Wednesday, November 30, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Great Chinese Firewall

Hui Chen helps us - and our Chinese friends - to circumvent the so-called Great Chinese Firewall. If you've ever heard someone in the People's Republic of China who had problems with the access to this blog, you may write her or him the following URL of the mirror.

Right now, the Reference Frame has absolutely no intent to influence the social or political atmosphere in the world's most populous country which is our Chinese friends' internal affair. We assure all the glorious leaders that they have no reason to be afraid of anything. Greetings from the People's Republic of Cambridge, LM

Closed string vacuum solved analytically

The most interesting paper on the arXiv today is a paper by

who is currently at CERN, Switzerland. Around 1998, Ashoke Sen conjectured that the open string tachyon may get a vev that corresponds to a complete annihilation of the D-brane onto which the open strings were attached. This predicts the energy density of this minimum of the tachyonic potential: it must be equal to minus the tension of the D-brane that has annihilated.

In the framework of boundary string field theory (BSFT), this fact has been proved by Kutasov, Marino, and Moore. Of course, there have always been almost complete physical arguments that assured us that no reasonable person had any serious doubts that Sen's conjecture - the second insight in science after the Higgs mechanism that shows that the tachyons are more than just an inconsistency - was correct.

The formalism of Witten's cubic string field theory of the Chern-Simons type is however much more well-defined than boundary string field theory. People wanted to verify Sen's conjecture in this cubic string field theory, too. They could have done so numerically and they obtained 99.9999% of the right value. Many other facts have been checked numerically, too. Many physicists also proposed various formal heuristic solutions and maps between the cubic string field theory and the boundary string field theory but it was usually hard to give these formulae a precise meaning.

Blackberry loses round in patent dispute

News: Mike Lazaridis, the founder of the Perimeter Institute and the company Research in Motion - that produces the e-mail mobile gadgets called BlackBerries - loses round in a patent dispute.

Colbert report with Brian Greene

It's definitely intense fun and Brian Greene is doing a superb job.

Thanks to Joe Minahan for the tip. Colbert's show is somewhat similar to Bill O'Reilly's Factor, indeed. I was explained that it is a deliberate similarity.

Just like the Reference Frame argues that string theory is forced upon us by mother Nature in somewhat analogous way as the evolutionary framework in biology, and much like Peter Woit believes that string theory is just like Intelligent Design, Colbert says that Occam's Razor requires us to accept the simplest explanations of everything - and the simplest explanation of the real world is that it was created by God like that: click. Occam's razor proves that Intelligent Design is better than science.

That's slightly paradoxical because Stephen Colbert is the youngest among 11 children, and is therefore a walking experimental proof of M-theory: he's the M-theoretical circle at weak coupling, in fact.

Two proofs of global warming



(Via Grugoš Jotl.)



That should be enough to neutralize the heretics.

Computation after 90th birthday

We just had a dinner to celebrate the Loeb lecturer, John Hopfield from Princeton, who bravely applies physical reasoning to neural networks and other models of the human brain.

There have been many interesting discussions during the dinner but I will only mention a couple of them. Howard Georgi allowed me to understand a bit better the pretty high score of our F-group in the last homework problem set assigned in my class. Thanks, Howard, for the help. ;-) Yes, F stands for "female". Two different homework assignments have been made for the two groups, and no one has yet called the New York Times, not even Howard himself. ;-)

Incidentally, my feeling after the class in the morning was that 160 minutes is simply too little to properly teach scattering, partial wave analysis including all of its limiting cases, Born approximation, including all the kinematical relations between amplitudes, cross sections, transition rates, time-dependent perturbation theory, and examples including the Yukawa and Coulomb potentials, spherical well, and 38 other issues. Moreover, these calculations in the old-fashioned quantum mechanics are sometimes even messier than in quantum field theory. I would probably reduce the amount of material related to these questions in the syllabus.

Tai Wu, a member of our band, joined my opinions about the Summers controversy and Noam Chomsky and other things. We chatted about the LHC, too. And no, C.S. Wu did not belong to his family.

Ursula Holliger (harp) described many things including the music critics. Of course, they're often annoying and they became critics because they could not become the musicians. Not surprisingly, the very same thing probably holds for the literary critics and the physics critics, too. ;-)

Chris Stubbs has finished reading Barton Zwiebach's book on string theory. Because he learned many things and was pleasantly surprised that the whole modern high energy theoretical physics is fully accessible to him, he actually thinks that every experimental physicist should learn string theory from this book. I am happy to report this experimental conclusion. :-)

Incidentally, Chu Xing who works in a factory in Hong Kong also studies Barton's book. Sometimes, he would find it helpful to know the answers to Barton's problems in the book; he informed me in the e-mail. When I had the pleasure to talk to Dr. Simon Capelin who may be credited for having published so many great physics books in the Cambridge University Press today in the afternoon, he agreed that Chu Xing should get the password to access the web page of Barton's book at the CUP's server. We will see this week whether Barton will agree. ;-) Good luck, Chu.

One of the crimes against the copyright (not humankind) I did in 1993 was to ask a librarian in Prague to xerox the superstring textbook by Green, Schwarz, and Witten for me. She did so! For 12 years, I could not sleep because I worried that the Cambridge University Press would eventually sue me. It turned out today that Dr. Capelin who published the book will probably forgive me this particular sin!

Norman Ramsey has told me many stories about the history of physics, his lectures on 9/11/2001 (the day of my PhD defense), the development of atomic clocks, negative temperatures of lasers, the most precise current experiments testing both special and general relativity, and his recent studies of string theory. He believes that the vacuum energy is gonna be an important question in physics for the years to come. Another very illuminating comment from him was about the changes of your approach to research when you're older than 90 years. Of course, when you're above 90, almost everything works easier than before. Just the short-term memory is slightly worse. When you need to finish some integral - that you otherwise do on the top of your head - with your calculator, it is sometimes a bit more difficult to remember what you want to type on your calculator. It is slightly more difficult than when you are young, e.g. about 85 years or so.

Well, what an impressive person. ;-)

In the afternoon, James Wells (Michigan) was explaining his children GUT constructions extending NMSSM but I will only mention the talk if I have really too much time tomorrow which is unlikely.

Monday, November 28, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Royal society: ban science on the web

The Royal Society - i.e. the British Academy of Sciences - has warned that "making research freely available on the internet could harm the scientific debate". It could even lower the profits of printed journals, the society predicts, especially of the non-profit journals. :-) The Royal Society is fully committed to the preservation of the reptiles.

A free access to scientific results on the internet could also threaten feudalism itself and the leading role of the royal family in the world. Instead, the internet may encourage heretics. Prince Charles agrees that science and technology are dangerous. He expressed concern that economic progress is "upsetting the whole balance of nature." In another interview, he said that "if you make everything over efficient, you suck out, it seems to me, every last drop of what, up to now, has been known as culture."

Don Page & death of de Sitter

A. V. Yurov and his mirror image, V. A. Yurov have a very provocative paper attempting to reconcile the conjectured lifetime of the KKLT de Sitter vacua calculated from the low-energy effective field theory - this lifetime is not too far from the recurrence time and let's call it a "googolplex" - with the much shorter lifetime of our Universe comparable to a mere "googol" that was recently advocated by Don Page and his even more provocative paper. ;-)

Let me emphasize at the beginning that although I find the KKLT estimates somewhat uncertain, they are definitely much less speculative than anything I am gonna describe in this text.

