Sunday, November 28, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Bush's space program

Let me make the main message of this article clear at the very beginning:

  • In January 2004, I was impressed by Bush's speech about the long-term goals of the space exploration program.
Risa - an astrophysicist from Chicago - just posted an article about this topic on Sean Carroll's blog:

http://preposterousuniverse.blogspot.com/ ...

The Congress has approved the higher funding for NASA

http://www.nytimes.com/ ... /24nasa.html

which is viewed as support for Bush's visions.

I have read the complaints of the American Physical Society, and it was a less pleasant reading for me. These texts

http://www.aps.org/ ... (press release)
http://www.aps.org/ ... (report)

mostly sound like demotivating statements of bureaucrats - no doubt, in reality, there is a lot of outstanding scientists among them - who are always ready to kill every specific idea and replace it with a lot of neutrally sounding, boring cliches. They say, among other things
  • The plan is extraordinarily difficult.
  • It could threaten the funding of some other existing projects KQ, UH, PT, SJ.
Some sentences are so artificial, long, and boring that I don't even want to reproduce them here.

Concerning the second point above: it is exactly the whole point of the new vision of Bush - and any other vision of a similar kind - to re-evaluate the ideas what is important and attractive about the space exploration program and which projects should be completed and canceled. Some scientists just to believe that once their research of something has been accepted as legitimate research, it must be funded forever - and they would even like to hear that it is important forever. This is not how science within a finite society can work in the long run.

In fact, I would find it very useful if an influential politician who still knows how to be excited by something - like Bush - looked at other fields in science including particle physics. I think that the particle physicists - namely the experimentalists - are not using their resources efficiently either, and they're continuing to do many things that are almost guaranteed to lead nowhere, even though one could find many other projects that may have very clear and totally amazing outcomes. How much do we believe that Tevatron will bring us anything new and important? Of course that the world must preserve its family of skillful experimentalists even during the times in which the progress in the experiments is nearly frozen; but even such conservation should be done efficiently, and with a clear idea about the long-term goals.

Although I am a very theoretically oriented person, it's clear that I don't really care about KQ, UH, PT too much - and I care about SJ just a little bit. A human mission to Mars is something on a completely different level. Of course that such a mission is not just a matter of pure science. It is a way to realize the dreams of many of us - scientists as well as other people - dreams that we have had since we were little boys and girls.

A human mission to the Moon - or even to Mars - is something amazing and irresistable. And the idea of a more permanent base on the Moon or on Mars would represent new steps towards the dreams about a big future of our civilization. People were able to fly to the Moon in the 1960s and early 1970s, but it seems much more difficult for us today. What happened with us?

Let's list a few numbers:
  • The International Space Station's (ISS) total cost has been about 100 billion US dollars
  • The canceled Superconducting Supercollider (SSC) would only cost 8 billion dollars
  • The total budget for various telescopes etc. between 2000 and 2010 is about 5 billion dollars
  • The total cost of the Large Hadron Collider (LHC) is about 1.5 billion dollars
These basic numbers describing different projects should be listed for many other projects in science and space exploration, and there should exist a reasonable discussion within the scientific community and the policymakers which of these things are good investments and which of them are less good investments.

I may be a biased particle physicist, but the fact that we could have built 12 SSC supercolliders instead of the ISS is shocking. I have almost no idea what the ISS has been really good for - in what sense it was "better" or "more exciting" or "more scientifically interesting" compared to the first flight of Yuri Gagarin, for example. Note that it's nearly as expensive as the war in Iraq.

On the other hand, humans on Mars would be inspiring for the whole humankind.

Many people are scared by the dim future of the Hubble Space Telescope. You know, the funding in 2009 should be moved to the James Webb Space Telescope - a telescope that will focus on the infrared spectrum. My guess is that the Hubble will be viewed as giving us "nothing really new" much before 2009. Once it retires, it can be privatized or given to another country, and so forth. The progress must simply go on, and it is a completely wrong approach to assume that we will continue to work with the same technology forever. Of course that there must be completely new projects and new machines. And if there is a clear direction, it motivates the people to work on their specific tasks. And finally, it also encourages progress in the industry.

And let me make it sure that there exists no physical principle that will prevent the people from visiting Mars.

The report of the APS also says that the humans on Mars would also be counterproductive because they would contaminate the environment and prevent us from investigating the primary question - namely whether there has been life on Mars. I find such arguments ludicrous, and it's bad if such arguments are used to inhibit the progress in the space exploration program.

First of all, the humans could only "contaminate" the environment by the usual, terrestrial forms of life - and if such forms are found on Mars, everyone will believe that they were brought from the Earth anyway. If other forms of life - like different patterns replacing RNA/DNA - are seen on Mars, then the contamination by the terrestrial forms of life means no problems. Finally, if there's been any life on Mars, it does not seem that it could have been too impressive. I just think that Bush's vision of future life on Mars - something that we can initiate - is a much more exciting idea.

The possibility that there will be a usable base on Mars in this century is 100 times more intriguing than some hypothetical speculations that a robotic probe could find some specific organic compound on this planet. If we were able to create more permanent bases on the Moon or on Mars, it would give us new tools to investigate the Universe, and new hopes to expand our civilization to other places in the Cosmos.

Saturday, November 27, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Violation of complementarity?

It's kind of surprising that no one in the high-energy community has discussed this amusing experiment by Shahriar S. Afshar.

Afshar page
Afshar PDF
Questions welcome (Afshar's blog)



I learned about this experiment from Wikipedia where it was uncritically described at various pages about the interpretation of quantum mechanics.

This Gentleman and colleague of ours has argued that he was able to falsify the Copenhagen interpretation as well as the Many Worlds Interpretation - WOW - and confirm an obscure interpretation - the so-called Transactional interpretation by an interference experiment of the type Welcher Weg (which way). This transactional interpretation, proposed by a physicist John Cramer, is based on signals being sent back and forth in time. :-)

Incidentally, an older article about the interpretation of quantum mechanics on this blog is here:

Friday, November 26, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Lucie Vondráčková: Strach (Fear), English lyrics

Lucie Vondráčková: Strach

Czech lyrics

Category theory and physics

John Baez's "This Week's Finds in Mathematical Physics (Week 209)" is about one of John's favorite topics, namely category theory.

http://math.ucr.edu/home/baez/week209.html

Incidentally, the previous week 208 was discussed here.

You know, category theory is the most abstract and "universal" part of rigorous mathematics, and it is also known as the (generalized) abstract nonsense. Actually the supporters of category theory don't view this name as an insult but rather as a cool compliment. Many of us have had a period in which the mathematical rigor was almost irresistable.

Category theory involves various theorems about sets, categories, functors, homomorphisms, and other abstract objects. Instead of saying "we perform an analogous procedure with a different kind of theory", category theorists give you a framework that translates vague words such as "analogous" into a mathematically rigorous structure.

This approach is meant to unify all of mathematics and all of rational thinking. You would think that the result must be very deep and hard to understand. But the actual results and tools of category theory are often closer to ordinary diagrams (combinatorial graphs) with arrows in between the objects - similar diagrams like those used by the people from the commercial sector in their PowerPoint presentations.

The mathematically oriented part of the string theory community is mostly excited by category theory. The so-called "derived categories (of coherent sheaves)" have been proposed as a generalization of K-theory to describe D-branes of various dimensions. Unlike K-theory that only knows about the allowed conserved charges of D-branes in various backgrounds, category theory should also know - and perhaps knows - something about their dynamics, for example the points in the moduli space at which the D-branes become (un)stable or (un)bound.

Wednesday, November 24, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Ukraine and reunification of the West

The messy elections in Ukraine look pretty serious. Just to make the situation clear:

  • There were two main presidential candidates. Both of them are called Viktor, but at most one of them can be the victor at the very end.
  • Viktor Yanukovich is a pro-authoritative, pro-Russian candidate, supported by the Eastern half of Ukraine as well as by Lukashenko and Putin (Byelorussia and Russia). Let me call him Viktor East because you may be confused by the similar names.
  • Viktor Yushchenko is a pro-Western, center-right candidate, who enjoys the support of the Western half of Ukraine, as well as the European Union and the United States of America. Let's call him Viktor West.
  • Exit polls indicated that Viktor West would win. Exit polls are not that important. Nearly official results indicated that Viktor East has won. However, the international observers claim that the polls were flawed. A lot of concrete accusations were raised and the EU and the US require a detailed audit of the polls.

Countries such as Czechia, Slovakia, Poland, Hungary, and the Baltic states are already members of the EU. Bulgaria and Romania could join the EU in a couple of years. The Baltic states are the only countries of the former Soviet Union that left the Commonwealth of Independent States. However it is pretty unlikely that Russia will join the EU in the foreseeable future. A real open question is Ukraine. Russia wants to interpret Ukraine as a "friendly region abroad" which is of course not quite compatible with Ukraine marching to the West. It's not shocking that Ukraine is the natural battleground for any new tension between Russia and the West.

Tuesday, November 23, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Aliens' answer to the anthropic principle

Cumrun Vafa has just pointed out a new article in the Time magazine to me. The address is

http://www.time.com/ ...

The article starts by explaining who are cranks, and why many scientists turn on their e-mail filters to avoid all contacts with the crackpots. However, the article itself is then becoming increasingly entertaining, frustrating, or irritating, depending on your mood.

