, the politically "correct" people believe that by learning that there are genetic differences between various groups of people, we are destroying our civilization, too. Of course that it's bullshit. If we want to make the civilization as good as possible - and to help all of those whom we like as efficiently as we can - we must know the truth. How do we learn the truth? We consider possibilities, state the conjectures, falsify the wrong ones by actual experimental tests, induce more general theories out of the individual conjectures that have passed the test of time, and deduce their consequences in other contexts.

The main difference between the radical politically "correct" movements and the notorious totalitarian ideologies from the past is that the former have not yet found a country whose government, legislation, and courts would be completely controlled by the politically "correct" ideology. Thanks God or Nature (or thanks to the fact that we only live in 2006 which has not yet seen such a system).

Systinet sold for $105 million

The Burlington, Massachusetts - based company Systinet producing SOA that was founded by Roman Staněk in Prague in 2000 has been sold to Mercury for 105 million dollars. Congratulations to Roman!

As far as I remember I've met Roman Staněk only once - in Grendel's Den, a pub here in Cambridge. He came there with Radovan Janeček whom I have known from the Liane BBS for years.

Roman Staněk's new Czech blog is here. Radovan Janeček's English blog "Nothing impersonal" is here. Many people expect that the Czech media won't inform about the deal, and if they will, the comrade Paroubek, the current prime minister and Joe Quimby's twin brother, will send cops to put Mr. Staněk in the prison. ;-)



Figure 1: Paroubek and Quimby. If you have problems to tell them apart, remember that Quimby is wartless.

Supersymmetry breaking

I recommend everyone the review of "Supersymmetry Breaking" by Yael Shadmi that finally brings some of the secrets of anomaly-mediated supersymmetry breaking (and the relevant references) to the mortal stringy human beings - secrets that have been largerly hidden in the hep-ph archive.

The main punch line is that the anomaly-mediated supersymmetry breaking is the most beautiful way to communicate supersymmetry breaking - which must originally occur in the hidden sector (MSSM itself is not enough). It induces no flavor changing neutral currents (unlike gauge-mediated and gravity-mediated pictures) and predicts the masses of all superpartners up to an overall scale factor. All these terms arise from the scalar auxilliary field in the supergravity multiplet that breaks superconformal invariance. And the ratios of masses only depend on couplings, beta functions, and anomalous dimensions of the MSSM.

The only "small" problem with the minimal anomaly-mediated SUSY breaking (AMSB) is that it predicts tachyonic slepton (and probably squark) masses. So the minimal AMSB does not work. It can't be fixed by new physics at high scale because AMSB is highly predictive.

There are two ways to fix it:

• using higher-order effects in "F" - the scalar auxilliary field in the SUGRA multiplet
• adding new fields that are light before SUSY breaking

To see a recent example of the second approach, you may try a recent paper by Linda Carpenter. She only needs one new hidden U(1) - you can imagine that it comes from the M5-brane in the strongly-coupled Heterotic MSSM by Braun, He, Ovrut, and Pantev - and one parameter to be fine-tuned. No bad couplings are generated. The hep-ph arXiv has a lot of work dedicated to these issues.

Supersymmetry is beautiful, and with AMSB, it's beautiful and highly predictive even after it's broken which is why I am still proud to have made the $1,000 bet on the discovery of SUSY by summer 2008. ;-)

Wolfram's plans for particle physics

Stephen Wolfram has shown us the new version of Mathematica - currently something like 6.0.2 - as well as his new kind of music and other interesting things. He also proposed various exciting ideas how a new computerized system that would become a standard to deal with particle physics could be created. A long discussion about the suitable type of physics-friendly computer geeks who could develop such a system - and their expected salary and background - followed.

Finally, Stephen Wolfram reiterated his ideas about the Universe being a cellular automaton. In the atmosphere of complete harmony, Nima advocated a meta-unification. According to Nima, Stephen Wolfram's picture of slightly different cellular automata giving vastly different physics is very close to the landscape reasoning. Well, it was a stimulating debate but I don't have to hear everything in the world, so eventually I got inspired by Nancy Hopkins (at least for a while). It is indeed true that my overall sympathy to both of these ideas are comparable, too. ;-)

If you're interested in the more precise isomorphisms between the cellular automata and the anthropic principle, there is a cute analogy invented by Nima that looks as follows: the negative cosmological constant is mapped to the automata that die out (big crunch) while the large positive cosmological constant is mapped to the trivial (solvable) automata - and the nontrivial automata that don't die out represent the anthropically allowed window for the cosmological constant. :-)

The world could indeed be a "new kind of" a cellular automaton, except that the "automaton" used in the real Universe is not classical; it is not discrete; it is not non-relativistic; its identity is constrained by different rules than algorithmic rules; and it differs from "cellular automata" in all other essential aspects, too.

CSL-1 is not a cosmic string

I received two messages about this sad news almost simultaneously - from Mark Jackson and Joe Polchinski. Guiseppe Longo (and maybe his collaborators) has downloaded the pictures from the Hubble Space Telescope, and it is "just a pair of interacting ellipticals sitting in a rather faint cluster," not a cosmic string.