Don Page argues that if our Universe approaches the de Sitter exponential cosmological expansion with the currently likely value of the vacuum energy, then its lifetime should be shorter than 10^{50} years or so. Why? Because if the lifetime were longer, then - I kid you not - most of our perceptions (such as the feelings of our brains expressed by a complicated projection operator onto a state of your brain) would usually occur because of random vacuum fluctuations.

Sunday, November 27, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Discrete physics

One of the "great" ideas that are being proposed billions of times every day is the idea that the fundamental physical laws of Nature are "discrete". The world is resembling a binary computer - or at least a quantum computer, we're being told very often. "Discrete physics" even has its own USENET newsgroup "sci.physics.discrete" which has fortunately been completely silent since it was created. Various games and "types of atoms" that are supposed to produce spacetime at the Planck scale are even sold as "alternatives to string theory".

I am among those who are convinced that every single proposal based on the idea that "the fundamental entities must be discrete" has so far transparently been a crackpot fantasy. What's wrong with all of them?

Both discrete and continuous mathematics matter

First of all, both discrete as well as continuous mathematical structures are important for actual reasoning and calculations in physics and not only in physics. We just need both of these categories of tools and theorems. Many people who like to say that only one of them may be fundamental are usually the people who don't know the other set of insights well enough - or they don't know it all. And they don't want to learn it. Instead, they want to promote a "theory" that implies that it is good if you don't learn it. In other words, they ignore at least one half of the basic math that is needed for physics.

Saturday, November 26, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Holographic 300 GB disks

What is the capacity of optical disks? If they're DVDs, you can squeeze up to 4.7 GB of information on them. Imagine a very similar disk with 300 GB on it. Yes, it is more than the magnetic hard disks you have ever seen.

Amazingly enough, some readers found the opportunity to argue about the previous sentence to be more interesting than the new fascinating technology described below - very sad.

And it would read the information 10 times as fast as the DVDs. Impossible? No!

has developed a commercially acceptable version of the holographic disks. It could be sold as early as in 2006. The required physics was discovered by Dennis Gabor in the 1950s using the methods of anticipation plagiarism. More concretely, Gabor stole the insights about the holographic principle in quantum gravity from 't Hooft and Susskind and applied them in optics 40 years before 't Hooft and Susskind published it and 60 years before string theory was confirmed experimentally.



Unfortunately, 300 GB is still 50 orders of magnitude less than what the area should be able to store according to the holographic principle ;-), but it is progress nevertheless. See other articles via news.google.com or the company's web. If you're interested, you should certainly see the WMV video or another exciting QuickTime video.

PDF introductions:

Paradoxically, the holographic disks are the first ones in which not only the two-dimensional surface but also the three-dimensional bulk of the medium is used. One can record thousands of holograms on the same medium by changing the angles or frequencies. Many bits are read simultaneously. The hologram is written down by adjusting many bits in a semi-transparent two-dimensional "checkerboard" which is really called "spatial light modulator" or LSM (also known as the "linear sigma-model") and letting two parts of a split laser beam to interfere with each other to create a three-dimensional pattern within the optically sensitive plastic medium. The LSM does not differ much from some modern types of displays.

When you read the data, you only use the reference beam that deflects off the medium and reconstructs a similar checkerboard image in a "detector".

The disks are slightly thicker than the DVDs but have the same area. The optimists predict that these disks could eventually store up to 1,600 gigabytes of data that could be read as quickly as 15 megabytes per second. Of course, technology will only be pushed to the limits if the modest versions of the disk turn out to be reliable.

Although the idea of the holographic storage disks has been around since 1963, people could not find a good enough medium for 40 years. The two-chemistry "TapestryTM" disks have suddenly solved these problems. The lesson - one that even the string theorists should learn - is that even if you have a great idea deeply connected with an obviously important physical principle such as holography, it may take 40 years - years of listening to obnoxious Peterwoits - before the details are refined so that you may celebrate the final success. Fourty years? String theory was born in 1968. You can do the math.

Incidentally, the readers who think that this posting - about a fascinating technology that has become a reality - should ignite discussions about the capacity of conventional magnetic hard disks are considered to be retarded and uncultural intellectual equivalents of dogs by The Reference Frame. But feel free to write whatever you want.

Haf haf. (That was in the Czech dogs' language. Not sure how the American dogs translate it.)

Friday, November 25, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Supernovae: Lambda is constant

Scientific American reports that the observations of 71 distant galaxies suggest that the dark energy is constant, namely the cosmological constant, indeed. The upper bound on the pressure/energy_density ratio is now

  • pressure/energy_density < -0.85,

very close to "-1". More details in the paper by Ray Carlberg et al.

ATLAS at Wikipedia

Incidentally, if you look at Wikipedia today, the featured article is about the

It was mostly written by SCZenz, a graduate student of experimental particle physics at Berkeley. Very good job!

Ignorance of Paul Boutin

In this text, I want to demonstrate that Paul Boutin has no idea what he is talking about in his text at Slate - he is writing about theoretical physics - and why he is an example of people who know absolutely nothing but who want to influence absolutely everything.

  • Elegance is a term theorists apply to formulas, like E=mc2, which are simple and symmetrical yet have great scope and power.

This is one of the less serious problems in his article, but I don't think that any physicist would use the equation "E=mc2", popular among the laymen, as an example of an elegant piece of mathematics or physics. Incidentally, in this form, the equation has never appeared in Einstein's revolutionary papers.

  • The concept has become so associated with string theory that Nova's three-hour 2003 series on the topic was titled The Elegant Universe (you can watch the whole thing online for free here).

NOVA's "The Elegant Universe" was titled this way not because NOVA was the first one to realize that string theory is elegant, but simply because the title was borrowed from Brian Greene's bestseller - a book version of the TV program - that every journalist who is informed about modern physics knows very well. This book is the reason why the words "elegant" and "string theory" simultaneously appear at so many pages.

  • That's because compared to E=mc2, string theory equations look like spaghetti.

At the beginning of the show, Brian Greene reminded us that it may be rather difficult to explain general relativity to dogs, and therefore even the people may have problems to understand advanced mathematical concepts that are necessary to understand string theory and its beauty.

No doubt, people whose mathematical skills end with the product of "m" and "c2" - and who are therefore probably closer to the dogs than to Edward Witten - will hardly appreciate algebraic geometry, mirror symmetry, conformal field theory, or homology of the super moduli spaces. After all, dogs don't distinguish superstrings and spaghetti either.

  • His General Theory of Relativity says gravity is caused by the warping of space due to the presence of matter. In 1905, this seemed like opium-smoking nonsense.

Except that general relativity was published in 1915, not 1905. I would think that such flagrant ignorance of history of science should prevent one from finishing the high school. In reality, it is not even a problem for publishing physics articles at Slate.

Moreover, relativity - either special or general - never seemed like opium-smoking nonsense to the physicists. The special theory of relativity was accepted almost instantly; the general theory of relativity was accepted quickly - and almost universally after the 1919 observations of the bending of light. There may have been counterparts of Paul Boutin who always thought that relativity was opium-smoking nonsense but their voice never played any role in physics.

Except that the uncertainty principle is not an equation. It is an inequality and not a particularly elegant one.

  • The closest you can get is a function related to Planck's constant (h), the theoretical minimum unit to which the universe can be quantized.

A "function" cannot be related to Planck's constant. And Planck's constant is not a unit into which the universe can be quantized. It is a quantum of the action or the angular momentum, not a "quantum of the universe".