It explains that many parameters of the world seem to be adjusted in such a way that life is possible, and roughly speaking, the text proposes four main different explanations why it's so - and the first three explanations are related:

Sunday, November 21, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Cultures in theoretical physics

Amazon.com has included two popular books in their listings - both of them should appear on April 30th or May 1st, 2005 - about our field.

First of all, it is a very insightful and extremely useful book by Lisa Randall

Warped Passages : Unraveling the Mysteries of the Universe's Hidden Dimensions
by Lisa Randall

String theorist vs. SUVs

All of my left-wing anti-gasoline readers - and they probably constitute a majority of the readers - should consider their support for Billy Cottrell.

Billy Cottrell is a slightly eccentric :-) 23-year-old graduate student from Caltech who decided that the SUVs were evil, and therefore spray-painting (and possibly also torching) these SUVs is the right answer.

The total damages are about 2.3 million dollars and Cottrell has been threatened with up to 40 years in the prison. Well, it's not too surprising that he has probably agreed to become a police informant and his ecoterrorist friends have unfortunately stopped their support.

But why is it interesting? It's because Billy is described as a string theorist! The judge Gary Klausner, for example, mentioned that "string theory was an area of physics". Billy corrected him: "It's the area of physics." :-)

Of course, it's too bad that Billy has put himself into such problems, but he has some sympathies of mine, too. The main difference between Billy and the Kyoto protocol is that the damages made by Billy are 2.5 million, while those caused by the Kyoto protocol in the world will be 2.5 trillion - and the latter will be completely legal, unlike Billy's Molotov cocktails. :-) Moreover, the Kyoto is much less focused.

http://www.spiritoffreedom.org.uk/ ...
http://www.freebillycottrell.org/
http://www.pasadenastarnews.com/ ...
http://www.google.com/ ...

At any rate, I would like to discourage all of my other fellow string theorists from torching SUVs and other types of ecoterrorism.

The newest developments (I wrote them before, but blogger.com was frozen): Billy has been convicted on virtually all charges facing him, except for the most serious one that would imply at least 30 years in the prison. Without this particular charge, he is expected to spend roughly 5 years in the federal prison. His attorney wanted to argue that Billy had Asperger's syndrome, but it won't work, it seems.

I learned that he wrote a bachelor thesis about p-adic numbers in string theory at Chicago... I also learned about his research at Caltech which should be kept confidential, I think.

Saturday, November 20, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Ian Swanson and other talks

Because the behavior of Linux and Mozilla is mostly unpredictable, I will try to write shorter articles.

Ian Swanson from Caltech has been visiting us. He has told us a lot of interesting stuff, and was also giving a special seminar yesterday (Friday) at 3:00 pm.

He used PowerPoint with a lot of sophisticated equations, tables, and some animations. His topic was String integrability and the AdS/CFT correspondence.

Let's describe Ian's talk and the current status of the post-BMN business. Because I am writing this for the second time, let me be shorter:

  • the industry of the pp-wave limit has transmuted into the spin chains and integrable systems
  • Ian Swanson et al. (which includes John Schwarz, but also Jonathan Heckman who is now at Harvard) studied the physics of strings beyond the pp-wave - which means that AdS5 x S5 is described as the pp-wave deformed by some 1/R^2 corrections
  • the gauge theory side of the calculation more or less reduces to the spin chains and other tools of integrable systems
  • the string theoretical side is described by the Green-Schwarz string that, at least classically, becomes the supercoset SU(2,2|4) / ( SO(5) x SO(4,1) ), if I remember well - and as long as you forget about stringy loops, the ghosts (like Berkovits' pure spinors) are not necessary
  • the integrable structure on both sides agree, even though it is not manifest
  • most of the calculations are done at the leading order of the 1/N expansion (or the J^2/N expansion), and the stringy loop corrections are more or less open questions
  • the results are still expanded in lambda'=lambda/J^2, and in 1/J
  • the gauge theory (spin chains) agrees with the string (supercoset) at the one-loop and the two-loop level
  • there is a discrepancy at the three-loop level, and Ian says that it is believed that the problem is a subtlety neglected by the spin chain models
  • many states are combined into various multiplets, and there is indirect evidence of the existence of an infinite number of conserved charges that make up the integrable structure

Puppet show



The video above is from the future - from 2006 - but let us return to the present, 2004.

Friday, November 19, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Tom Banks at Harvard

Note added: this article has been updated, and two talks about two-dimensional string theory are briefly described at the bottom.

As Aaron Bergman and Jacques Distler pointed out, Google started another service:

http://scholar.google.com/

It is a fulltext search engine through all scientific articles, including all articles from www.arxiv.org (the PDF files are those that are linked), and it knows about the number of citations. The server lists the article with the given query and it prefers the cited articles.

For example, search for

Wednesday, November 17, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Orbifold tachyons from SUGRA and other papers

Last time when I commented all the articles, we were impressed how interesting and serious they were. Tonight it's slightly easier to describe all the hep-th papers on the web, but some of them still look interesting:

This paper by Matthew Headrick and Joris Raeymaekers is obviously interesting. Consider the nonsupersymmetric orbifold of type II string theory - Adams-Polchinski-Silverstein (APS) type of orbifold - on C/Z_n for large n. You know that there are many tachyons in the twisted sectors. For large n, it makes sense to T-dualize around the angular direction of C/Z_n. You get some SUGRA solution. Well, many people have definitely looked at the orbifold in this way, using T-duality. But Matt and Joris finally consider the obviously interesting limit in which n is sent to infinity, but you keep n times alpha' fixed. It's some kind of zero slope limit, but the "lightest" tachyons (=closest to being massless) whose squared masses are comparable to (-1/alpha' n) survive this limit because these squared masses are exactly inverse to the quantity that is kept fixed.

Note that the tachyons come from twisted sectors. By interpreting the angle as a circle, they're winding strings. It means that in the T-dual picture, they are momentum modes of a field in the dual string theory which is effectively supergravity. Finally, the present authors calculate some interactions of the momentum modes in supergravity - which exist off-shell - and they show that they agree with the couplings of the different tachyons calculated from the CFT - which only exist on-shell. That's very interesting. The main thing I worry about is that the result is perhaps not too unexpected because instead of the orbifold, one might work directly with the "limiting CFT" on the thin cone and its T-dual.

This author constructs some new solutions of the modified Ricci-flatness equations, something that is necessary for a CFT to be well-defined. You know that Ricci flatness is the right equation of motion only if you have no fluxes and if the dilaton is constant. If the dilaton is not constant, the Ricci tensor is nonzero - Einstein's equations get a source. He or she does not quite want to talk about a non-constant dilaton. Instead, he or she focuses on another generalization of the CFT and Ricci flatness - namely a CFT with an extra complex field that has an "anomalous dimension". My understanding is that it's just a matter of notation whether you say that a field has an "anomalous dimension", or whether you redefine it by a function of the dilaton, and you allow the dilaton to vary. If my understanding is correct, Nitta has effectively found new solutions of the combined Einstein's equations with some dilaton-gradient source. These solutions have either a U(N) isometry, or an O(N) isometry. It's because the coordinates of his or her manifolds are explicitly written using U(N) or O(N) covariant coordinates, and the metric only depends on the quadratic invariants. Some of these solutions can be interpreted as generalizations or deformations of the Ricci-flat metric of the conifold with an extra linear dilaton - at least that's my impression.

We often say that the maximally supersymmetric Yang-Mills theory in four dimensions is "finite" because of powerful supersymmetric cancellations. Well, what is exactly is finite? Clearly, there are operators with anomalous dimensions that must be regulated and that are cutoff-dependent, and so forth. So it's not everything that is finite. However, the effective action is something that should be finite - it sort of computes the correlators of the elementary fields in which the divergences are supposed to cancel between the bosons and fermions. In this paper, these two guys try to prove the finiteness of the N=4 effective action in the N=1 superspace language. The effective action of N=4 can be written in this form, due to the Slavnov-Taylor identity, as long as we allow the superfields to be "dressed". They must go through some un-controversial steps to show that the R-symmetry anomaly cancels due to the N=2 supersymmetry, and they re-check that the one-loop beta-function vanishes. Nevertheless, the final result is that once you express the effective action of the N=4 gauge theory in terms of the dressed fields, all the terms become independent of the UV cutoff, and the effective theory is therefore finite.

OK, there was a Lorentz violating paper last time, too, and many comments may be repeated. I still don't understand the motivation behind these models. The space of possible non-relativistic non-stringy quantum field theories is huge. I don't really feel what constrains it. For relativistic theories, we may label all fields by their dimension - which is their dimension with respect to space as well as time. However, for non-relativistic theories, we must introduce separate spatial and temporal dimensional analyses, and I don't think that we can really distinguish "renormalizable" theories from "non-renormalizable" theories. Of course, this can be done if we write down a non-relativistic theory as a deformation of a relativistic theory, and this is what this groups does, too. Nevertheless the number of new terms, once you allow the Lorentz symmetry to be broken, is again huge. Moreover, I think that the lessons of 1905 are serious lessons, and breaking the Lorentz invariance explicitly should also be accompanied by breaking of the rotational invariance, and I see no reasons to do so. Let's stop criticism for a while.

What theory do they consider? Take the usual Maxwell action in four dimensions, and imagine that you decide to deform it in some way, by adding another action. What is the other action you know for a U(1) gauge field? Well, the Chern-Simons action. There is a problem: the usual Chern-Simons term only exists in three dimensions. However, that's not a problem for those who don't care about the Lorentz invariance. Just multiply the Chern-Simons 3-form with a general vector, i.e. a 1-form, to get a 4-form, and you can integrate the product over the spacetime. The vector picks a priviliged direction which is OK with you. Because the Chern-Simons action has an epsilon in it, you will break not only the Lorentz symmetry but also the CPT symmetry - which can happen once the Lorentz symmetry is gone. To make the things even more confusing, add an external current J that couples to the gauge field via the J.A term.