• See the postscript version of the same image
  

He promised various people to be informed quickly, which is why you are informed so abruptly by a leading physics blog (one hour before our colleagues at Cosmic Variance) even though the news is not the most thrilling outcome you could have hoped for.

At any rate, it is time for science-haters to celebrate. ;-)

Some people ask how the picture would look like if there were a cosmic string. I think that it would look like this one:

Let me add to the main text that Joe Polchinski's estimated probability that a cosmic string could be seen was something about 10%. Joe would have therefore told you a smaller number for this particular case, I think. In this sense, it is not a surprise that the conjecture that CSL-1 was a cosmic string was falsified. While it is not a surprise, it is still a disappointment.

A confirmation that it is a cosmic string would have meant much more obvious progress. This observation has falsified one particular case but it has not falsified the idea of cosmic strings in general. And just to be sure: it has of course told us nothing about the validity of string theory as a fundamental theory.

Herman Verlinde's picture

The LHC olympics people from the whole East Coast have come to Harvard to play their games and listen to various lectures about the evaluation of the fictitious LHC data that is going to become real data in less than two years.

That's a good opportunity for interesting debates - even for those of us who are very busy right now.

We have talked with Herman Verlinde and it was fun. First of all, we were teaching the same course (Quantum Mechanics II) so we were exchanging experience with quantum computers, entangled states, and Herman taught me about the three-spin-1/2 "GHZ" state that maximally violates locality in the EPR sense. Very interesting.

Decoupling of open strings

Herman has also explained the true nature of the "bet that string theory is correct" that Peter Woit copied from P.P. Cook's blog. The reality was a bit different and more technical.

Herman argued that it would be unreasonable to bet against the statement that open string theory contains the Standard Model. Why did we use the adjective "open" in the previous sentence? Herman proposes the following picture:

• it is extremely unlikely that the accelerators such as the LHC that will be available in the near future will measure anything such as quantum gravity
• this should mean that gravity, an important part of closed string dynamics should be decoupled
• he believes that the rest of physics - the Standard Model and beyond - should therefore be interpreted as decoupled dynamics of open strings
• open strings propagating around a specific singularity could and should give you this Standard Model or its extension
• quantum gravity and the Planckian completion is obtained by embedding the singularity into a bigger theory - a compact "Calabi-Yau" manifold
  

This line of reasoning of course does not prove that other scenarios - where the Standard Model is made of closed strings or other objects - are impossible. But it may be the most natural and "minimal" decoupling of gravity from the rest. Moreover, Herman argues that in this picture, it is more or less guaranteed that the QCD string should be identified with the fundamental closed string. I still don't quite follow why it must be the same type of the string, but it is conceivable that he has an argument.

See their paper with Martijn Wijnholt for a specific construction of the Standard Model on a D3-brane.

Incidentally, Herman also says that in the decoupled picture of particle physics, gauge-invariant fields like the parameters of the Standard Model don't acquire any potential - since the potential is inherently a closed string effect. This would mean that getting the right spectrum is enough to find a realistic candidate. The couplings are only determined once the compact manifold and the closed string field stabilization is calculated. So you have a theory that you can't prove or disprove for some time - a "not even wrong" theory - which Herman believes to be essentially a good thing.

Black hole final state

If you're more interested in the illusion of Intelligent Design, you can read this interview with Lenny Susskind who has his predecessor on his T-shirt. ;-) As the reviewer of the Cosmic Landscape at amazon.com wrote, this book has certainly energized God.

Eva Silverstein and Gary Horowitz have submitted an interesting paper that extends the research of the tachyons in cosmology and their impact on topology of spacetime. We talked about these things in the article about the theory of nothing.

One of the potentially far-reaching consequences of Eva's and Gary's paper is that they seem to have found some stringy realization of the black hole final state by Horowitz and Maldacena. Recall that Horowitz and Maldacena try to explain the information loss paradox semiclassically by saying that the information is not lost in the Schwarzschild singularity because all matter converges to a unique state near the singularity - the black hole final state. This is why no information really "crosses" the spacelike singularity inside the Schwarzschild.

In some sense, the matter propagates outside the black hole before it falls in. Then it continues inside the black hole to the singularity, bounces off the singularity because the unique black hole final state translates the incoming states into outgoing states. Then the matter propagates backward in time inside the black hole before it reaches the horizon and transforms into Hawking radiation that escapes to infinity. As you can see, the arrow of time is heavily violated near the singularity because normally we are only allowed to define initial states, not final states. Unitarity is preserved in the picture above because everything evolves with "time" in a unitary way except that this "time" goes back and forth in the real time, in some sense.

Preskill and Gottesman argued that once the interactions are taken into account, unitarity will be lost in the Horowitz-Maldacena picture anyway because the two Hilbert spaces of matter inside the black hole - that are used for the incoming and reflected matter, respectively - are no longer decoupled. These interpretations of the picture are due to your humble correspondent, but I believe that they capture the points of both papers.

Horowitz and Silverstein now argue that in perturbative CFTs with some tachyons, the black hole final state can be given quite an explicit form.

Because we talked about the information loss issues, I should also mention that tonight, David Lowe and Larus Thorlacius propose a plausible description of non-local effects in gravity that are small enough not to violate causality measurably but sufficient to preserve the information.