  • If relativity and quantum mechanics are both correct, they should work in agreement to model the Big Bang, the point 14 billion years ago at which the universe was at the same time supermassive (where relativity works) and supersmall (where quantum math holds). Instead, the math breaks down. Einstein spent his last three decades unsuccessfully seeking a formula to reconcile it all—a Theory of Everything.

Einstein never worked on reconciling quantum mechanics with relativity. What he worked on was unification of electromagnetism and gravity but he never intended quantum mechanics to be a part of his fundamental equations.

  • The most popular string models require 10 or 11 dimensions.

They're not the most "popular" ones. They're the only ones that predict a stable universe with all the qualitative features we observe in the real world.

  • Krauss' book is subtitled The Mysterious Allure of Extra Dimensions as a polite way of saying String Theory Is for Suckers.

Well, I hope that it will be widely understood that my comment that Boutin's intelligence resembles that of dogs will be viewed as an appropriate answer to this "gentle" man.

  • Scientific Method 101 says that if you can't run a test that might disprove your theory, you can't claim it as fact.

If you can run a test that might disprove your theory, you can't claim the theory as fact either. And if your experiment actually disproves your theory, you definitely cannot claim the theory as fact. ;-)

  • And there's no way to prove them wrong in our lifetime.

Maybe. The same thing holds for the evolution etc. But there is a significant chance that the theory will be proved right - a deeper theory than the previous ones to describe reality - in our lifetime. Mr. Boutin does not seem to be interested in this alternative possibility that string theory is right; a textbook example of Crackpotism 101.

  • Einstein's theories paved the way for nuclear power.

The only thing that Einstein's theories had to do with nuclear power is that he could have calculated the gained energy from the mass differences of the nuclei - much like he could have done for any physical process in the world. The development of science and technology behind the nuclear power has nothing to do with Einstein's theories. Einstein's letter to Roosevelt (warning him that the Nazis may have been working on the bomb) is perhaps the only link between Einstein and the nuclear energy.

  • Hiding in the Mirror does a much better job of explaining string theory than discrediting it.

Good joke.

  • Krauss knows he's right, but every time he comes close to the kill he stops to make nice with his colleagues.

He knows that he's right much like the Catholic Church who opposed Darwin's theory, does not he? A difference between string theory and its Kraussian "alternatives" is that the former is evaluated by scientific, rational arguments and calculations. The latter is evaluated by articles written by journalists whose understanding of physics resembles the skills of dogs.

It's pretty sad if someone like Boutin whose knowledge of modern science is completely superficial - and he just writes down confused misinterpretations of some popular accounts of physics that have already been written in such an oversimplified way to target the silliest 10% of the population - are given space at such influential places as Slate.

Well, of course I know why he was given space. It's because he's the senior editor at many places like that. ;-) Unfortunately, even having a lot of money does not prevent one from being a complete ignorant.

Harvard diversity skyrockets

There are people who still think that Harvard is not diverse enough. Well, that's certainly wrong. Harvard tops the black student yield among 22 colleges in an ensemble. The female tenure offers have essentially doubled and exceeded the level before Summers' presidency.

On the other hand, Princeton is different. While it seems that the women are already allowed to enter the physics department, it was not the case 50 years ago because they were a "distraction" for the Princeton scholars. At that time, women were already walking to the left and to the right everywhere at Harvard!

Thursday, November 24, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Annihilating letters



If you're just waiting for your turkey, you can try to destroy some pairs of letters.

Wednesday, November 23, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Physics fades from UK classrooms

Quite independently, Clifford discusses the very same issue - physics at British schools.

2005 is the international year of physics, so let me offer you some "optimistic" news - namely news about the intellectually degenerating British society.

The number of British pupils who took physics dropped by 40 percent in the last 20 years. In the last 10 years, the number of UK physics departments dropped by 30 percent. And the situation will become even worse as the current generation of teachers will retire and be replaced by mostly female young teachers who usually don't like physics, Alexandra Blair predicts in The Times.

RealClimate loses

Thanks God, RealClimate.ORG, the propagandistic blog designed to politicize science, a kind of blog that refers to all politically inconvenient scientific results as the "industry-funded misinformation" (which is always banned on their website) lost in both categories of the Deutsche Welle International Weblog Awards 2005, despite their shameless self-promotion and their attempts to increase the number of votes in unfair ways - so similar to their "scientific" methods. And despite the fact that the competing blogs are composed of a much smaller number of authors than RealClimate's "hockey team" of eleven authors.

When I say that they label all politically inconvenient scientific results as "industry-funded misinformation", what I have in mind are these 38 hits on their website. As Joseph Goebbels said, a lie that is repeated 38 times becomes the truth. Imagine that in spite of this river of naive political articles about funding by the "evil" industry that make Fidel Castro look like a moderate conservative in comparison, they define the goal of realclimate.org on their title page as follows:

  • ... The discussion here is restricted to scientific topics and will not get involved in any political or economic implications of the science. ...

Haha. Very funny. If climate science were funded by serious industry instead of mostly corrupt left-wing foundations, these guys would be begging on the street.

Tuesday, November 22, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

How they stole $2800 from my account (for a while)

One month ago or so, I did a very stupid thing. A few hours after I wrote one of my reviews at amazon.com, I received an e-mail inviting me to

(looks good, does not it?) and asking me to update my debit card number and so on to improve the community and so forth. Convinced that it had to be related to the review - that is only posted quickly if amazon.com recognizes your "real name" through your payment card - I did not hesitate and decided to get rid of the paperwork as soon as possible and defend my priviliged status at amazon.com. Of course, I am getting roughly 5 phishing e-mails per day but this one was special: it got me. ;-)



After opening a page that looked just like at amazon.com, I entered my credit card number to the fraudulent website, and to show how really stupid I was, I also filled out another page with the social security number. (Please don't annoy me much with the messages about the credit history. I don't intend to borrow anything and I don't care.) Incidentally, the server was located in Thailand, not China, where the page was redirected through Germany. It was very easy to find out many other details about the website one month ago.

Monday, November 21, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Scholars at risk

If you know about a scholar who is prosecuted or discriminated in her or his country, you may want to remind me about the scholar so that I would nominate her or him for Lawrence Summers' "Scholars at Risk" fellowship.

CERN receives supercomputing award

The European Center for Nuclear Research (CERN) is the place where the World Wide Web was developed. Even the uncultural people who don't care about the existence of the Higgs boson or the superpartners may have noticed one of the by-products of high-energy experimental physics, namely the web.

Despite some rumors, Al Gore did not invent the web. The only discovery in computer science that Al Gore has made are algorithms. :-) Despite the contributions of the unsuccessful 2000 presidential candidate to computer science, you should keep in mind that most websites start with Dubya Dubya Dubya.

The Large Hadron Collider should start operations in 2007 and it will require many gradual technological advances to occur. Look at this article:

In this article, you can remind yourself about the immense amount of data that CERN will generate and that will have to be analyzed. Even if the people do not care about particle physics, experiments like the LHC represent a very natural playground to improve technology - such as grid computing - that can become useful in many other contexts in the future. Of course, these results are not the goal of particle physics but rather a by-product; but they are another reason why people may find investments to pure science - and high energy physics in particular - to be a good idea.

Quasinormal contours

Songbai Chen and Jiliang Jing calculate a formula that is perhaps the single most general existing generalization of our formula with Andy Neitzke describing the asymptotic, highly-damped scalar quasinormal modes of the Reissner-Nordström black hole. Their setup involves a scalar field coupled to the Gibbons-Maeda dilaton spacetime with a general coupling.