That was too natural so far. Let's make something more fancy. Reduce this four-dimensional Lorentz invariant theory to three spacetime dimensions (dimensional reduction). Moreover, don't reduce it along the priviliged vector discussed previously, but along a more general vector. In this case, the three-dimensional Lorentz symmetry will still be violated. If you write down some terms, you will discover mass terms of various types. Just do it and derive the equations of motion and solve them and draw several graphs. And don't forget to be excited that the results pick a priviliged reference frame (even though you know that it was your starting point). It's probably a good feature to violate the Lorentz symmetry.

Finally, let me admit that I am totally lost. I have no idea why they're doing what they're doing, whether it should be a physically realistic model or a mathematically interesting one: I just don't see the meaning of it all. This type of activity is what most of us would be doing today if we had no string theory. Combining random terms that apparently follow no deeper or organizational principles - terms extracted from an infinite chaotic ocean of arbitrary terms and their combinations - terms that are much more ugly and unjustified than the theories that are known to work. Sorry for being so skeptical; I might simply be dumb.

These colleagues first repeat a lot of the commercials about "Causal Dynamical Triangulations" that they've already written in many previous papers. The starting points are very obvious and sort of naive: try to define the path integral of quantum gravity in a discretized form. (It's like spin foams in loop quantum gravity, but you don't necessarily require that the details will agree.) OK, so how can you discretize a geometry? You triangulate it into simplices, and you imagine that every simplex has a region of flat Minkowski spacetime in it.

(That's not like loop quantum gravity - the latter assumes that there is no geometry "inside" the spin foam simplices - the geometry is concentrated at the singular points and edges of the spin foam.)

Then you write down the Einstein-Hilbert action many times and you emphasize that it is discretized. There are many other differences from loop quantum gravity: while the minimal positive distance in loop quantum gravity is sort of Planckian, in the present case they want to send the size of the simplices to zero and the regulator should be unphysical. Of course that if you do it, you formally get quantized general relativity with all of its problems: as soon as the resolution becomes strongly subPlanckian, the fluctuation of the metric tensor becomes large. The path integral will be dominated by heavily fluctuating configurations where the topology changes a lot and where the causal relations are totally obscured - and the results of these path integrals will be non-renormalizably divergent - at least if you expand them perturbatively. But this is simply what a correct, authentic quantization of pure gravity gives you.

These authors are doing something different in one essential aspect. They don't want to sum over all configurations, all metrics - the objects that you encounter in the foamy GR path integral above. They don't do it because they sort of know that pure GR at subPlanckian distances is rubbish. Instead, they truncate the path integral to contain "nice and smooth" configurations only. The allowed configurations they include must be not only nice, but they must have the trivial causal diagram as well as a fixed topology - namely S3 x R in their main example. Well, if you restrict your path integral to configurations that look nice, it's not surprising that your final pictures will look nice and similar to flat space, too. But it by no means implies that you have found a physical theory.

Any path integral that more or less works simply must be dominated by configurations that are non-differentiable almost everywhere, by the very nature of functional integration and by the uncertainty principle. One can often show that the path integral localizes, but that's just a result of theorems and calculations. One cannot define the path integral to include smooth and causal histories only. Such a definition simply violates the uncertainty principle as well as locality, if you make some global constraints on the way how your 3-geometry can look like. Consequently, it also violates general covariance, and you won't decouple the unphysical polarizations. If you also make global constraints about the allowed shapes as functions of time that cannot be derived from local constraints, you will also violate unitarity.

As far as I know, none of these "discrete gravity" people ever asked the question whether these theories are physical, unitary, and so forth. In fact, the subset of the "discrete gravity" people called the "loop quantum gravity" people declares quite openly that they don't care about unitarity at all. Unitarity is actually one of their enemies and they claim that it follows from time-translation symmetry, which is of course a misunderstanding of total basics of physics: unitarity is about hermiticity of the Hamiltonian, if one exists, while time-translation symmetry is about its time-independence. Unitarity is one of the concepts that must be destroyed by the revolution in physics that they've been planning for quite some time. ;-) They're just not getting that unitarity is about the probabilities being non-negative numbers that sum up to one, and that this rule must work in any context in quantum physics. I am afraid that the rest of the "discrete gravity" people does not bother to check these elementary physics questions either. That may be a good point to stop criticism because everyone knows it anyway that I don't believe that this line of research will lead to any usable new physics because it simply neglects some totally essential features of quantum physics.

At any rate, they show that these strange rules of the game admit some big-bang big-crunch cosmological solution described by some collective coordinates (a nice picture animates in front of your eyes), and they construct or propose a wave function of the Universe that depends on the observable representing the "3-volume of the Universe".

15th anniversary of Velvet Revolution

Tomorrow it will be exactly 15 years from the Czechoslovak Velvet Revolution in 1989. Because it was an amazing period of the Czechoslovak history, I believe that this anniversary deserves an article. Those of you who are interested in Central and Eastern Europe might want to read it.



Although Mikhail Gorbachov started glasnost' and perestroika in the Soviet Union already in the middle 1980s, these trends did not quite penetrate to Czechoslovakia. Despite the Czechoslovak communists' claims that they followed his process of democratization (namely of "přestavba" which means "re-building"), the reality was quite different. Václav Havel was in prison and the economic reforms were stuck. The lives of all people were "normalized" and they looked much like in the 1970s. Not much progress. Most people were frustrated. Socialism was a boring system, indeed.

If you open this address,

(the address would be translated as november.itoday.cz, itoday is an internet daily) you will see how the Czech internet news would look like if there were no revolution. The actual news about 2004, as described by hypothetical socialist journalists, are so absurd, so funny, yet so incredibly realistic! :-) (And some of them are pretty similar to the comments about the world events as heard from some left-wing commentators throughout the world.) They describe letters about the comrade Arafat's death; the struggle of the Iraqi people against the American imperialists; the help of the Czech engineers for their Syrian comrades that are being threatened by the USA; the new bummers for the dollar, and so forth. Unfortunately you don't speak Czech, and therefore the pages won't be too entertaining for you. They have chosen authentic language; as well as the typical symbols of the late years of socialism (such as the commercials with Mr. Egg - all commercials in the 1980s always started with the same logo).

For most of us, it was very hard to imagine that things could speed up. In October 1989, Eastern Germans started to escape to West Germany through the embassies in Budapest, Prague, and other cities. History was obviously moving on in other countries but Czechoslovakia looked frozen. The developments in Poland and Hungary were being pictured as chaos that must be avoided in Czechoslovakia. There were no signs that the Party was forced to change anything. Some people like to say that Czechoslovakia was completely controlled from Moscow - but the years 1987-1989 were a great evidence that it was not so. Unfortunately - because the Soviet Union was ahead!

However, on Friday, November 17th, 1989, the students were celebrating the "international students' day". Well, it was exactly 50 years after the Nazis closed the Czech universities and killed or arrested the most inconvenient students. Those active students in 1989 not only admired their predecessors in 1939, but they also wanted to show that they did not like the practises of the socialist totalitarian system.

As you know, the young participants of the demonstration in Prague were beaten by the socialist police. Those of us who listened to the Radio Free Europe knew what happened on Friday. Most people who were interested in politics knew about these events by Saturday, and it was becoming clear that something important was going on. There were some rumors that a particular student named Martin Šmíd was killed by the police. These rumors were not true - in fact, a couple of years ago, I exchanged a plenty of e-mails with exactly this Martin Šmíd. He advocated astrology while I don't believe this science too much. ;-) At any rate, he definitely survived.

There were other important and confusing details such as an agent of the Communist Secret Agency that pretended he was a student, but I don't want to bother you with these details.

Nevertheless the anti-socialist dissidents, famous actors, musicians, and other people were slowly joining this "children's revolution". Various groups of people began to write down petitions and organize strikes. On Monday, the revolution was already underway. Although we were high schools students, our role was more important than what would be reasonable to expect. We were able to elect the principal of the school, and we wrote our own petitions.

In the evening, there was always a big demonstration in Prague, and smaller demonstrations in other cities including Pilsen, my hometown. The demonstrations were frequent, and the biggest one in Prague attracted more than one million of people.

New leaders started to emerge - Václav Havel, Jiří Dienstbier, Václav Klaus, Valtr Komárek, Miloš Zeman, Jiří Bartoška, and so on. Many of them had had no political experience. Many of them were actors and musicians, and so forth. Some of these early leaders are still doing politics; most of them have returned to their older jobs.

The communists started to have problems with the workers, too. An infamous boss of the Communist Party in Prague, Miroslav Štěpán, was explaining to the workers of ČKD, a big factory in Prague, that no country in the world - neither socialist nor capitalist nor third-world country - can allow children, 15-year old children to decide who will be in the government. Thousands of workers started to scream: "We're not children! We're not children!" Obviously, he was in trouble. Such things would have been unthinkable 2 weeks earlier.

The demonstrations in the streets were incredibly lovely and peaceful. The people were very nice to each other. Everyone thought that they agreed about everything - which, of course, turned out to be false as soon as the communists were eliminated from the government, and other questions beyond "the same socialism yes/no" had to be answered. They were ringing the keys. And the developments were extremely fast. Imagine a country where nothing really changed for 20 years - and suddenly the leading role of the Party is eliminated, the president and the Party's chief resign, and a new president is elected although he was in prison 2 months ago - and everything happens without any violence whatsoever.