Neil French and the two eras

Neil French, a hero of the British advertisement industry of the 1970s, is a Gentleman from the old golden era. It was an era when a single man - and, indeed, it was usually a man - was able to change the world. An era when the same single man could take a responsibility for his acts. An era of colorful Gentlemen who actually had some beliefs, goals, and idiosyncracies. Gentlemen who were ready to sacrifice something because of their dreams.

As you know, we live in a completely different era these days - and let us hope that it is temporary. We live an in era of political correctness. An era controlled by committees and average people without any special features. An era where everything that differs from the average must be eliminated because it inevitably offends someone. And if something offends someone, it must be bad, many people believe. An era when people don't have any real beliefs or big goals. An era in which the responsibilities are shared. An era of breathtaking hypocricy.

You can imagine what happens if these two eras interact with each other. ;-) In October, Neil French was asked in public why there were so little high-ranking women in his field of advertising. He apparently supposed that it was an actual question, so he gave them an actual answer that reflected several decades of his extensive experience from his field of expertise:

• "Women don't make it to the top because they don't deserve to. They're crap. Women inevitably wimp out and go suckle something."

As you can see, this is not quite the language we typically use in Academia during conferences. :-) Nancy was "partially paralyzed"; in this particular case, it was Nancy Vonk. Neil French was trying to save the situation, so he accused Miss Vonk of

• "getting her knickers in a twist."

As you can guess, he had to resign. To make things clear, I am in no way supporting French's particular language or ideas. But on the other hand, I can figure out that this had to be the man who has created so many catchy slogans. His creativity is too much of a good thing for the current era, so this Gentleman had to be sacrificed. Note that there has been no visible revolution that has started this era. No laws have been codified that would make it illegal for Neil French to explain how the people from different groups interact with his industry. Nevertheless, such pronouncement have gradually become "effectively illegal". And that's another bad feature of the present: the written law is becoming secondary because we are under ever increasing pressure of various "additional unofficial laws" that are not really written anywhere but that are, nevertheless, imposed by a certain powerful clique.

Connolley in Monte Carlo

Have you seen this cute video? (Via G.D.)

In the previous posting, we tried a couple of thought experiments. One of them was to imagine that the "global temperature" behaves like Brownian motion (which is approximately as good an approximation as the "random noise" around a "long-term average" in which the years are independent - because the long-term persistence in the real world exceeds that of the random noise but is lower than for Brownian motion).

By the term "Brownian motion", I always meant a random walk that generates a binomial distribution. Sorry for my sloppy terminology.

In our simple toy model, the annual temperature jumps, compared to the previous year, by +dT with probability 50 percent, and decreases by -dT with the same probability. What is the probability that all 7 years 1999-2005 will see a strictly lower temperature than 1998?

William Connolley uses the same technique he uses for the "real" climate - namely Monte Carlo simulations. He wrote the following comment:

• ... My calculation (by monte-carlo; I guess I should be able to do it exactly but I've forgotten how to if I ever knew) is that the chances are about 1/4 for equal up-down increments ...

OK, what is the correct result? Let us call the temperature in 1998 "zero" and let us choose units in which "dT=1". In 1999, "T=+1" with probability 50%. Only if it is "T=-1", we will have a chance for 7 cooler years, and it occurs with probability 50%. That's what's left in 1999. We will only consider the case "T=-1" because in the rest of cases, we have already violated our goal.

In 2000, the temperature will be either "T=0" or "T=-2". Both of them have probability 50% which means 25% of the total. We will talk about the (smaller) percentages of the total from now on. My original problem was defined so that "T=0" again (matching the record) already violates the conditions. So only 25% of cases, in which "T=-2" in 2000, will work.

Now you can already see that the final result will be below 1/4.

In 2001, it will be either "T=-1" with probability 1/8, or "T=-3" with probability 1/8, too. Both of them work.

In 2002, it will be "T=0" with probability 1/16 - which means a violation, or "T=-2" with probability 1/8 (combining twice 1/16), or "T=-4" with probability 1/16. Clearly, only the latter two cases with a total probability 3/16 survive.

In 2003, we will have "T=-1" with probability 1/16, "T=-3" with probability 3/32, or "T=-5" with probability 1/32. The total probability remains 3/16.

In 2004, the temperature will be "T=0" with probability 1/32, which means a failure, or "T=-2" or less with overall probability

• (3/16-1/32) = 5/32

If the temperature in 2004 is "T=-2" or less, then it will be below zero in 2005, too, and we're all set. Once again, the total result is that assuming the Brownian motion uniform-step model, the probability that we get 7 cooler years, after any specific year (that we called 1998), equals 5/32.

What about the Monte Carlo models? Our senior computer modeller told us that the right answer is

• 1/4 = 8/32

This is 60 percent above the correct result 5/32 (of course, the correct answer is what is taken to be 100%). Imagine that. A simple mathematical task involving one integer variable and seven mathematical operations "+1" or "-1" - a task that most of you could have solved analytically in the kindergarden. Even if neither you nor your nurse had known "probabilities", you could have listed those 128 equally likely histories (sequences of simple integers) and count how many of them satisfy the criterion. (A reader in the fast comment obtained this idea independently. A programmer could also use a computer to calculate the precise result by listing all 128 histories.) William Connolley had to use a computer with a Monte Carlo program (for William: programme), and he overshoots the correct result by 60 percent anyway.