The contours in the monodromy method immitate our contours in the Reissner-Nordström case. Also their result is similar and it involves the exponentials that depend both on the Hawking temperature as well as the temperature of the inner horizon. In their case, there is also an additional square-root dependence on the coupling "xi" of the scalar. This dependence is another piece in (already) overwhelming evidence that "log(3)" is not universal but depends on many couplings and other details. An entertaining feature is that the Reissner-Nordström result is reproduced for "xi=91/18".

I am actually a bit confused by this number. Don't you reproduce the same result for "xi=-5/18", among many other choices? Why is it exactly "91/18" that was chosen?

More generally, I am still convinced that a future understanding of general relativity and physics of black holes and horizons, including thermodynamics and the (absence of) the information loss paradoxes will involve much more complexification, analytical continuation, and computations in unphysical regions of the parameter space than the current descriptions. The continuation of physics into complex (and other unphysical) values of the parameters (such as the spacetime coordinates) is relevant and legitimate in quantum gravity much like it is relevant in quantum field theory. However, in the case of quantum gravity, there are many ways how the continuation may be done and there are many subtleties that one must be careful about. In my opinion, it means that analytical continuation will be an even more important and bulky portion of our future understanding of quantum gravity than the role they play in quantum field theory. Although these particular quasinormal calculations only depend on the low-energy effective action, I may imagine that various sophisticated and diverse ways to analytically continue physics to unconventional regions of the parameter space may become important for string theory itself.

Saturday, November 19, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Non-Kähler compactifications

Li-Sheng Tseng from University of Utah gave a Duality Seminar about

  • Flux Compactifications and Moduli

The talk focused on non-Kähler compactifications with fluxes which is a very interesting topic that however remains controversial. Let me try to explain why.

For the sake of simplicity, Li-Sheng discussed the case of a non-zero H-field only; other fluxes are set to zero. The condition of unbroken supersymmetry implies that the three-form H must actually be expressed in terms of a derivative of the differential two-form that gives you a Hermitean metric. Why? Recall that the H-field enters as a kind of torsion to the overall connection - and a spinor should be covariantly constant under this connection.

Because this exterior derivative of the metric is not zero, you can't really call it a Kähler form. And you can't call the manifold a Kähler manifold either. However, when we deal with heterotic string theory, there is also the usual Bianchi identity for H

  • dH = alpha' Tr (R /\ R - F /\ F)

When we consider the classical compactifications with "H=0", we relate the curvature of the geometry "R" and the curvature of the gauge bundle "F". For example, we can cancel them trivially by embedding the spin connection to the gauge connection - but that's definitely not the most general solution. Both connections are nevertheless of the same order. The size of the manifold is not determined. The Kähler moduli are not fixed and "alpha'/a^2" is a good expansion parameter.

That's both a good news as well as bad news. It is good news because reliable calculations can be done even perturbatively. It is bad news because the moduli are not stabilized which disagrees with basic properties of the real world around us, among many other worlds.

However, when we choose a non-zero value of "H", the equation above makes it clear that terms with different powers of alpha' are getting mixed. Another equation tells you that "H" and the metric are of the same order, and therefore you can't assign unique powers of alpha' to all your fields; dimensional analysis breaks down. This implies that the size of the manifold is comparable to the string length (i.e. "of order one") if the equations are to be solved. For a finite value of the fluxes, the expansion in "alpha'/a^2" is strongly coupled. Li-Sheng actually argued that this conclusion is only correct for a T2-fiber in his main example while the K3-base may be arbitrarily large. But at any rate, there are some dimensions whose size is stringy which forces us to include infinitely many terms at all orders in alpha'. Any truncation seems unreliable.

While the Hermitean metric is not a closed form, its square continues to be co-closed, and Li-Sheng told us about some examples of generalized geometry - conformal Calabi-Yau geometry, for example. These are nice abstract notions, ideas, and formulae, but the question whether an actual CFT that describes such a perturbative string theory exists remains unanswered. No such a CFT has been explicitly found - and not even proved by an existence theorem. Unlike the Calabi-Yau case, no explicit orbifold point in the moduli space is known either. At the level of geometry only, the existence of some particular examples has been shown, but I doubt that these proofs exceed some low-energy geometric approximations and imply the existence of the full backgrounds of string theory.

Note that you must solve the equations for "H"; Einstein's equations with the appropriate right-hand side; and it turns out that the dilaton is non-trivial which also forces you to solve a non-trivial Laplace-like equation for the dilaton.

All of these equations are pretty hard to satisfy. A proof that such a combined solution for all these fields exists amounts to a rather extensive generalization of Yau's theorem (such a description is especially appropriate for the metric and its Einstein's equations with a source). There are some details that seem hard and potentially incompatible with the perturbative approach to the question. For example, a static dilaton must satisfy something like

  • nabla^2 (exp(-phi)) = F^2 + H^2 + ...

whose right-hand side actually turns out to be positively definite at the leading order. This would prevent the dilaton from being smooth but non-constant everywhere, as required in Li-Sheng's construction: the Laplacian has opposite signs at the maxima and minima of the dilaton. However, he argues that the higher-order terms in alpha' appear in the equation above and these extra terms may be negative and compensate the leading-order positive terms.

Quite generally, I remain skeptical about the constructions that seem impossible or inconsistent at a leading order in a certain perturbative expansion and whose consistency is being explained by a mere existence of some higher-order (or even non-perturbative) terms. Don't get me wrong: constructions that are not accessible perturbatively are all but guaranteed to be important in many situations. All moduli in the real world are stabilized, for example, which makes any expansion about their extreme values problematic.

Even though the backgrounds that do not solve the equations of motion order by order in a certain perturbative expansion are important and will be important, the importance does not prove that they actually exist. Cancelling a first-order problem by pointing out a possible second-order cure may be a hint that a consistent theory exists - but it is definitely not a proof. If we cancel terms with a different parametric dependence on any parameter G, it certainly means that the perturbative expansion in G breaks down. That is not enough to prove that the theory is doomed, but it is not enough to prove that it is consistent either.

For example, the second-order terms may be negative but the third-order terms could be positive and such that the sum of the first three corrections remains positively definite. Is it up to the collective decision of the terms at all orders whether the qualitative conclusion based on the first-order approximation (the theory does not exist) is correct; or whether the conclusion based on the second-order approximation (the theory does exist) is right.

Note that the existence of simpler vacua in string theory has been firmly established. In my opinion, the people thinking about the non-Kähler issues may want to focus on proving the existence of their conjectured generalized theories - for example the existence of CFTs in the cases in which the dilaton may be kept near minus infinity. When the perturbative expansions break down, it is only the exact result that is relevant. One should try to decide whether a truncation of some expansions leads to qualitatively correct results. And the answer can be either Yes or No.

Friday, November 18, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Elsevier Science and crackpots

W.S. has pointed out an article written by someone called Ms. Liisa Antilla that has been accepted into a peer-reviewed journal "Global Environmental Change Part A" published by Elsevier Science - the publisher that has done a lot of good things for high-energy physics in the past but whose journal "Nuclear Physics B" is widely considered to be a dinosaur that should die soon, especially because the journal seems much more expensive than what is appropriate in the era of the internet (and the arXiv).

Incidentally, if your university does not provide you with access to the article, you can buy the text for $30.