I was always proud about the velvet character of the revolution even though I have also had many doubts about that strategy every time the communists said something outrageous after 1989. Could we have reduced their influence more significantly by replacing the velvet with a tougher material? I am not sure about the answer... Czechoslovakia was nevertheless the only country in which the communists did not return to the government after 1989 - the social democratic party was revived and became strong (for a couple of years, at least - although they are the senior party in the current government, they received essentially zero votes in the last two elections).

At any rate, thousands of changes had to be made between 1989-1991. It was pretty easy to guarantee the freedom of speech and other basic human rights. Our first president Václav Havel became the symbol of all these changes and new philosophies. It was much harder to transform the most socialized economy in the world into a moderately vibrant emergent free market. Thousands of companies had to be privatized - and some of them did not have a bright future because they lost the Russian markets etc. The currency had to become convertible, controlled by free market currency exchange rates. Václav Klaus, a charismatic economist who was neither a communist nor a true dissident, was ready to realize this task, and although it was a difficult one and its realization could not avoid some problems, I think that the result was very good.

Václav Klaus symbolized the transformation process of the economy, and consequently, he became very unpopular among many people in the middle 1990s. Nevertheless, his popularity jumped well above 60 percent once he was elected the second Czech president in 2003 - of course, the main reason is that he is not responsible for the economy anymore.

Although there are many "usual" and "expected" problems facing the people, the Czech Republic and Slovakia are clearly much better off today. Back in 1989 we discussed the question how many years would we need to catch up with some western European countries, and even though some of our guesses were unrealistic, most of them were not that far off. Today, both parts of Czechoslovakia belong to the European Union. The countries' citizens can do (and have) virtually everything as our Western fellows who have not lived in socialism.

Monday, November 15, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Academic bill of rights

The goal of this article is to explain you why I support David Horowitz's Academic bill of rights, a proposed policy intended to increase intellectual diversity at the U.S. universities.

See

http://studentsforacademicfreedom.org/abor.html
http://frontpagemag.com/articles/ ... ID=12119
http://studentsforacademicfreedom.org/

Those of us who have lived in the totalitarian systems are sensitive about the possible use of the educational system as a tool of political indoctrination. You know, the communists made a lot of effort to control the society in all conceivable ways. They applied all available tools to eliminate the "anti-socialist" people from the universities or even from the high schools. They have modified the history textbooks so that the children would learn "the right stuff". As far as Czechoslovakia goes, the communists were executing the people in the 1950s, but they were using much more "peaceful" strategies to achieve their goals in the 1970s and 1980s.

The Communist Party was dreaming about the "perfect" universities - and other schools - where all scholars support the Party; oppose the United States of America and its president, especially if he's a Republican, as well as the American and international corporations; where everyone appreciates free healthcare and education, as well as special rights of the working class; where everybody criticizes private companies, privatization, as well as religion; where everyone believes that almost everything should be redistributed and/or taxation should be sufficiently high for all the social programs; where the people are ready to fight against the evil called the capitalism or imperialism.

A picture to moderate your political excitement: a new kind of seahorse:



They were simply dreaming about scholars that are useful to support their power and to help the Party realize its utopia. Even though they tried to fire all of their enemies, the communists never quite succeeded, and at least 50 percent of the people at the universities were criticizing the Communist Party and admiring the West, although most of them were doing so in the privacy of their homes only.

It may sound surprising or amazing, but the communists' dream has almost become true 15 years later. Surprisingly not in Czechoslovakia but rather in America itself. ;-) Indeed, try to read the previous paragraph, and you will have to probably agree that

  • roughly 90 percent of the scholars (professors, postdocs, students) at the well-known U.S. universities agree with most of the opinions listed in that paragraph
Well, I actually think that the numbers are a bit different and more subtle:

  • approximately 95 percent of political opinions heard from these universities are left-wing opinions
  • my estimate is that 85 percent of the people at these universities could be classified as left-wing people. This figure is smaller than the previous figure because the non-left-wing people are often being threatened, humiliated, and in some cases even "converted" into "liberals"
  • the percentage of the left-wing people is extremely high in various social sciences and humanities in particular (especially various cargo cult sciences); it is lower in economy, at law schools, and in "hard" sciences
Even though Harvard was known as the Kremlin on the Charles, I don't think that things are particularly bad here. Don't get me wrong: virtually all of my colleagues are left-wing, but I've never encountered any serious problems with them which would be caused by my belief that the left-wing ideology is not really a valuable material. Of course, I've had a couple of arguments, but at the end, they mostly understood that they lost, and sometimes they even understood the logic behind my opinions. The situation at Harvard is pretty good because of many factors like the following:
  • Harvard's current president, Lawrence Summers, is a very wise guy who always prefers rational thinking and hard science over biased political activism and ideologies based on a priori prejudices about the good and the evil. His membership in the Democratic Party certainly does not lead to anything wrong.
  • I think that we have other very smart and balanced "leaders" at various levels, like our department chair, but I won't discuss details.
  • Finally, the undergraduate students at Harvard today are more conservative than you might imagine, even though it is often more about their conservative behavior than about their philosophy...
Nevertheless, the number of stories about discrimination and humiliation of conservative students and scholars at various universities is just too large to be neglected. For example, a senior member of a body that hires a certain type of people for a rather attractive job at one of the Ivy League universities told me that "had [they] known that [a guy] had these political opinions [e.g. he supported the current US administration], [they] would certainly not have accepted him".

Conservative students at Columbia university were selling bakery with discounts for members of various minorities. And the reason why they got almost killed was that they included the college Republicans among the minorities. Of course that they seem to be the maximally discriminated minority at that university. Moreover, I feel that their left-wing colleagues realize that.

Finally, let me comment on some particular points extracted from the bill of rights
  • All faculty shall be hired, fired, promoted and granted tenure on the basis of their competence and appropriate knowledge in the field of their expertise and, in the humanities, the social sciences, and the arts, with a view toward fostering a plurality of methodologies and perspectives. No faculty shall be hired or fired or denied promotion or tenure on the basis of his or her political or religious beliefs.

Of course, it's important that there is no political key for "hard sciences". On the other hand, I find it obvious that the students - who are rarely left-wing radicals - have the right to get the right education for their money. They can't get the whole picture if they only hear one half of it. (I did not invent this slogan.) It's obvious that many departments of social sciences have overly left-wing faculties. In these politically flavored fields, it is often impossible to "prove experimentally" which viewpoint and which scientific work is correct and which viewpoint is wrong. It's a matter of political consensus. Therefore the left-wing as well as the right-wing people should be able to influence the process of hiring the right people. Obviously, if it is done so, the percentage of hired conservatives will grow.

  • No faculty member will be excluded from tenure, search and hiring committees on the basis of their political or religious beliefs.

Well, I know examples where this rule was violated, and I think it is very wrong. On the other hand, there are - and there have been - many renowned non-left-wing professors at the well-known universities, e.g. the late Robert Nozick.

  • Students will be graded solely on the basis of their reasoned answers and appropriate knowledge of the subjects and disciplines they study, not on the basis of their political or religious beliefs.

I think that this is an obvious criterion that should already be followed today, although I doubt that it always is.

  • Curricula and reading lists in the humanities and social sciences should reflect the uncertainty and unsettled character of all human knowledge in these areas by providing students with dissenting sources and viewpoints where appropriate. While teachers are and should be free to pursue their own findings and perspectives in presenting their views, they should consider and make their students aware of other viewpoints. Academic disciplines should welcome a diversity of approaches to unsettled questions.

This seems as an obviously legitimate point, too, and I have already commented on the "consensual character" of knowledge in many of these disciplines.

  • Exposing students to the spectrum of significant scholarly viewpoints on the subjects examined in their courses is a major responsibility of faculty. Faculty will not use their courses for the purpose of political, ideological, religious or anti-religious indoctrination.

Sure. Incidentally, some students are really shocked when they first learn that there exist influential right-wing and libertarian think tanks, for example. Well, a student of political science may pay tens of thousands of dollars, but if he does not know, after the several years of study, who Ann Coulter or the Cato Institute is and what are their points, he will remain a naive simpleton who does not understand politics. I certainly believe that a fair representation of different political opinions at the campuses is more important for their intellectual life than a proportional representation of nationalities or genders.

  • Selection of speakers, allocation of funds for speakers programs and other student activities will observe the principles of academic freedom and promote intellectual pluralism.

There have been many surprising events in which the money of all students were used to pay e.g. Michael Moore's speech. This guy is not really thin and that's not the only reason why he demands tens of thousands of dollars for one of his shows. Of course, the conservatives would not be paid, and the right-wing students must obviously feel suppressed.

  • An environment conducive to the civil exchange of ideas being an essential component of a free university, the obstruction of invited campus speakers, destruction of campus literature or other effort to obstruct this exchange will not be tolerated.

Obviously, that should be one of the features at the universities, but I don't know particular examples of destruction of literature etc. ;-)

  • ... Academic institutions and professional societies formed to advance knowledge within an area of research, maintain the integrity of the research process, and organize the professional lives of related researchers serve as indispensable venues within which scholars circulate research findings and debate their interpretation. To perform these functions adequately, academic institutions and professional societies should maintain a posture of organizational neutrality with respect to the substantive disagreements that divide researchers on questions within, or outside, their fields of inquiry.