What probability would you guess after half a minute of thought? 1/6? You would be 10 times closer to the truth than William Connolley with his "scientific approach" involving computers. Or 1/8, by phrasing the question so that the warmest year among eight in a more or less random sequence is the first one? You would still be 2.5 times closer to the truth than William.

Now imagine that you replace this funny model where we add 1+1 seven times in a row by a semi-realistic model of the climate that has billions of variables, thousands of physical effects (many of them hypothetical and many more probably missing) and hundreds of their mutual relations and feedbacks. These mechanisms involve many non-trivial cancellations that make the individual terms more important than in our case (so that a 60% error of anything is a disaster). You also improve the time resolution by three orders of magnitude, extend the predictions from 7 years to 50 years. Finally you give the new problem to William Connolley or his friends. What can you expect from their results if they're not even able to calculate 5/32 correctly? What you get is complete chaos, of course. Worthless numbers. Junk. Global warming. Methodological rubbish, using the words of Hans von Storch.

I suspect that they run their unrealistic computer games - that overshoot the global temperature anyway because they assume, among other things, that ice melts 1,000 times faster than it does - approximately three times, completely without any understanding, intuition or clue what's going on in the "black box", and if the third result is sufficiently politically correct and predicts a sufficient global warming to satisfy their brothers and sisters in the "scientific consensus", they promote the result into a scientific conclusion and their friends in the scientific journals happily publish this new kind of "science". This is what our society pays billions of dollars for.

Biased Brownian motion

We also mentioned the asymmetric case that William Connolley has surprisingly calculated pretty well - he obtained 1/10 while the correct result is 13/128. Imagine that the temperature increases by +1.5 with probability 50%, and decreases by -1.0 (centikelvin - but the choice of unit does not matter, of course) with probability 50%. What is the probability that 7 years after 1998 will be cooler? We already know the method, so let's list the percentages:

• 1999: T=-1 (50%), otherwise T non-negative
• 2000: T=-2 (25%), otherwise T non-negative
• 2001: T=-3 (12.5%), T=-0.5 (12.5%), otherwise T non-negative
• 2002: T=-4 (1/16), T=-1.5 (1/8), otherwise T non-negative
• 2003: T=-5 (1/32), T=-2.5 (3/32), otherwise T non-negative
• 2004: T=-6 (1/64), T=-3.5 (1/16), T=-1 (3/64), otherwise T non-negative
• 2005: T=-7 (1/128), T=-4.5 (5/128), T=-2 (7/128), otherwise T non-negative

The total of the surviving probabilities is 13/128 which is indeed close to 1/10. Once again, assuming Brownian motion with the up/down steps in the ratio 1.5 vs. 1, there is only 10% probability that after a year like 1998, all seven following years will be cooler.

You should not be shocked that the number 10% is so small. The same conclusion applies to other years, not just 1998, and for most others, the criterion is satisfied and they are not followed by a period of 7 cooler years. Everything morally agrees with the rules of chance, of course. In the short term, you can't really see any problems with the Brownian motion model, except that it is probably better than the "independent years" model.

William obtained a pretty good numerical result for the second task - and you may ask whether it is good news or bad news. It could be good news because he can calculate at least something. Let me offer you an alternative explanation. It is a bad news because it shows that he may have had the correct program but he does not know how to use it. More precisely, he does not understand that he must repeat the simulation a sufficient number of times for the average of his results to be close to the actual results. And he should actually try to figure out what is the variance of the results generated by the Monte Carlo methods, as long as we want to call it repeatable science.

William's large numerical error is kind of baffling because one second of computer time should be enough to find the correct results with the accuracy of several digits. Do the math. Repeat the simple history "N" times (less than a microsecond in this case!), and the relative error should go down like "1/sqrt(N)". You should get 3 valid digits within 1 second (million of microseconds).

This seems to confirm the hypothesis that no one has yet told them that they should estimate the error margin of their climate predictions. It really seems that they imagine that "Monte Carlo" programs should behave just like the casinos in Monte Carlo. Try your good luck five times, and when you're lucky and you win $100,000 or +8 Celsius degrees of warming per century, go home, turn your computer off, and celebrate! (And publish it, too.)

The CPU time could have been too expensive for William to reduce the error below 60%. But one can then ask How many times did they actually run the "real" climate models that have a million times as many variables and many thousand times as finer time resolution? Once? Or twice, choosing the "better" answer? And this single run not only predicts the future but also simultaneously validates the thousands of assumptions and parameters in the model, does not it? Because the calculation leads to the Big Crunch singularity of global warming and moreover also shows the warming in the present era, then the hundreds of assumptions must be correct, right?

Meanwhile, in India, as of today, the recent extreme record cold has killed 200 people. If you help to pay the money to Kyoto+ protocols designed to cool the planet, you may help to double such numbers. You will also help to further improve the snow record in Japan.

2005: second or third warmest year

Do you remember 1998? Was it a special year? Even though Al Gore was a vice-president, 1998 is still the "globally" warmest year on record.

Since that time, Bush was elected twice. The U.S. economy grew by 25 percent or so. The oil companies have been doing their best to produce as much carbon dioxide as they can.