W.S. is amazed by the article, I am also amazed, virtually everyone else is amazed. Why are we so shocked? The title of the article is

  • Climate of scepticism: US newspaper coverage of the science of climate change
and it is arguably the first published peer-reviewed article in the world whose main point is to accuse dozens of particular scientists from scientific misconduct and corruption just because the result of their research does not agree with the author's silly ideological fantasies, without having the tiniest glimpse of evidence. What do I mean? Who is the author? What is it all about?

First of all, Lisa Antilla is not a scientist according to all available data. Already the abstract makes you sure that you should not expect the scientific method to play any role in what follows:
  • This two-part study integrates a quantitative review of one year of US newspaper coverage of climate science with a qualitative, comparative analysis of media-created themes and frames using a social constructivist approach. ...
Well, a "social constructivist approach" is one of the postmodern "approaches" whose irrational character - and absurdity - was pointed out by Alan Sokal. The 15 pages make it absolutely clear that Liisa Antilla has no idea about the subject she is writing about - the climate in this case - and her ability to have learned the English alphabet is demonstrably her greatest intellectual achievement.

At any rate, this achievement apparently seems sufficient to get published in peer-reviewed journals that belong to Elsevier Science.

It must be clear to any rationally thinking person that the chance that an article about "warming" gets published in the newspapers today is at least 5 times higher than the probability that an article that implies "no warming" or "cooling", even locally, gets published - even though cooling and warming are essentially in balance. Bias of one order of magnitude is apparently not high enough to satisfy Liisa Antilla who argues that every article that does not support the crackpot idea of a looming global warming catastrophe must be an artifact of corruption.

Seed magazine

Seed magazine seems really serious about creating a highly stimulating environment for important scientific ideas. Their five categories in the front of our minds are

  • Einstein
  • Evolution
  • Genetics
  • Science/Religion
  • String Theory
That's a pretty exciting mixture of topics and many people may have a lot of fun when Seed magazine really starts.

Nima at Radcliffe

Melanie Becker organizes nice lectures at the Radcliffe Institute, formerly known as Harvard University for girls. The first lecture was by Cumrun Vafa - about the Swampland, and two talks by Nima Arkani-Hamed followed. Today, he described our project (with Cumrun Vafa, me, and Alberto Nicolis) involving the "weak gravity" constraints. In my opinion, he did a terrific job. Let me only summarize a few slogans:

  • in quantum gravity i.e. string theory, one should have no global continuous symmetries; it is known in string theory that a symmetry current, a (1,0) or (0,1) tensor, is associated with any symmetry, and it can be multiplied by "del X" or "delBAR X" to create a (1,1) marginal vertex operator for a gauge boson, proving that the symmetry is local after all
  • this constraint looks too fragile because one can immitate global symmetries by weak symmetries with a very small coupling constant which seem allowed
  • therefore, it would be more natural if very weak couplings were forbidden, too
  • more precisely, if a U(1) gauge group has too small a coupling, ...

This posting was never finished. Read the preprint hep-th/0601001.

Congratulations to Devin Walker

Clifford Johnson at CosmicVariance was thrilled when he learned that he belongs among my favorite people. So let me generate a new thrill. I like Devin Walker, much like many other people like him. We widely expect that tomorrow, he will become the first US-born and US-educated African American to earn a PhD degree from the physics department at Harvard. So let me say in a preliminary fashion: Congratulations, Devin!

Note added later: We had some sparkling wine and cakes. Melissa Franklin, who was on the committee, said "Welcome to the 20th century, Harvard". Of course, the celebration is a fun event with a lot of people attending.

Thursday, November 17, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Sixteen years after Velvet Revolution

Sixteen years ago, on November 17th, 1989, students in Prague commemorated the 50th anniversary of the closure of the Czech universities by the Nazis back in 1939. On November 17th, 1939, nine students were executed. This time, back in 1989, the students were beaten up not by the Nazis but by the communists.

Together with Tuesday 9/11/2001, the dates around the Velvet Revolution are the only days in my life that I remember very clearly. On Friday evening, November 17th, 1989, the news about the student demonstration circulated among everyone who was interested in politics. The Radio Free Europe and other "anti-socialist" radio stations of course played a very important role in informing (and provoking) the public.



There were rumors that a student, namely Martin Šmíd, was killed. (Another student, Mr. Růžička, who was thought to be dead actually turned out to be Mr. Zifčák, an agent of the secret communist agency, but I never understood what this whole story was all about. As far as I can say, the story was irrelevant.) Actually many years later, we had many published debates with the very same Martin Šmíd about astrology which he believes (and I don't). At any rate, the rumor was definitely false and Martin Šmíd was not killed by the communists.

Tuesday, November 15, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

A Hagedorn alternative to inflation?

Robert Brandenberger, Ali Nayeri, and Cumrun Vafa argue that a stringy phase of cosmology dominated by strings near the Hagedorn temperature is an alternative to inflation.

More precisely, their calculation suggests that one can obtain a scale-invariant spectrum by assuming that the temperature was near the Hagedorn temperature in the past - and the environment was dominated by a long, strongly excited string. Moreover, the amplitude of fluctuations from the scale-invariant spectrum is suppressed by the fraction "(l_{Planck} / l_{string})^4", and this insight implies a consistent picture for "l_{string}" being roughly 1,000 times longer than "l_{Planck}", with "g_{string}" being the inverse quantity 0.001.

That's an exciting statement. You can have two possible negative reactions; it is either wrong or equivalent to inflation (much like the good features of the ekpyrotic Universe may be argued to be equivalent to inflation). Assuming that the calculated scale-invariance is correct, which I have only checked partially so far, the second possible answer is pretty interesting. How can this picture be equivalent to inflation? In fact, how is the usual causality argument that implies that the temperature should not be isotropic evaded?

Monday, November 14, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Which way the wind blows

Well, one of the goals of the physics lunch today will be to gauge which way the wind of support blows. Although I may be right-wing, it should not be surprising that my wind blows to the left-hand side (with the usual acronym for the left-hand side) - of course, nothing against and all my respect for the other side! It seems to me that the left-hand side is also the natural direction in which the physics wind should generally blow - and not only because physics is about thoroughly addressing issues rather than skimming over them. But the wind experiment has yet to be done.

Result: some people - e.g. a person who will have to travel to Scandinavia soon because of a person who had played with explosives - did not even believe the Crimson about the plan of the left-hand side. But everyone agreed that there was no evidence that the leak was deliberate, and the department will decline to support a certain unphysical underground petition designed to criticize the left-hand side using the hypothesis that the leak was deliberate. (I would personally find nothing wrong even about a deliberate leak because it is a natural preparation for action that should not be a complete shock, but that is a different issue.)

Sunday, November 13, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Weather critical exponents

How quickly is the weather changing? What is the right probabilistic distribution for the apparently random history of temperatures at a given location? Consider the deviation "Delta T(d)" of the daily temperature (on day "d") from the long-term average. Compute the correlation coefficient "C(s)" between "Delta T(d)" and "Delta T(d+s)", two temperature variations separated by "s" days.

Govindan et al. (some of the authors being famous people who promoted fractals) showed in Phys. Rev. Let. (and in a book edited by Murray "SantaFe" Gell-Mann) that there is apparently universal scaling

  • C(s) = #.s^{-gamma}

where the exponent "gamma" seems to be universal, between 0.6 and 0.7, independently of the location (at least as long as it is a continental station). The universal exponent could very well be 0.65. (This counting is somewhat analogous to the CMB scale-invariant spectrum but the exponent differs.) The law seems to hold when "s" is a couple of days or ten years - in fact, no violation of the law is known from the data, not even at very long time scales. This critical exponent is what I call an interesting insight about temperature dynamics.