I am not quite sure about the realization of this point, and there may be various detailed rules how to enforce the bill of rights that I would not endorse. Nevertheless, the whole proposal looks like a clear piece of progress to me.


Sunday, November 14, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Desktop Google

Microsoft has started its Google-killer at

http://beta.search.msn.com/

Indeed, in many respects, it is better than Google - 10 times as fast, for example. Besides the advantages, there seems to be one disadvantage: the ordering of the pages just does not seem as good as Google's. Giving the right importance to various pages is something that the Google guys have become very good at, and Microsoft will need more time to catch up, I think. However, when it's done, it's conceivable that Microsoft will take over. They should also choose a better URL.



But what I want to tell you primarily is that there is a great desktop version of Google. Download it from:

http://desktop.google.com/

It will need a couple of hours to make an index of your computer, but then you will be able to search through all your local files containing some text, using the usual Google interface! Recommended!

Saturday, November 13, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

After the Sunset (spoilers)

I believe that Xmen II was the last movie I've seen in a regular movie cinema in the States. Last night we picked the movie rather randomly, and After the Sunset was the winner.

It's a good comedy similar to James Bond 007, even though it's perhaps a bit shallow. Well, the Czech readers may appreciate my comment that the movie may be even more similar to James Blonde 007. ;-) Max and Lola (Pierce Brosnan and Salma Hayek), a very successful pair of thiefs of jewelry, decide to retire. They move to Bahamas - which is a very nice place where Viktor Kožený, our former colleague from Harvard, has also moved.


  • Incidentally, snow has arrived to Massachusetts!

However, their traditional opponent, the hapless FBI agent Stan Lloyd (Woody Harrelson), visits them. He shows Max a huge temptation - a very expensive diamond located in a large ship. Although Max replies that he can't get this one, finally he steals this one, too (well, he does it during scuba-diving). Meanwhile, Max and Stan are fishing together; they sort of sleep together, after Lola kicks Max out from their house: other FBI agents find them together in the bed which is funny and embrarassing.

At the end, Stan nearly believes that he is able to defeat Max this time (and privatize the jewel for himself). But the reality is different - and Max once again remotely controls Stan's car. A very important part of the movie are various scenes with Lola who shows many things, and she looks good. I was surprised to learn that she was born in 1966. At any rate, it is likely that I will forget about the movie pretty soon...

Friday, November 12, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

A curious truncation

Savdeep Sethi from University of Chicago was the duality seminar speaker yesterday, despite the holidays.

His title was:

A curious truncation of N=4 supersymmetric Yang-Mills

He chose to present a blackboard talk, even though PowerPoint was another option. The talk focused on his recent paper with Anirban Basu and Michael Green. Savdeep is, of course, a very interesting speaker. OK, what's the problem?

Choose a correlator of some operators in N=4 super Yang-Mills, and try to calculate the derivative with respect to tau, the complexified coupling constant. You will obtain a term that encodes the explicit dependence of the operators on tau, but you will also obtain a "dynamical" term arising from the fact that the action is tau-dependent. The latter can be written as a correlator of the previous operators with one more insertion added. This extra insertion is essentially the integral of the Lagrangian.

A funny feature is that one can take the operator called the Lagrangian and construct all possible supersymmetric variations of it. One obtains a short multiplet that contains a lot of other "special" operators such as the R-symmetry currents. Savdeep played with these special operators in many ways and he expressed various correlators as Eisenstein series (modular forms). Also, he studied how these correlators transform under SL(2,Z). His most favorite correlator was a correlator of 16 fields. He also considered a "gauge connection" on the space of complex coupling constants which was interesting on its own right.

As far as I understand, his curious truncation is the gauge theoretical counterpart of the truncation of the string theory to supergravity (operators whose dimensions remain finite in the large N limit). Yes, I probably misunderstand something because this does not seem too curious - in fact, this is how AdS/CFT started. Moreover, we (with Mina and perhaps others) were a bit confused whether you can really and consistently truncate string theory into supergravity in this way. All of us understand that classically - or equivalently, with non-planar diagrams neglected - one has a beautiful theory of supergravity, but we thought that it's not possible to define any quantum theory, or equivalently a theory with a finite 't Hooft's coupling, that would contain supergravity only. Correspondingly, such a truncation should be invalid in the gauge theory, too.

Because I don't understand this basic point too well, I must redirect all interested readers to their paper. If you find this stuff interesting, reading this efficient paper seems as a good investment of your time.

Thursday, November 11, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Some pictures

For those who want to see some random photographs, a couple of links follows (MSIE recommended):

I will probably post several newer collections later when I have more time. Incidentally, some people still don't know the following funny things:

Wednesday, November 10, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

News: the world

For many people, this blog is the primary source of information about the world, and therefore it is reasonable to mention a couple of events that occured during the last hours:

  • The weather is very cold in Massachusetts. The record cold temperature 26 Fahrenheit from 1992 was improved to 25 Fahrenheit in 2004. (We have had record cold temperatures last year, too.) Note that the cold weather supports the scientific theory about global warming, much like warm weather, hurricanes, absence of any winds, big fluctuations, as well as small fluctuations of the weather - all of these things are disastrous consequences of our production of CO2. The global warming theory is absolutely robust (permanently safe, as Glashow would say if it were string theory) because whatever happens supports this theory (except the future possible first signs of rational thinking of the GW proponents, which would not be the best tool to support the conjectured mechanisms).
  • Microsoft will launch its new search engine tomorrow. This new search engine will have twice as good technology compared to Google's. Bill Gates admitted that "Google kicked our butts". However, Microsoft did not give up. Microsoft will catch up and surpass the competitor, and its profit will be twice as big, too, Ballmer explained. Also, Microsoft has solved all the disputes in the USA by having paid Novell half a billion USD. (Well, Novell is probably not the only party that would become satisfied with such a gift.)
  • However, some bureaucrats in Europe continue to be obnoxious. Some of these eurobureaucrats insist that the Windows Media Player must be removed from Windows. It's just outrageous! It's a way to add problems to the customers as well as Microsoft. One can imagine how devastating could be the actions of the eurobureaucrats against a regular European person or company if they don't hesitate to present these absurd demands from a powerful American company. Who voted for these people in Brussels? I certainly did not.
  • Yasser Arafat's health has deteriorated again. He has suffered from brain hemorrhage, liver dysfunction, and so on, and different people (wife, advisors, other Palestinian politicians) propose different theories about Arafat's life or death in a sequence of events that can be called Propaganda war about Arafat's health. Arafat will officially die tonight, Eastern time.
  • Various crazy guys equipped with rather primitive weapons try to fight against the US military in Fajullah, Iraq. The Americans control 70 percent of the city. Every time the Iraqis throw an anti-tank grenade, they're immediately detected from the air and eliminated. It's not quite clear whether these - often young - guys realize that they are commiting suicide. Well, no doubt, they're brave guys, but by offering their lives, they undoubtedly increase the average intelligence of the humankind.
  • Related gunmen have kidnapped at least two members of the family of Iyad Allawi. They want the USA to surrender in Fajullah in the next 48 hours, otherwise they plan to kill the relatives.
  • The euro has broken the psychological barrier of USD 1.30 for the first time. However, the September US trade deficit shrank to 51.6 GUSD (lower than predicted 54 GUSD) and the US jobless claims in the last week were lower than expected, too (333 kilopeople), and therefore the euro quickly returned to USD 1.295 or so. Note that the sustainable market value of 1 euro - necessary to avoid recession in Europe - is roughly USD 1.05. Last week, the marvelous figure of 337 new kilojobs created in October shocked the forecasters who had predicted one half of that amount. Also, the inflation expert Alan G. (not Guth, however) is expected to raise the rates in the USA from 1.75 to 2.00 percent today which would make the rates in USA and Europe equal (recall that the UK have roughly 4.75 percent!). Note added later: indeed, he raised the rate to 2.00.
  • Also, the oil is getting cheaper (47 dollars, lower than the record 55 dollars last month).

Tuesday, November 09, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Fusion reactor (ITER)

The European guys seem pretty convinced that the research of thermonuclear fusion can lead somewhere, although not much progress was seen in the last 50 years.



The International Thermonuclear Experimental Reactor (ITER) may be built in Cadarache, France, or in Japan, and the different countries are competing to "win" the project.

Brussels has "warned" that it may go ahead and build the first reactor with anyone who will be friendly enough.

http://www.cnn.com/ ...

I am not sure what are the estimated chances that such a reactor will work and it seems as a more important question than the location. ;-) It's pretty clear that if the thermonuclear fusion reactor worked, many other developed countries would try to build their own - because it would be a big deal.

Such a reactor would be much more environmentally friendly and more efficient than the fission reactors. Moreover, the "fuel" could essentially be the water in the world's oceans.

Monday, November 08, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Homosexuality linked to fertility genes

Physics is not the only science, biology is a science, too.

Scientists at the University of Padua, Italy, studied the genetic components of homosexuality.

http://www.signonsandiego.com/ ...
http://www.telegraph.co.uk/ ...
http://www.newscientist.com/ ...
http://zdravi.idnes.cz/ ...
http://www.advocate.com/ ...
http://news.bbc.co.uk/ ...

Andrea Camperio Ciani and his team did not quite make a hard biological experiment; it was rather a poll of 98 homosexuals and 100 heterosexuals, including 4,600 of their relatives.