But it does not work. No one can defeat Al Gore's 1998. It is not even clear whether 2005 was the second warmest year on record. It could be the third year after 2002.

• 2005 ties for 2nd warmest year

As we discussed many times, the dependence of the annual average temperature on the year behaves as something in between

• a random fluctuation from the temperature that you may want to call the "long-term average" in which the different years are independent
  
• and the Brownian motion where the temperature of the previous year is the starting point for the new one, and the step is random
  

This fact is what you can derive from the exponent in the autocorrelation scaling laws that is between the values that you would expect for these two idealized cases. You can easily see that neither of the idealized extreme descriptions can be correct because the first one essentially allows the temperature to be discontinuous while the latter one allows the temperature to drift away arbitrarily far - as sqrt(t) - in a time interval t which seems rather unrealistic for extremely long time scales.

People usually think about the first approximation as a better description. Every year is independent, they think, and every year fluctuates around some "fundamental" value "T_{Gaia}", and therefore it is shocking that the last 5 years were among the 6 hottest years during the period of the last 27 years, they think.

But in reality, 2004 was the starting point for the temperatures in 2005. You just can't change the temperature abruptly. It is all but guaranteed that the years with similar temperatures will be found in clusters. There is always some inertia, and the amount of inertia (or "persistence") at all possible time scales should be studied scientifically and without prejudices. Let me now take the second approximation, the Brownian motion, as my starting point.

From this Brownian viewpoint, it is shocking that the Earth was not able to improve the record temperature for 7 years. Try to do the calculation. Assume that every year, the temperature either goes up by +dT, or goes down by -dT. Take a year in which you achieved the maximum temperature and call it 1998. What is the probability that the Brownian motion will give you all seven years 1999-2005 to be strictly cooler than 1998? Be sure that even if the Brownian motion is unbiased, you will get a number that is much much smaller than 50%.

And now imagine that the global warming guys argue that the Brownian motion should even be biased towards the increasing temperatures. Try to do your calculation with the assumption that every year, the temperature either increases by 0.015 degrees or decreases by 0.01 degrees. You will find out that the probability that you won't defeat the warmest year for 7 years is tiny.

Nevertheless, it is exactly what we observe. Of course, we can make smart comments about this observation. 1998 was the warmest year because of the El Nino of the century - and we had no El Nino in 2005. But the global warming evangelists whose goals are purely political should think twice before they make such arguments. The more often they make these arguments, the more clear it is that the climate is actually dictated by natural factors, not the anthropogenic ones.

The data simply don't support the global warming speculations too well. Despite Al Gore's vice-presidency, 1998 was certainly not a disastrously hot year. And the planet was cooler for 7 years that followed. Does not this fact itself mean that there is obviously no observable threat to talk about?

Gross & Randall - never give up

As most of you know, my interpretation of various texts about the anthropic principle is not far from this one.

In the article Outrageous fortune, Nature argues that the anthropic principle is becoming a dominant view in the cosmogical and stringy circles. I don't think that this statement is true, and explicit polls demonstrate that the anthropic principle is rejected by the majority. But of course having a majority is not the important question for science itself. In science, it is enough if there is one researcher who happens to be correct.

In the Nature article, only Lisa Randall and David Gross argue that we do not have good reasons to accept the anthropic principle as a fact. Congratulations to David and Lisa. ;-) Juan Maldacena argues that the anthropic principle is the best thing we have today, but he hopes that it will be replaced by something better in the future. And several "usual suspects" :-) among our colleagues advocate the idea.

Lisa says the such a dramatic change of the methods in physics is premature and we should better look at the alternatives before we decide to "switch". David Gross says:

• People in string theory are very frustrated, as am I, by our inability to be more predictive after all these years. But that’s no excuse for using such bizarre science. It is a dangerous business.

I think that this is a very fair description. Even if things are more difficult than we would like to, it is still a good idea to remain rational and preserve some basic scientific and moral principles. This discussion reminds me of the debates about the newly-born Christians we had with my ex-GF in the college who was a strongly believing person and who was, of course, attempting to convert me, too.

The usual story was as follows: there has been a gangster or a drug addict, or someone who had some terrible problems, and so forth - and eventually he or she decided to get converted to Christianity and believe that the Bible was literally true. Well, these examples did not work for me. "I will never be SO frustrated to abandon the very rules of honest thinking" was what I always thought. ;-)

I think that some temporary - and even less temporary - problems cannot be a good reason to abandon certain principles or to become corrupt. That may be the end of the good story. Some things don't work as much as you would like? OK, but that's still a very different issue from accepting an attitude that is morally problematic or scientifically flawed. Do you feel more vulnerable to various external pressures just because something else in your life does not work as well as you would like? Think twice.

It is quite clear that we would never think about accepting a viewpoint that is as intellectually weak and as non-quantitative as the anthropic explanation of the fundamental properties of the real world if the progress in science were as fast as it used to be in the happiest periods of science. Do you think that the progress is not so fast these days? OK, maybe, but any kind of dissatisfaction of this sort is insufficient to accept ideas that have no quantitative scientific justification.