The authors demonstrate that most climate models give a very different exponent which is usually closer to an experimentally wrong value 0.5, and moreover lead to results that depend on the location: coasts are supposed to differ. Because the results of Govindan et al. imply that the climate models don't work - and moreover, more concretely, overestimate the trends, the consensual scientists such as William immediately know what to think about the paper:

  • But... is [the paper] any good? Weeeeeelllll... probably not. This is yet more of the fitting power laws to things stuff. They use "detrended fluctuation analysis" (DFA) which I don't understand, but that doesn't matter, we'll just read the results.

Of course, the result that William sees at the end of the paper is that the models give wrong exponents and their prediction of global warming is thus unjustified. This could mean that the predicted global warming will be smaller than one predicted by IPCC 2001, and therefore William knows what to think about the paper even though he does not understand a word.

I added the boldface because William's innocently honest description of the "mainstream" climate edition of the "scientific method" is refreshing. William continues with some amount of nonsensical criticism - such as that it is strange that they included Prague as a representative city :-) - and then he promoted a paper by Fraedrich and Blender (FB), also in Phys. Rev. Let.

These Gentlemen offer a surprising conclusion that the scaling exponent should be around 0.5 for inner continents and 1 for the oceans which William, of course, immediately accepts. Why? Because it would help his global warming beliefs.

I have not analyzed the data in detail, but the FB statement seems to contradict something I would call a physics intuition. Oceans or continents can change the (dimensionful) timescales of exponentially decaying processes or the overall size of the temperature fluctuations, but they should not change the (dimensionless) critical exponents of the power laws.

It should not be surprising that the original team, Bunde et al., published a one-page comment also in Phys. Rev. Let. about FB which shows that the FB results contradict both their analysis as well as the initial data. Of course, William won't inform you about such a thing and he will erase every comment on his blog that would try to link to the new corrected paper by Bonde et al. - which is what he did to my comment. He's just damned scared that all these flawed scientific assertions will be revealed.

Instead, he is going to convince you that the critical exponents (and probably also the rest of physics) are uninteresting because they have already validated their friends' models and no amount of heresy such as the critical exponents - or publications in Phys. Rev. Let. that no true AGW believer would ever read - can change the holy word. ;-)

Meanwhile, the people who are still able to use their brains may compute the critical exponents in the statistical climate data and falsify most of the climate models that are being used today. Noise is not always the same thing as another noise, and there are scientific methods to determine whether two "noises" match. Cosmologists have been using these methods for more than a decade to analyze the CMB. The modern alchemists of course don't want to hear about the methods that have the power to show that some models are simply wrong and the "wrongness" can't be hidden behind the apparent "randomness" because when investigated scientifically, "randomness" is not universal. The very purpose of science is to uncover the layer of randomness and see the patterns that can be expressed by quantitatively measurable and predictable numbers.

Finally, there have been quite many different papers that show that the climate models fail to reproduce the observed temperatures, for example paper from Boston University here; or a paper by Douglass et al.

Saturday, November 12, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Cosmic string or dark matter

I just received a mail from Rich Murray who has taken many pictures of the region near CSL-1, the "cosmic string lensing" candidate.

For example, the newest picture #31 at the top includes "RML-1" which stands for "Rich Murray Lens 1", but I remain somewhat unconvinced that this rather amateurish picture proves anything.

The primary recipient of the e-mail was Malcolm Fairbairn who just posted an interesting paper arguing that if the CSL-1 event is caused by lensing, it is likely to be a cosmic string rather than a dark matter filament because in the latter case, the corresponding tidally disrupted dark matter halo would have to be as heavy as the Milky Way - and such a halo seems to be absent in other data.

This was always our primary worry - that CSL-1 could be caused by lensing by something that just acts as a string but can be of a rather conventional origin.

Movie: Loners (2000)

Ying, a Chinese girl who speaks Czech, invited us to screening of a Czech movie (with English subtitles) in the Department of Visual and Environmental Studies (VES). It was the first time I saw Samotáři (Loners, 2000) and it was pretty good.

Much like in many other Czech movies, the seven central characters seem to have a pretty difficult, dirty life; the web indicates that this theme was popular among the U.S. movies in the early 1990s. Their relationships are breaking up, combining, and recombining. Another typical feature of the post-1989 Czech movies is that neither of the characters is designed to be a universally negative one and neither of them is a permanently positive character either. Also, you can see how the characters judge the features of others depending on the context; that's a very realistic feature of the movie's psychological analysis.

Ondřej is a talented and married young surgeon who has two daughters. Nevertheless, you learn that he has only studied neurobiology to prove how much he loved another woman, Hanka. He is so obsessed that he repeatedly dresses up as a plumber to get into Hanka's parents' house - a house that he repeatedly burns.

Meanwhile, Hanka has a very mixed relationship with her parents. She just decides - by tossing a coin - to break up with Petr who works in a private radio station. Hanka does not view her parents' bourgeois life as a good example but seems rather unsuccessful in creating a better environment. But she is a very flexible figure, as far as the type of her boyfriends go.

For a while, Hanka seems to have serious plans with Jakub, an innocent drug addict whose memory seems to be rather devastated by the drugs. However, the friends from his band inform Jakub that he already has another girlfriend. Hanka is disappointed and returns to her parents.

Friday, November 11, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Discrimination against white males and conservatives

As Sean Carroll has pointed out, the U.S. justice department plans to sue a university, namely Southern Illinois University (SIU), because it discriminates against whites, males, and others - by establishing a wide spectrum of fellowships that are not available to whites and/or males; see the article here. Unlike Sean, I agree with the Justice Department that beyond a certain plausible level, these things simply are illegal and undesirable and it is a task for the Justice Department to act.

Not surprisingly, Barack Obama supports the discrimination, too.

Don't get me wrong: I may have been involved in increasing the fraction of females or other minorities - and maybe even females from the Axis of Evil - in our own department; by the way, some of them being very nice and attractive. ;-) But whenever my decision was twisted by similar considerations, I was very careful to check that the law gave me the right to act in one way or another in a given situation and that the decision was not manifestly counterproductive. If someone establishes several fellowships whose only purpose is to selectively choose people from certain groups that are defined by their race, nationality, or gender, and to exclude the complementary groups, then it seems pretty clear to me that the person has violated the federal laws and probably the U.S. constitution itself.

This is about the validity of very basic U.S. laws and someone's belief in some particular ideologically scientific opinions that all groups have the same average XY where XY is any observable simply can't justify a crime.

When I talk about the laws, I mean e.g. the fourteenth amendment of the U.S. constitution. The Cornell legal interpretation says, among other things:

  • "A violation would occur, for example, if a state prohibited an individual from entering into an employment contract because he or she was a member of a particular race."
No doubt, this clause is violated by the fellowships. Technically, the Justice Department will probably not use the amendment but rather Civil Rights Act of 1964.

Helping to increase the fraction of a certain group in Academia may look as a good plan to some people, but if it contradicts the federal laws that define in what respects the people have to be treated as equal by major institutions, then there is no doubt that the U.S. laws are primary. I think that the constitution and other laws are very balanced, stable, and clear, and a violation of these rules is not right.

Flying cars from string theory

Our colleague Song Yoo-geun, who is eight years old, has finished his elementary and high school in 9 months, instead of 12 years. He just joined a college near Seoul and impressed the professors by his explanation of the Schrödinger equation. His next goal is to work at CERN and develop flying cars based on superstring theory.