Nevertheless the outcome seems to be that homosexuality is contained in a gene associated to the X chromosome. Recall that women have XX while men have XY, which means that his Y must be inherited from the father, and consequently his X must be inherited from the mother.

In other words, homosexuality of men is inherited purely from the mother.

The Italian statistical analysis showed that homosexuality was correlated with homosexuality of other relatives. More importantly, it has shown that that mothers and aunties of homosexuals were more fertile (something like 2 vs. 1.5 daughters and sons).

If one believes these results, the homosexual gene is carried both by men and women, and it causes homosexuality of men, and hyper-heterosexuality (or fertility) of women. This trivially resolves the well-known paradox due to Darwin why don't the homosexual genes disappear: the women compensate for the men.

Topological M-theory

We've spent some time by waiting for - and looking forward to - the new paper by Dijkgraaf, Gukov, Neitzke, and Vafa, and now it's finally here:

http://www.arxiv.org/abs/hep-th/0411073

Their goal is to unify various theories of gravity based on p-forms: topological theories of gravity, to use a simpler language, as manifestations or compactifications of the same seven-dimensional theory ("topological M-theory").

...

The conjectured seven-dimensional "master" theory is supposed to be a UV completion of the so-called Hitchin theory. It has relations to the G2 holonomy metrics, and stable p-forms, and by assuming the solution (background) to have various fibered forms, they "dimensionally" reduce the Hitchin theory (and its completion) to various lower-dimensional theories, namely those:

Sunday, November 07, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

This week 208: analysis

I am just reading "This Week's Finds in Mathematical Physics" number 208 by John Baez. Powerful stuff.

John Baez describes a conference at the Perimeter Institute. What was the topic? Well, it was obviously loop quantum gravity, but the organizers chose a pretty self-confident title that includes the words "Quantum Gravity in the Americas". Wow.

These conferences seem to be a spiritual continuation of the conferences decades ago, such as the 1962 general relativity conference in Warsaw. In a letter to his wife, Feynman wrote:

  • I am not getting anything out of the meeting. I am learning nothing. Because there are no experiments, this field is not an active one, so few of the best men are doing work in it. The result is that there are hosts of dopes here (126) and it is not good for my blood pressure. Remind me not to come to any more gravity conferences!

Let's mention that Feynman himself derived the Feynman rules for general relativity in 1963. He also showed that the tree diagrams agree with the classical theory. Because of these and other contributions, it is clear that his opinion about quantum gravity mattered.

Saturday, November 06, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Czech senate elections

All my left-wing readers who are depressed because of their loss on Tuesday may become happier if they learn that other socialist parties are doing much worse.

The Czech Republic has voted its Senate and also various regional bodies.



Incidentally, most of the Czech kings were called Vaclav (Wenceslas), and the first two presidents of the Czech Republic follow the tradition. The picture shows Vaclav God-knows-what's-his-number, a Czech emperor and wise guy.

I must introduce for you the main Czech parties, so that you know the basic players:

  • ODS, the Civic Democratic Party, are the Czech "Republicans". Well, they're not quite as conservative as the GOP. In fact, ODS is the ideal party because it is a "liberal conservative party". Of course, the word "liberal" is supposed to mean "libertarian". ODS was founded in 1991 by Vaclav Klaus, the father of the Czechoslovak economic transformations after the Velvet revolution. Klaus - a very bright free-market advocate who is a friend with the people like Margaret Thatcher, Milton Friedman, and others - was responsible for many important decisions, including the unpopular ones, which made him an unpopular prime minister. However, he was finally elected as the president after Vaclav Havel, who used to be one of two main Klaus's rivals - the other being Milos Zeman discussed below - and he is a highly popular president - which means a counterpart of the British queen: the fairy-tales about Klaus's alleged ignorance have mostly evaporated. Incidentally, Klaus is just visiting the USA and Canada.
  • CSSD, the Czech Social Democratic Party, are the Czech "Democrats" who are currently leading the government because they won the elections in 2002 (and in 1998) with more than 30% of the electorate. The social democrats have existed in Czechoslovakia for more than a century, but they became irrelevant after the communists took over in 1948. (More precisely, they were unified with the communists.) Milos Zeman, the other rival of Klaus, who is a rather intelligent person and who has been a big fan of a fancy alcoholic drink (Becher's lemonade) revived the party around 1990. An unimportant born-again party was changed into an important player that absorbed most of the left-wing voters that would otherwise vote for the communists. Czechoslovakia was the only country in which the former communist party was marginalized. Zeman became the prime minister after Klaus in 1998, but was replaced by Vladimir Spidla, a rather boring and very "progressive" guy. It could not work indefinitely, and Spidla was finally removed from the chair of CSSD (and the government) in summer 2004, and replaced by Stanislav Gross. Gross is 35, the youngest prime minister in Europe today, but he looks roughly 15-20.
  • KSCM, the Communist Party of Bohemia and Moravia, is the Czech Republic's part of the former Communist Party of Czechoslovakia (founded in 1921) that has controlled Czechoslovakia between 1948 and 1989. It has not changed anything about its 19th century ideology of marxism-leninism. The current leader is Miroslav Grebenicek, a rather popular gentleman among many 80+ years old people. Grebenicek comes from a good family - his father was one of the communist killers in the 1950s.
OK, what about the recent elections? One of the reasons that Spidla was eliminated in summer 2004 - well, they "punished" him by turning him into a member of the European commission - was the total collapse of CSSD in the elections to the European Parliament. The turnout was below 30 percent and ODS was the clear winner. The main government party, one that had more than 30% in the 2002 elections, only won two seats in the European Parliament out of 24. ;-) Note that it is roughly 8 percent - the U.S. Democrats currently with 49 percent still have a very long way to go!

Well, that was bad enough even for the Czech socialists, and they replaced Spidla by Gross. Stanislav Gross has been one of the two most popular Czech politicians of the last 5 years, especially because he looks like a child, but also because he has relatively good diplomatic skills.

However, in the elections today, ODS became the clear winner in 12 regions out of 13 (these are Czech counterparts of the "states"). The exception was the Southern Moravia where the KDU-CSL (The Christian Democratic Union - the Czechoslovak People's Party) became the winner. The ODS candidates have made it to the second round in 25 out of 27 Senate districts. In 9 of them, their rivals will be communists who were more successful than the social democrats.

In Pilsen - which is my home town where the modern beer was invented - the ODS's mayor Jiri Sneberger was able to become a senator already after the first round because he has earned more than 50 percent of votes. Yes, I would vote for him, too.

Obviously, Gross's innocent face does not seem to be enough. If you think that the reason for the recent successes of ODS is the natural right-wing character of the Czechs, which will allow this nation to compete with America, you're almost definitely wrong. The main reason is that the social democrats are currently responsible for the government, and the Czechs like to complain 90% of their time about the government that is supposed to solve all of their problems. Unluckily, it's been their government for 6 years. This fact makes the job for Miroslav Topolanek, who became the chairman of ODS after Klaus a couple of years ago, slightly easier.

Incidentally, the Czech president Klaus may have been rather skeptical about most wars that the States recently started - including Kosovo and Iraq - but as a rightwinger, it is not surprising that he welcomes Bush's win. "Bush is a standard bearer of American values," Klaus said.

Incomprehensible world?

That's another light, physically philosophical posting from sci.physics.research where backdoorstudent replied to one of my texts.

When I wrote:

"You don't seem to appreciate how amazing it is that the world satisfies some simple enough comprehensible laws at all,"


backdoorstudent replied:

  • Of course I do. I think almost everybody reading this newsgroup does.
I've quoted his sentence in order to highlight that he contradicted himself below. The exchange continued like that:
  • I know. And I'm getting sick of hearing everybody parrot it around as their mantra. And if you insist on presuming that it must be that way you may miss out on finding out something more accurate about the world. Because our experience of the world being this way is a very short one so far, and it is an idealist extrapolation to think it will continue forever. I am not saying I believe it won't. I'm just saying keep your mind open to other possibilities.
I cannot really keep open mind about this question whether science should eventually declare the world incomprehensible. Of course that science cannot declare the world incomprehensible - simply because its purpose is just the opposite. If science ever does so and declares the world (or a piece of it) permanently incomprehensible, it would mean that science ceases to exist. What you say is a logical oxymoron, as I describe below in more detail.
  • Would you really be surprised if the world was ultimately incomprehensible?
First of all, the world is definitely not *completely* incomprehensible. It's not only largely comprehensible, but we have already understood quite a lot.

Friday, November 05, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Albion and Bernard: talks

Yesterday, Albion Lawrence gave a pretty interesting and very well-prepared Duality Seminar on his work with John McGreevy (who is visiting us, too) about soft SUSY breaking terms from FI D-terms in type II string theory.

Thursday, November 04, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

The Pioneer anomaly

The last paper on gr-qc today is about the Pioneer anomaly:

http://www.arxiv.org/abs/gr-qc/0411020

It seems that it is a rather attractive topic for many people - and there have even been conferences dedicated to this problem. See, for example,

http://www.zarm.uni-bremen.de/Pioneer/

What's the problem?

Two spacecrafts (Pioneer 10 and Pioneer 11) were launched in 1972 and 1973. They have done a good job and informed us about the distant planets in our solar system. Eventually NASA lost contact with them.