You should better live with the fact that the pace of our learning is slower these days, and that eight years of our failure to understand the smallness but finiteness of the cosmological constant does not prove anything. OK, maybe we need nine years. But once we promote our ignorance to a new physical law - a law that says that things must be what they are and we should not ask WHY - then we will need centuries to get back on the track.

We must always keep on asking WHY because this is the most important question there is. We have inherited some ideas that are unnecessary. We have to jettison this excess baggage in order to make progress. (Murray Gell-Mann in an Enron commercial.)

And the answers to very different WHY questions must be different. If the answers to ALL of our WHY question are the same - for example "Wakalixes" or "God" or "We would not be here otherwise", then you can be sure that we're no longer doing science.

Ghost D-branes

Tadashi and Takuya have an interesting proposal to interpret the "fermionic" Chan-Paton factors - those that extend a gauge group from U(N) to a supergroup U(N/M) - as creating "ghost D-branes". All their states violate the spin-statistics relation. Note that the cancellation between these two D-branes may be viewed as perfect in topological string theory but Tadashi and Takuya talk about the full string theory.

When a D-brane coincides with a ghost D-brane, the configuration is equivalent to the closed string vacuum. However, when they are separated, they get a new configuration. Using these rules, I am a bit surprised that you can separate them. If the coincident D-brane and ghost D-brane contain no physical open string excitations, does not it mean that we should not be allowed to give one of them a vev?

They also discuss the heterotic dual. In this case, they extend the fermionic formulation by adding new chiral bosons to the 32 fermions.

Bayesian probability II

See also a positive article about Bayesian inference...

Our fellow physics blogger Steve Luttrell believes the anthropic principle. That's not terribly unusual - roughly 20 percent of the physicists believe the same thing. But he even claims that the weak anthropic principle is science while insisting that the physics predictions should be derived from the first principles is philosophy. I am not kidding - see the end of this article.



The search for the first principles and insisting that we have a well-defined set of rules of the game that should be tested is what has defined natural science at least since the era of Galileo Galilei. I understand if someone is only interested in approximate laws that describe a certain class of phenomena. I understand that many people study so complex systems that they are forced to change their ideas about the system very frequently. I can even marginally understand if someone allows herself to "generalize" science in such a way that even the first principles are vague or environmental. But claiming that the standard rules of science - such as the assumption that there are some rules or first principles at all - are philosophy - it looks like a new level of madness to me; I apologize for this word. In some corners, the anthropic madness is evolving really quickly.

More recently, Steve Luttrell also advocated the Bayesian probability, something that we discussed recently. Frankly speaking, with all my respect to Steve Luttrell, I don't see a single argument about the essence of the question itself on Steve's page - just a lot of fog that "this is beyond my field of expertise" and all this ad hominem nonsense. So let me discuss this question at a comparable level of social science, too, because unfortunately there is no science to reply to, as far as I see.

Well, I exaggerate. I will increase the amount of essence in these comments at least by one order of magnitude compared to Steve Luttrell.

It is often said that there are two basic interpretations of probability: frequency probability (the ratio of events in a repeated experiment) and Bayesian probability (the amount of belief that a statement is correct). I am, much like an overwhelming majority of physicists, statisticians, and probability theorists (see the Wikipage about the frequency probability to verify my statement) convinced that it is only the frequency probability that has a well-defined quantitative meaning that can be studied by conventional scientific methods.

This is why Luttrell's attempts to paint my opinions as fringe opinions are completely crazy.

The Bayesian probability cannot be even defined without vague words like "belief", "plausibility", and so forth. It's just not a well-defined quantitative concept because it cannot be determined or measured with ever higher degree of accuracy. Such a kind of probability is not predicted by meaningful physical theories of physics either. The predictions of quantum mechanics are always about the frequentist probabilities. I often give numbers for "subjective probabilities", but I would never argue that such estimates are scientific. They're not scientific much like other beliefs are not scientific. Counting the angels is not scientific either.

If I say that the U.S. president is a distant relative of a particular governor with probability 20%, that's a scientifically meaningless statement with a meaningless number. The correct answer is, of course, either 0% or 100%, and the precise value 20% only reflects my psychological feelings and irrelevant subjective methods that I used to estimate the degree of "plausibility" of that statement. It's not objective, it's not measurable, it's not science. Other people can tell you a different estimate (70%) and there is no way to decide scientifically whose number is correct. If the ongoing research of this question becomes advanced enough, it may turn out that both of us were wrong, of course, because the answer is either 0% or 100%. No intermediate value can be thought of as "permanent truth". Someone may have been closer to the truth; but no one was right.

These statements about the nature of probability are completely essential for a physicist, a statistician, or a probability theorist to do her work because probabilities appear everywhere. According to quantum mechanics, everything we can predict are probabilities. I can't imagine how a physicist could study her subject if the meaning of the word "probability" were beyond her field of expertise.

What Steve Luttrell's description reminds me are the postmodern, lit crit misinterpretations of the meaning of science. They say: You know, science is just another religious ritual. The way how we do science is flexible. The natural laws are like a sneak, and we are re-adjusting them by interacting with the real world. There is no objective truth. All statements in science are just a result of social influences, discrimination and political power, including the value of PI. ;-) ... I don't need to repeat all this rubbish, you can read it in Alan Sokal's paper and all other, less perfect papers that promote the very same nonsense with a serious expression in their face. ;-)

This is not how this Universe works. The laws of Nature are like very rigid stones that are placed on other stones. Our environment is changing but the laws of Nature have always been the same. And we are learning these eternal laws with ever increasing accuracy and completeness. The more we understand how the laws of Nature work, the more they look like a hierarchy of stones placed on other stones. The less we understand them, the more they look like a shaky, flexible and sleeky snake that changes every time we try to touch it.