Because Song does not like to communicate with ordinary adults too much, his father has explained that Ramond-Ramond or Neveu-Schwarz-Neveu-Schwarz forces are able to compensate gravity as a consequence of supersymmetry, which makes flying BPS cars float in the atmosphere.

Thursday, November 10, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Higgs at 105 GeV?

As Jacques Distler reminds us, we normally argue that LEP has imposed a lower bound on the Higgs boson mass: 115 GeV. Slightly below this level, maybe around 105 GeV, there can be a viable candidate that was seen as a weak signal. However, it contradicts the previous sentence about the lower bound and we usually discard the signal.

Are we doing a wise thing?

Dermíšek and Gunion argue that in next-to-minimal supersymmetric standard model (NMSSM) two things happen: first of all, with the lowest possible fine-tuning you can imagine, the Higgs is predicted at 105 GeV. Second of all, the decay channels are a bit different, the classical decay channel weakens, and therefore 115 GeV is no longer a lower bound on the mass.

In other words, it is plausible that LEP has seen a small signal for the most natural value of the Higgs mass in the second simplest supersymmetric extension of the Standard Model you can imagine. Note that the Standard Model itself was also the second simplest theory with an SU(2) gauge group you can imagine. ;-)

If this NMSSM scenario were right, I would prefer not to share Jacques' bitterness about the difficulties with observing Higgs directly at the LHC. There could be more interesting things to observe! ;-) Looks like I am not the only one who told this thing to Jacques.

Wednesday, November 09, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Modern science-haters

Clifford Johnson describes a talk by one of these modern science-haters whom we discussed several times. It seems that some ideological presentations of the creationists are as honest as the holy word in comparison with this gentleman.

Clifford's report confirms the hypothesis that it is never just string theory that the science-haters dislike and want to humiliate in the context of modern science. This particular science-hater also claims many other things. Modern science is ridiculous and equivalent to the theory of Intelligent Design, he argues, because

  • it uses the concept of infinity. For example, the mathematicians are crackpots, he explains, because they have proved the Hilbert's hotel theorem. (I have not heard the original formulation but trust me that this captures the essence.)

I find such a statement incredible. The Hilbert's hotel theorem, showing that the infinite-dimensional Hilbert space is isomorphic to the same Hilbert space with an extra one-dimensional space added (an infinite hotel can always accomodate an extra guest) is not only a rigorously proved simple theorem, but it is also a theorem relevant for physics (which is not the case of all theorems in mathematics). You don't need to talk about the spectral flows: the very existence of the creation operator acting on the harmonic oscillator is a physical example that the theorem is relevant in physics. Also, this science-hater humiliates the fact that

  • "zeta(-1) = -1/12" and it can be used to obtain modular-invariant regularized results for various divergent sums.

I just personally find it amazing that some professional physicists have problems with various regularization procedures and with the very concept of infinity - roughly 60 years after these concepts became completely essential for doing virtually anything in theoretical physics. (Arguably, the concept of infinity has been crucial in physics for several centuries.) PhD committees should probably insist that anyone who deserves a PhD in theoretical physics should know not only how the symbol of infinity should be manipulated with, but also why the Casimir energy in 1+1D leads to an expression proportional to the sum of integers, and why "-1/12" is the only correct answer one must assign to this sum.

Notes on two papers

Brustein and de Alwis study a thermodynamic description of the early cosmology and argue that the tunnelling tends to end up near extrema of the potential, and close to the "center" of the landscape where the coupling is of order one and the sizes of the internal manifold are close to the self-dual radii, taking KKLT as a moral example. This seems to agree with the observations of physicists such as Alon Faraggi that the self-dual dimensions of order one are preferred. I also believe in this kind of stuff - the vacuum selection mechanism that we will eventually find will favor the most "canonical" vacua which may be those that are close to the center. This idea is somewhat related to the "beauty is attractive" business but its focus is not on enhanced symmetries.

As far as I understand, John Baez:

  • rediscovered that the Standard Model group is SU(3) x SU(2) x U(1) divided by a certain Z_6 group
  • rediscovered that the complex spinor 16 of spin(10) is a good representation for a single generation of quarks and leptons - i.e. rediscovered one reason behind grand unified theories
  • realized that SU(5) is actually a subgroup of SO(10), not only spin(10), that moreover does not include the 2.pi-rotation and therefore the spinor is single-valued
  • rediscovered that manifolds with SU(5) holonomy are called Calabi-Yau five-folds
  • wants to study, for a very incomprehensible reason, manifolds whose holonomy coincides with the Standard Model gauge group

The last point seems rather unnatural to me because the holonomy is exactly the symmetry - a part of the tangential group - that is broken by the manifold’s curvature, while the gauge group of the Standard Model is a group that must be, on the contrary, completely unbroken to start with.

Tuesday, November 08, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Krauss on science and religion

Lawrence Krauss has an essay in Tuesday's New York Times in which he argues that theoretical physics, as long as it's not just a telephone directory summarizing the experiments that have already been done, is more or less on par with religion and Intelligent Design.

What do I think about these comparisons?

See Mark Trodden's text for his viewpoint.

Science and religion have definitely common roots. The ancient people used to be scared by many natural phenomena they did not understand and they started to produce various "theories" how the world works and what you have to do to save your life and protect yourself and your community from various threats. Some of these "theories" were rather complex. This complexity is what distinguished the early believers and the early scientists from average people who only cared about their Tuesday lunch.

The ancient protosciences and protoreligions made the people focus on certain questions that transcended their lives. They helped us to transform ourselves (i.e. monkeys) into humans. They taught us to spend a certain amount of time with activities that were not immediately necessary for our survival. They taught us to make big conjectures. Even Newton has constructed his mechanics in order to support a more far-reaching concept - namely the holy spirit that fills the space. Religion and science have co-existed for millenia.

Once again, scientists and believers have always shared certain characteristics and millions of words have been written about these relationships. Moreover, in the ancient era, it was often difficult to distinguish which activity was science and which activity was religion or unjustifiable superstition. If Lawrence Krauss wrote his "essay" 30,000 years ago or maybe even 500 years ago, it would have been almost correct.

But surprising as it may sound, it is 2005 right now and Lawrence Krauss is no longer right. Religion and sciences have been separated several centuries ago. Science has claimed certain questions to belong under its umbrella and it has pretty well-defined procedures that are used to decide whether a conjecture is correct or at least convincing or not.

Whether or not warped geometry or a Calabi-Yau manifold reminds Dr. Krauss of Moses is completely irrelevant for science. Science works independently of these beliefs and only rationally justifiable arguments have the power to influence where science goes. The apparent mathematical inconsistency of all purely four-dimensional theories of gravity is a powerful scientific argument; Krauss' religious or anti-religious feelings and vague articles in the newspapers are not.

Lawrence Krauss clearly misunderstands and understimates (and maybe even misunderestimates) how serious the UV problems of gravity or the hierarchy problem, among many other examples, are. He may choose not to solve these questions because they may be uninteresting for him. Billions of people in the world do not care about science unless it may directly improve their life today. But these people are not expected to be those who determine the direction of the scientific research.

Krauss is quite clearly unhappy that physics has become counterintuitive after the 20th century revolutions. It is no longer transparent for most peasants. What a sad development! However, most of us are quite satisfied or even excited because exactly this feature measures the depth of the scientific progress: how many deeply counter-intuitive insights can we establish. Be sure that this process will never be reverted. Science simply is more complex than it used to be 600 years ago.