Nevertheless, the radio measurements of the position of the spacecrafts during the last years of their existence seem to show a puzzle: it seems that there is a universal unexpected contribution to the acceleration towards the Sun whose magnitude is roughly

a = (8 +- 1) x 10^{-10} meters/second^2

A shocking feature of this value of a is that it seems to be the same acceleration as the critical acceleration relevant for the MOND theories that replace dark matter, see another article on this blog

/2004/10/mond-and-holography.html

More precisely, the value of this acceleration is again a=Hc - it is the Hubble constant multiplied by the speed of light, plus minus roughly ten percent. If I calculated correctly, the usual Newtonian acceleration at the distance of 70 AU from the Sun (where the Pioneer anomaly was measured) is roughly 1.2 times 10^{-6} meters per second squared which is approximately 1500 times bigger than the anomalous acceleration a.

In other words, the integrated deviation from the expected position of both spacecrafts is roughly 400,000 kilometers in both cases - that's like 10 thousand of marathones!

Most particle physicists and string theorists would of course be skeptical about the existence of this new effect: we know from the observation of planets that such a large effect does not seem to exist for planets. Moreover, we have tested the equivalence principle pretty well, and a special "universal force acting on the spacecrafts" violates the equivalence principle. Furthermore, we have already learned that the people in NASA are sometimes capable to make as stupid errors as confusing inches and centimeters.

Nevertheless the numerical value of the acceleration and the possible relations with MOND (and holography) makes this topic sufficiently interesting for me so that I decided to write this short article, and encourage you to write your knowledge and opinions about this topic. Don't you think that there can be some new effect, associated with the breakdown of GR at very small accelerations, at least for small enough objects, associated with the breakdown of locality in holographic theories?

Obviously, Europe finds this topic more attractive, and some proposals to launch a spacecraft (well, NASA with LANL with the University of Bremen) whose only purpose is to measure its own motion have been suggested:

http://physicsweb.org/articles/world/17/9/3/1

These new probes could increase the precision by a factor of one thousand, and they should almost definitely settle the question whether the anomaly is a result of

  • a stupid systematic error,
  • the influence of new dark matter at the boundary of the Solar system
  • or a proof of new physics.

Arafat dead?

I am faster than CNN, nytimes.com, FOXnews, ABCnews, CBSnews, and others, to tell you that according to the prime minister of Louxembourg as well as the Israeli TV that received the news from the French sources, Yasser Arafat just died. He's been declared clinically dead by his doctors.

However, the Palestinian prime minister denies the information, citing Arafat's wife. The spokesperson of the hospital rejects the news, too. Nevertheless, all the semi-reliable statements are compatible with the conjecture that Arafat is technically alive, but brain dead.

Let's now assume that the news is correct after all and Arafat will never wake up again.

It's always sad if someone whom you know dies. Although Czechoslovakia played a rather important role in establishing the state of Israel, the communists eventually allied with Arafat, and the Palestinian state was presented as our friends.

Later, one had to learn about all these Arab terrorists in Israel - and Yasser Arafat was provoking them. Although Arafat dedicated his blood after 9/11, and he was not such a terribly negative figure after all, I am pretty sure that the post-Arafat era will be a bit happier for Israel and there will be new chances for peace in Israel and Palestine. Arafat has been the only true leader in Palestine, and the Palestinians will probably become a bit frustrated without him.

Wednesday, November 03, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Kerry concedes, Bush triumphs

This may have been one of the most exciting and dividing polls in the history. Let's state some basic facts:

  • Nima Arkani-Hamed and other people around don't look desperate, in fact they laugh, which is a very nice picture to see. Yesterday they truly believed that Kerry's victory had been programmed...
  • Kerry may have surrendered too early - I thought that there was still a mathematical possibility that most of the ballots in Ohio voted for Kerry, and they would be enough for him to win the state. But something may have changed recently. Perhaps, they realized that the missing ballots couldn't be overwhelming pro-Kerry...
  • Nevertheless, Kerry has proved that he (with Edwards) was a very realistic alternative that had a significant chance to win. He also seems to be a realistic politician, and unlike Al Gore, he avoided the painful process of questioning everything and everyone. In my opinion, Kerry deserves respect for that, especially because the Democratic Party hired thousands of lawyers and paralegals whose task was to question every vote they could...
  • Nevertheless, what Kerry has shown was not enough. Bush has convinced most of the voters that he is the right man for the White House. He is the guy whose acts agree with his beliefs. He is the guy who looks better and whose way of thinking is more transparent and comprehensible for the people. He is the man you can rely upon. He is the right man to continue the War on Terror (plus other related mess) that he was forced to start on 9/11. He knows in which way the taxes should move for the people to feel richer and more free. We know better what to expect from him...
  • I also understand that Kerry did not come to greet his fans in Boston during the rainy night. He probably realized at that point that his chances were not too high. On the other hand, the fans who waited in the rain were most likely left-wing fundamentalists who would have little understanding for Kerry's growing decision to surrender...
  • Bush has clearly won the popular vote, roughly by 3 million votes, if I remember well. Because a large part of the left wing has criticized Bush for not having won the popular vote in 2000, those arguments made them much weaker in 2004 because now they would need to argue that the popular vote does not matter at all, even if the difference is 3 millions. Bush's victory in Florida was much more decisive than in 2000...
  • Those 11 states that were deciding about the consistency of the term "gay marriage" showed that this topic is not too controversial in these states, and all of these states decided that the marriage is a union between one man and one woman, and to avoid misunderstandings, the definition should become a constitutional law. Of course, this success of the traditionalists does not mean that it could be repeated in all other states of the USA...
  • The turnout was amazingly high - which is connected with the fact that the US society is very polarized. George Bush has not been successful yet to become a "uniter", as opposed to "divider" as he promised in 2000 - but of course, it is mostly because of the difficult tests that made his job much harder...
  • In my opinion, the American people feel that the politicians really represent them, and they are positively excited about their candidates, and they understand that the politicians fight for specific issues: this connection is much weaker in Europe, I think, much like the turnout (for example, the disastrously low turnout in the polls for the European Parliament)...
  • All formal and technical procedures went smoothly, it seems. The USA were slower in reporting the final results than Botswana, a country in the southern part of Africa, and this fact is related to the lack of unified technical rules how the votes should be collected and counted. In the European Union, I am pretty sure that they would try to introduce unified hardware and software for all countries, and so forth. In the USA it's not the case. It is not such a big problem - nevertheless, the superslow results from Ohio should mean that the Ohio system of collecting and counting votes will be banned, and replaced by a system from another state (or county). I encourage the people in Ohio to realize that their current system is pathetic...
  • The GOP strengthened in the Congress and the Senate, and probably also with the number of its governors. Tom Daschle (D) was the first speaker of the house in the last several decades who was not re-elected. A Republican from South Dakota will replace him...
  • George Bush is a winner, but the Left has its winners too - for example, Hillary Clinton is one of them. I am sure she can't wait until 2008 anymore...
  • My guess is that Osama bin Laden is among the losers because his recent video looked like an attempt to prevent Bush from being re-elected. This strategy may have worked in Europe, but it is not enough for America. Although Osama is just one of the most obnoxious killers in this world, he would love to take credit for the destruction of the Soviet Union and other events in the history. He's definitely less important than he tries to show...
At any rate, it seems that George Bush is going to stay in the White House, and now his presidency seems to be more legitimate and justified than four years ago. He may be a slightly different president in the second term - the changes may go in both ways. I wish him (and all of us) less tough tests - such as 9/11 - in the second term; the right decisions to avoid serious problems (casualties; potential problems in the economy; anger of other people). I wish him to have the opportunity to become a uniter after all.

If you compare 2000 and 2004, many things are different. In 2000, when Bush was elected for the first time, the US economy was just ending a period of impressive growth, budget surpluses, and so forth, but the bubble had already collapsed, and people knew that they would be entering a less shining period. However, almost no one realized how easy it was for an Arab jerk to destroy the skyscrapers in Manhattan, with thousands of lives in them. Also, no one realized that there is a lot of dirt and fraud waiting in companies such as Enron.

Today, we know a little bit more. We know that the terrorist attacks may take place in the Western countries. We were reminded that large companies may become messy, and they may go bankrupt. There are many new policies to prevent the terrorist attacks and corporate fraud - and there are new chances that these policies might be effective. On the other hand, all the people in the world may be luckier this time. The frequency of terrorist attacks could decrease, and the world may be entering a happier and more peaceful era. Moreover, the first derivative and the second derivative of the economy looks better than in 2000.

All these things seem promising. Will Bush be able to avoid disasters in his second term? Will Iraq become stabilized after the elections in January 2005? Will most of us agree, in a couple of years, that the war in Iraq was a good idea in the long term? Stay tuned...

Monday, November 01, 2004 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Gia's landscape and other new papers

I've decided to remove the article about women in physics - as well as the discussion below the article - because I am afraid that the opinions about this controversial topic that were advocated in that text could be misunderstood in such a way that they would damage Harvard University. At the same moment, I re-enabled anonymous comments under my articles. Thanks for your understanding, and apologies to those who have found the article insulting.