Robust vs. liquid science

It's pure and simple. Those who understand science prefer a quantitative, frequency-based interpretation of the probability, the existence of first principles whose validity should be tested by experiments, and other rigid scientific rules to search for the truth. Those who misunderstand and dislike science, prefer to "measure" the probability by the amount of beliefs and think about the laws of Nature as about an evolving sleeky snake.

The last category will never tell you what is exactly their prediction. They will never tell you whether their "global warming" predicts increasing or decreasing mass of ice in Antarctica. They will just try to derive a political capital from whatever answer they can get. They don't believe that there is anything such as the truth. They only believe in their personal interests. (I must sound like Ehud Barak when he explains that Arafat - and maybe most of Arabs - did not know the concept of the truth; the detector of lies would not work there.)

Positive words on Bayesian probability

While I say that the Bayesian probability is not science, it can be useful for various purposes. We may use it as a key to figure out how to behave when we don't know something - how to act in the state of ignorance. Search engines use the Bayesian formulae to organize their databases and sort the web pages. But what I want to mention is something different:

Quantitative Occam's razor

This observation makes the situation a bit more complicated because Steve Luttrell believes both Bayesian probability as well as the anthropic principle with its Rube Goldberg machines. However, the Bayesian probability offers tools to justify - and indeed, quantify - Occam's razor, a gadget to kill the anthropic principle. Simpler theories are more likely to be true.

What do I mean? A model with many parameters is almost guaranteed to fit the data better than a model with a few parameters. Which of them is more likely to be true? The Bayesian probability paradigms imply that it is the simpler model, even if its predictions are a little bit less accurate than the predictions of the model with many parameters. It is because the prior probability that a complicated model - before its parameters are determined - predicts particular results is small exactly because the probability distribution is smeared over the whole parameter space of the possible results.

I can't tell you exactly what the distribution is because the Bayesian probability is not quite quantitative. But it is enough to demonstrate a qualitative point.

The prior probability distribution for a simpler model is more concentrated. The Bayesian "level of confidence" formulae tell us to include the factor that "punishes" the model for being complicated. If you do the calculation in the Bayesian way, I believe that you will conclude that it is exactly as reasonable to believe that a model with 10^{120} vacua predicts the correct cosmological constant after one vacuum is selected (anthropically), as it is to assume that one particular single-vacuum model will miraculously give the right cosmological constant with the relative accuracy of 10^{-120}. In both cases, the psychological probability that the model is correct will be 10^{-120}. This is how the Bayesian probability works, and I fully endorse this particular conclusion.

Note that when we also consider the probability that the models predict the correct Standard Model, not just the cosmological constant, a particular heterotic model will become more likely than the whole landscape of type IIB flux vacua. This is again what the Bayesian reasoning implies. The anthropic people will deny this conclusion - except for Steve Luttrell who will struggle in between two contradictory ideas.

However, my inability to convince everyone else that the huge landscape does not make the cosmological constant more "Bayesian-probable" or "believable" or "reasonable" is evidence that the Bayesian probability is not really science. It is philosophy. And while I would agree with some of its intuitive conclusions, it's just not possible to argue that these conclusions are scientific. If we don't know how the vacuum selection really works in the world around us, we cannot calculate meaningful "probabilities" that one answer is correct. Maybe if I pretended that the Bayesian probability is science, I could convince a few hundred people that any vacuum from a large set is unlikely...

Memorial service: R. Bott

There will be a memorial service for Raoul Bott on Sunday, January 29 at 1:30pm in the Memorial Church on Harvard campus. A reception will follow.

Witten's dog

It turned out that Witten's dog, the simple perturbative diagram in superdupersymmetric string theory, is actually dual to Schrödinger's cat. Did you know?

A young string theorist in Oregon

I received an e-mail from a colleague of ours in Oregon that is pretty cute. ;-)

dear Mr Motl

My name is [A. K.]. I am in grade 4 [10 years] and live in Oregon. My teacher said in class something on particles we are made of. I asked her more about particles but she did not say more.

I used google to search for more on particles and saw strings as what particles are made of. I used google to look for more on strings which showed a book by Brian Green and Micho Kaku. I got my dad to get me the Green and Kaku books. The Green book is harder to read. The Kaku book is easier. I find neat is how the world is made up of particle and small strings. I ask my dad and mom for more on strings. They did not know much.

I want to know more on strings. Some string web pages look like math I dont know. I want to do strings with math. The Green Kaku books do not have the math I saw on some string web pages. My dad says the math is algebar and calculus. He got me the books algebra for dummies and calculus for dummies. In some pages I can get answers from moving symbols around. I do not know why I get the right answers. I do not see how the math is done in strings. There is alot Kaku and Green do not say?

I used google to find more on strings and saw your name on lots of web pages on strings. I want to do strings when I am older. How do I go and do strings? What do I have to do? Do people do strings for a job?

