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.
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.
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.
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
Four democrats supported Samuel Alito and one Republican opposed him. Congratulations to the 110th justice.
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.
The event's website contains basic data about the conference. Let me exceptionally behave as a linker-not-thinker.
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...
V. Gates, M. Roachcock, E. Kangaroo, and W.C. Gall from the Institute for Really Advanced Study (IRAS) established a new
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.
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:
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.
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.
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.
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:
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.
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.
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. :-)
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)
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.
David Goss has pointed out a press release about
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
and an article in the new issue of Physical Review Letters. The homepages of the projects are here:
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:
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.
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
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.
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.
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.
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.
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.
by Robert C. Helling (firstname.lastname@example.org), 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.
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. ;-)
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.
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.
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.
As Alex W. has pointed out to me, PhysOrg.com informs about the work of
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.
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.
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.
- 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.
- 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.
- These are based on quantization of a set of classical field theories which are constrained topological field theories.
- 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.
- 2) there is a common mathematical and conceptual language and some calculational tools which are useful to study such models and
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.
- 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.
- 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).
- It is unfortunate that they omit reference to such key results which resolve issues they mention.
- 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.
- 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.).
- 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.
- 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.
- The freedom to specify spin foam amplitudes does not map onto the freedom to specify parameters of a perturbatively non-renormalizable theory.
- 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.
- 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.
- 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,
- 2) whether thus there are any links between the spin foam amplitudes and Hamiltonian evolution,
- 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).
- I don’t agree with all the details of their discussion of these issues, but these certainly are open issues.
- 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.
- 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.
- This does not prevent us from writing down and deriving predictions from heuristic semiclassical states (hep-th/0501091),
- or from constructing reduced models to describe black holes or cosmologies and likewise deriving predictions (astro-ph/0411124),
- 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).
- 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?
- 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.
- In addition it must be stressed that there can in physics be generic consequences of classes of theories, leading to experimental predictions.
- Here are some historical examples: light bending, weak vector bosons, confinement, principle of inertia, existence of black holes.
- 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.
- LQG predicts a number of such generic features: discreteness of quantum geometry,
- horizon entropy,
- removal of all spacelike singularities,
- and I believe will soon predict more including DSR, emergence of matter degrees of freedom.
- 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.
- Since we know the theory is uv finite this does not affect existence.
- The lack of a uv unique theory does not prevent us from testing predictions of QFT in detail,
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.
- 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.
- 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.
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...
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.
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.
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.
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.
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.
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. :-)
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.
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.
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.
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.
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).
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.
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
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.
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.
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.