Back to physics:

It may be fun to try to say a couple of words about each hep-th paper that appeared tonight:

  • http://www.arxiv.org/abs/hep-th/0410285 - Neutrix calculus - This paper seems quite bizarre to me. The authors propose "Hadamard's regularization" of the divergences in quantum field theory, which is based on some specific subtractions of divergent pieces, leading a particular finite value. Well, zeta-function regularization of the sum of integers in string theory may look similar, but in the latter case we have methods to show that such a procedure leads to nice results that satisfy the axioms of CFT, and so forth. In their case, it just seems to me that by removing the infinity, they are converting a correct (divergent) result into a random incorrect (convergent) result that will preserve neither unitarity (of the S-matrix elements, for example), nor locality (of the Green's functions) or gauge symmetries (of everything). The authors don't ask the question whether their theory makes any sense at all. Instead they propose strange statements that non-renormalizable theories are now OK, and so forth. Also, it's not quite clear whether they want to remove the divergence of a particular n-loop amplitude, or the divergence of the asymptotic sum of all terms. In the latter case, the perturbatively non-renormalizable theories are still wrong.
OK, my guess is that we should spend more time with Gia's landscape paper.
  • http://www.arxiv.org/abs/hep-th/0410286 - Gia Dvali's anthropic solution of the hierarchy problem - There are also other interesting papers on the web, but this one, I think, will attract the attention of many people. The paper is based on Gia's previous work with Vilenkin, but this is my first encounter with these papers.

Gia Dvali joined Nima Arkani-Hamed and Savas Dimopoulos, friends (applied string theorists) who are his co-fathers of the large extra dimensions, and proposed his own version of an anthropically inspired solution of the hierarchy problem.

Recall that Nima and Savas have proposed Split supersymmetry

http://arxiv.org/abs/hep-th/0405159

that argues that it's OK if the Higgs is unnatural and tuned, but with this single sacrifice, one may argue that SUSY should be broken at a high scale and gluinos (dark matter) should be the only light superpartners, which also preserves the success of gauge coupling unification.

Gia Dvali's approach has similar goals and methods, but different "details". Gia's scenario is based on these rather simple ideas:

1. The Higgs mass is effectively a dynamical quantity, which arises from an interaction with a 4-form field strength F4 (the term is Higgs^2.F4^2) induced by some heavy domain walls (2-branes)

2. This mass is dynamical, but discrete. To solve the hierarchy problem, one needs to find a reason why the small masses are preferred. Gia follows Michael Douglas's anthropic counting where the number of vacua measures how natural something is - but in a one-parameter family of vacua only,which may be more meaningful.

Gia's explanation why the small mass is preferred is a kind of "beauty is attractive" argument. It seems that he just postulates that the density of vacua diverges around the desired point because of a power law - without showing why the exponent has the correct sign etc.

(So far, this does not look quite satisfactory to me. You can always say that some quantity XY is small because there is some underlying approximate symmetry that changes XY by a factor, which effectively makes log(XY) a more natural quantity, and the parameter XY is then expected to be much smaller. Is it an explanation? To be more quantitative, I don't know how he gets 10^{-16} as opposed to 10^{-infinity}, for example.)

He says that the required symmetry to make the small mass an "attractor" is a brane conjugation symmetry; he argues that a second Higgs doublet is needed; and he surprisingly relates the Higgs physics with the QCD scale; also, he claims that the quarks' Yukawa couplings are then severely constrained. All these statements may be very interesting.

I have not had time to study all these points in detail yet, but I hope that someone will write her or his understanding below this article. Of course, something like a realistic constraint on the Yukawa couplings is necessary to make the model predictive - otherwise, the amount of input equals the amount of output.

  • http://www.arxiv.org/abs/hep-th/0410287 - Lorentz violating terms - I don't really understand the motivation of such papers too well. As far as I know, there is no reason to believe that the Lorentz invariance (of local phenomena where curvature can be neglected) is broken by the laws of physics. When we sacrifice Lorentz invariance (which incidentally allows us to violate the CPT theorem, too), the spectrum of possible theories is huge, and I don't understand what's the organizing principle that they only consider this theory and not a much more general theory. Well, yes, maybe if one still requires a certain amount of supersymmetry, like these physicists, the situation may be more constraining. If Lorentz symmetry is broken in string theory, it is always, in some sense, a spontaneous breaking - by matter or condensates of actual fields. Moreover, the authors say that their motivation comes from astrophysics, but they study some Chern-Simons terms in 6 and 10 dimensions.

OK, let's now go from CPT violation to M2-branes.

  • http://arxiv.org/abs/hep-th/0410288 - Supermembranes with central charge - The authors like to talk about symplectic manifolds and calibrations, but I think that there may be interesting physics in the paper, too - although the number of equations is very small. If I understand well, they want to wrap an M2-brane n times on a genus g Riemann surface. If you want to connect all these n sheets into a single membrane, you must put n special branching points on the Riemann surface. And the authors argue that these special points give the membrane a sort of central charge - it's not quite clear to me yet what this central charge of a membrane is. There is a T-dual perspective with D2-D0 bundles. I remain skeptical about the paper, especially because the authors claim strange things, e.g. that the spectrum of a membrane becomes discrete, and so forth. The interactions of membranes can never be set to zero, and a membrane is always able to emit a smaller membrane if it has enough energy, which should make the spectrum continuous in all cases.

Now a generalization of the ADM mass for branes.

  • http://www.arxiv.org/abs/hep-th/0410289 - Y-ADM mass and positivity theorems - In a system with infinite branes, we may want to generalize the ADM mass to a quantity that measures the mass density, as opposed to the total (divergent) mass. This is probably behind the letters Y-ADM. The ADM mass usually assumes a Killing vector - d_a v_b + d_b v_a = 0. In the Y-ADM business, they generalize the vector v_a - which is a one-form - into a p-form, but otherwise keep the equation to be "ab-symmetrization of the derivative of the p-form vanishes". They discuss how the positive energy theorem generalizes in this case, which may be interesting.

Sergio Ferrara et al. write about gauging an abelian algebra in supergravity.

  • http://www.arxiv.org/abs/hep-th/0410290 - Special quaternionic manifolds - They start with the fact that the moduli space of type II compactifications on Calabi-Yau have the structure of a special quaternionic, times a special Kähler manifold. Because it is always natural for special quaternionic manifolds to make a certain algebra a gauge symmetry, they study the geometrical conditions when it's possible to do so. I suppose that the actual stringy compactifications with fluxes have the property that this algebra is gauged, and this algebra has the interpretation of shifts of the RR-fields, or something like that.

Something about mirror symmetry for supermanifolds.

  • http://arxiv.org/abs/hep-th/0410291 - Toric CY supermanifolds - When they apply the mirror symmetry manipulations to certain supermanifolds (Sethi; A. Schwartz; Aganagič and Vafa) - fermionic extensions of complex weighted projective spaces - they find a relation between the super Calabi-Yau constraint on the A-model side, and the homogeneity condition on the B-side, plus some quantitative relations.

We want more topological string theory!

  • http://www.arxiv.org/abs/hep-th/0410292 - Self-dual YM theory - The author proposes new thick, fattened manifolds, those that suffer from obesity, as the target space for the B-model in order to describe the self-dual part of the N=4 Yang-Mills theory in d=4 in a twistor-like language. This guy obviously knows many things about the subject, more than me, and moreover I don't quite understand what the rules of the game are. Is it just about finding some quantities that resemble the bosonic part of the self-dual part of the YM theory? He is doing Penrose-Ward transforms - is it something that can always be done, or is there some non-trivial restriction?

Now a K-theory for D-branes paper.

  • http://www.arxiv.org/abs/hep-th/0410293 - S-duality for K-theory - The authors (Igor Kříž sounds like a Czech name, and I should know him) study K-theory for type IIB in a B-field background. K-theory is not invariant under S-duality of type IIB. Well, I think it never will because K-theory is just a language to describe the specific objects that can be classically obtained from spacetime filling D-branes - i.e. objects whose tension scales like 1/g. The authors show that indeed, one can't make K-theory S-dual, even if he generalizes twisted K-theory into generalized biased genetically modified twisted K-theory. Well, the full generalization of K-theory invariant under all dualities knows, in a sense, about the whole "theory of everything", and I always found K-theory as a limited description that is very relevant for a few great special examples mostly due to Sen, but otherwise K-theory was a part of the abstract nonsense that tries to propagate into physics.

Now a PhD thesis.

  • http://www.arxiv.org/abs/hep-th/0410294 - Black hole production - That's a massive, 300-page text about black hole pair production in 3, 4, and higher dimensions, with solutions, different types of the instantons signalling the instability, causal structure of the solutions, including the addition of dilaton couplings, electric charges, and angular momentum. A rather impressive work, although I guess that it is more or less a review of existing literature on the subject.

Black hole production is cool. What about another paper on black hole production?

  • http://www.arxiv.org/abs/hep-th/0410295 - Multiple black holes from trans-Planckian collisions - Well, we can feel suspicious about the calculational machinery - the black holes are treated as elementary particles (which may or may not be a fine approach to reproduce the results from quantum gravity) - nevertheless the result, that is meant to kill a previous result, sounds pretty plausible. The production of many black holes is suppressed which means, I hope, that the production of a single black hole is preferred. I am not sure whether we should trust the power laws (the dependence on the energy). Also, it seems as an unnecessary restriction that the author focused on d=4 black holes only. Could not he make the analysis for all dimensions simultaneously?

The last paper must be about twistors...

  • http://www.arxiv.org/abs/hep-th/0410296 - Niels Bohr, Lance Dixon et al. - The authors investigate the arguments of Cachazo, Svrček, and Witten, for the holomorphic anomaly affecting the unitary cuts of one-loop amplitudes. The present authors reduce the supersymmetry from N=4 to N=1, which also reduces the direct connections to string theory and topological string theory (and frankly, also my interest in this calculation). Their results are positive - the results match what you expect from collinearity in the twistor space, even though I don't exactly know what the rules of the game are for the twistors describing the N=1 theories. Most likely, it does not matter.