School is very boring and easy. Particles and strings look exciting and neat to me. I want to learn more. I have nothing to do outside school. What did you do to learn strings?

[A.]

Pure quantum gravity cannot work

One of the simple - although not quite new - consequences of the "swampland" line of reasoning is that pure theories of quantum gravity cannot work.

This conclusion that we will justify below applies to various loop quantum gravities, spin foams, causal and acausal, dynamical and non-dynamical triangulations, tetrahedronizations, and any other misinterpretations of quantum gravity that you have heard of.

Quantum gravity cannot be studied separately from the other forces, and the other forces cannot be thought of as small corrections to quantum gravity.

On the contrary. In every consistent theory (and background) of quantum gravity,

• gravity must be the weakest force (much like in the real world)

in the sense that there must exist particles charged under any other kind of force for which the force of gravity is subdominant; their mass/charge ratio is smaller than for extremal black holes and the overall force between two copies of such a particle must be repulsive. This statement may be (and has been) justified by many arguments, for example:

• the entropy bounds and the absence of remnants
• the ability of extremal black holes to decay unless they are BPS
• the continuous character of the magnetic monopole charge of all objects that can be described as black holes
• the verification that the rule is satisfied in all classes of string theory backgrounds that have been looked at

According to our knowledge of string theory, it seems that there also cannot exist any backgrounds which only contain massless gravity but no massless gauge fields or scalars. See page 6 of the Swampland paper, for example. Pure quantum gravity does not seem to be an option. Moreover, we know that in the real world around us, gravity is not the only force - and the strength of the other forces does not go to zero, not even at the Planck scale.

Let us accept that pure gravity is not the final goal. Can it be a step towards getting a full theory, after we "add" the other forces such as electromagnetism as perturbations?

The answer is a resounding No.

When you add a force that you want to treat perturbatively, which should be possible if the success of QED is reproduced by your quantum theory of gravity and electromagnetism, then you are expanding around "g=0" where "g" is the gauge coupling. In quantum gravity, there is a new ultraviolet cutoff "g.M_{Planck}" above which the effective theory breaks down. If "g" goes to zero, then this scale goes to zero, too. The theory therefore breaks down at all scales. You can't expand around the point where gravity is the strongest force because a quantum theory of gravity in which gravity is stronger than other forces is inconsistent.

In unified theories - i.e. in string theory - this problem is avoided because the same coupling "g" also governs the strength of gravity, and setting "g=0" implies that "M_{Planck}" goes to infinity and the cutoff scale remains finite.

Well, I don't expect that the people who try to study "pure quantum gravity" will suddenly realize and accept these observations. But I do hope that many other readers will get the point. When the role of quantum mechanics is considered, other forces cannot be neglected when we try to include gravity. All forces must be studied simultaneously which is why a unified theory is necessary for a description of quantum gravity to be consistent.

This is the 17th known reason why string theory is the only tool to study quantum gravity, beyond the semiclassical approximation, that we have as of January 2006.

Energizing the quest for a TOE

BBC describes the LHC - and they help to energize the quest for a "big theory". ;-)

Dangerous ideas

Last year, the annual question of edge.org was

• What do you believe but you can't prove it? (2005)

This year, John Brockman et al. ask what is your

• dangerous idea? (2006)

Let me choose some of the famous personalities whom I find interesting.

Steve Pinker knows what to say

Steve Pinker's dangerous idea - one that will spread in the next decade - is that different groups of people genetically differ in their talents and temperaments. He disputes the claims that the races do not exist, and so forth, and thinks about the potential impact of these insights. He argues that the differences between the two sexes are rather well-established and the differences between the races less so. Of course, I would probably subscribe to almost every single word he wrote.

Also, we may worry about various violent political implications of these insights. These threats do not worry me too much because I have spent one half of my life so far in a system whose generalized form has killed more people, using the ideas of equality, than the Nazis killed using their racist hypotheses. I just don't think that science directly determines politics or even kills the people. I don't think that the truth may be "evil". And I certainly don't think that the moderates and right-wingers are more evil than the left-wing radicals. ;-) It's always the people themselves who kill (or discriminate against) others - and science itself can very rarely justify an extremist political viewpoint.

Needless to say, some people find Pinker's simple comments truly dangerous - and our pinko feminist friends over at Cosmic Variance get really furious about them. ;-) Sean Carroll argues that Steve Pinker is either an idiot who does not understand the difference between suggesting a hypothesis and using the hypothesis to explain the data (Sean has probably lost his mind completely: explaining the data is the very purpose of all hypotheses), or that Pinker is "lying intentionally to score some points of his own". Well, Sean Carroll may be used as an example that the people can behave like wild animals in the name of "equality" much like they can behave so in the name of "differences".

Sean also asks how loudly does he have to shout for his misconceptions to be generally accepted. The answer is that no volume is sufficient to achieve this goal in the U.S.; 90 decibels is however enough to be identified as mentally ill and 180 decibels is enough to be used as a motor for Boeing aircrafts. In the feminist update of the North Korean regime, 5 decibels is enough to codify your ideas assuming that you are a prominent member of the leading party. :-)

Some of the other ideas I completely agree with: Irene Pepperberg argued that the differ