Science and religion share fascination by unseen things. But they differ in their method how to decide whether the unseen things exist or not.

Calabi-Yaus from MSSM

Last week or so, James Gray has given a very interesting talk about their work on deducing the details of string theory from low-energy physics. Normally, the string theorists start at the top. You pick your favorite compactification (you decide whether it is heterotic or type II, what is the shape of extra dimensions, which fluxes and which branes you allow), figure out what its low-energy spectrum is, and deduce the moduli spaces, couplings, and low-energy effective field theory in general.

They propose the reverse approach. Take one of the simplest low-energy phenomenological models compatible with your observations - such as the MSSM. Define its gauge-invariant monomials to parameterize a moduli space; these are used as F-terms or D-terms. Determine the dimensionality and topology of the resulting moduli space. And find a string model that exactly matches it.

They often mention that they would like to derive that the moduli space is a Calabi-Yau three-fold itself. I find it a bit exaggerated. The Calabi-Yau space can only be a moduli space at low energies if you consider something like one D3-brane on Calabi-Yaus in type IIB - but there are really no phenomenologically viable models of this kind. Note that the 3-fold in the F-theory flux constructions is not a Calabi-Yau manifold.

In reality, the moduli spaces at low energies describe the moduli spaces of shapes of manifolds such as the Calabi-Yaus or moduli spaces of gauge bundles over them. They can have many different dimensionalities and topologies. In the top-down approach, we know very well what is a natural requirement for a model to be phenomenologically appealing: we want to get as close to the Standard Model or MSSM as possible, and remove all exotics.

A corresponding task in their bottom-up approach is not quite determined, as far as I can see. What properties should the low-energy moduli spaces derived by their algorithm have in order to tell us that it looks like it comes from string theory? I think that the idea that it should be a Calabi-Yau manifold is naive, and I don't have any better replacement for this proposed answer.

For example, they seem very excited by having obtained a moduli space whose Hodge numbers coincide with those of a CP^2:

  • h0,0=h1,1=h2,2=1

and otherwise zero. I personally have not understood why this "simple" Hodge diamond is more attractive than other Hodge diamonds that they could have derived.

Monday, November 07, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Great October Revolution

For one half of my readers: Congratulations to the 88th anniversary of the Great October Revolution! Well, it was not great, it was not in October, and it was not a revolution but rather a coup, but nevertheless,

Well, no longer in Russia, but a celebration in Ho Chi Minh City in VietNam is fine, too. As kids, we could always watch some fireworks before November 7th. In the first approximation, one must be extremely grateful that this era is gone.

On the other hand, we live in a modern, environmentally friendly society, and therefore all the trash from the past is recycled in one form or another - which is why our expected happiness received negative contributions from the second order perturbation theory, much like in most cases in physics. :-)

Sunday, November 06, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Landscape decay channels

One of the reasons why I think that a megalomanic amount of metastable de Sitter vacua in string theory should not exist is that they have a megalomanic number of ways how they can decay.

See also Resonance tunneling and landscape percolation (2007)
Of course, this particular argument can't eliminate the supersymmetric anti de Sitter vacua of the landscape because they are exactly stable. However, de Sitter vacua - which is what we eventually want to get to match reality - can generically decay to other vacua with smaller vacuum energy. Such a process is described by an instanton whose Minkowski interpretation is nothing else than membrane nucleation. A charged spherical domain wall is spontaneously created in space. The interior of this "bubble" carries a lower energy density (which is why it is allowed by energy conservation) and a different value of one type of the electric or magnetic field (a flux over the internal manifold).

If the action of this instanton is "S", the decay amplitude is suppressed roughly by "exp(-S)" and can become negligible if the action is comparable to hundreds or thousands.

But there are actually many types of domain walls that one can nucleate. Each of the basic "types" of the domain walls is able to change one type of the flux by a single unit. In principle, you may consider tunnelling to a much more distant vacuum elsewhere in the landscape. These more convoluted decay processes are suppressed by even greater actions; but there are many such decay channels. Who wins?

In the simplest models you can imagine - such as Shamit+Nima+Savas' model with many scalar fields with a quartic potential - the parameteric answer is actually a tie. If the instanton that induces the flip of a single scalar field from "+v" to "-v" or the other way around has the action "S", then the instanton that flips "k" fields simultaneously may be interpreted as a superposition of "k" copies of decoupled instantons of this type. Recall that the Hamiltonian for these scalar fields is a simple sum of contributions from the individual scalar fields.

And the action of the composite instantons is therefore "kS". If you take "k" to be comparable to "N", the total number of the scalar fields, there are "2^N" decay channels and each of them is suppressed by something like "exp(-NS)". If the elementary action "S" is of order one, the product may be close to one, too. However, it is natural to imagine that there are semi-isolated sectors in which the elementary action is much higher, e.g. 1000, and the instanton suppression wins. In such cases, we can indeed neglect all decay channels except for the fastest one. But note that both factors, the growing factor and the suppression factor, have the same, roughly exponential dependence on "N".

However, in reality, I assume that the action of the composite instanton is parameterically smaller than "kS". My guess is something like "sqrt(k)S". One needs to nucleate a composite domain wall but the tension of the composite domain wall is likely to be smaller than a simple sum of the contributions; a composite domain wall is a bound state of the "elementary" domain walls. If you take the guess "sqrt(k)S" for the action, justifiable by the Pythagorean theorem in the configuration space (landscape) or the analogy with the (p,q) strings, as your starting point, the total decay rate will go approximately like
  • 2^N exp(-sqrt(N)S) ~ (morally) ~ exp(N-sqrt(N)S)

You see that for really large values of "N", being many thousands, the positive term in the exponential dominates and the decay rate becomes fast. The minimum of the exponent appears at

  • N = S^2 / 4

If you assume that the elementary action "S" is, for example, 60, the resulting "N" that maximizes the lifetime will be around 1000. That's still large because it gives you 2^{1000}=10^{300} vacua, but still, you see an argument that the number of long-lived de Sitter vacua should not be allowed to grow indefinitely. You may either think that this argument is flawed or irrelevant, or you may think that in reality, the numbers are actually much more stringent - and closer to one - and your conclusion will be that the number of stable de Sitter vacua must be reasonable, too.

At any rate, the statement that there are googols of nearly stable de Sitter vacua is a rather strong statement - imagine how weird it would be to argue that there are 10^{500} stable states of the Hydrogen atom - and I would expect a rather extraordinary body of evidence, including a detailed refinement of the ideas above, before their existence is accepted as a consequence of string theory.

Once again, this argument does not affect the anti de Sitter vacua. It may be a bit puzzling to have zillions of anti de Sitter vacua - and their dual conformal field theories -too. But maybe this is how the (supersymmetric) life eventually works.

French Intifada

As you know, France is experiencing the worst days of rioting since the 1968 student protests. I am afraid that the country has allowed more immigration than it can handle. By the "ability to handle", I probably mean a working system and infrastructure that can integrate a vast majority of the immigrants into the society.

Charles de Gaulle used the military in 1968 and it was one of the reasons he had to resign in 1970. Nowadays, the government prefers to issue a "warning" that the rioters could spend many years in the jail. In my opinion, this is no real warning. Instead, such a statement assures them that they can't be shot and they can probably always escape as long as they know how to run or drive a scooter.

One of the things I could not resist to look at was the attitude of the Muslim countries. An agency that shares the name with the most influential agency in the region,

(Suvrat explains below that it is actually a different Aljazeerah than the "regular" Aljazeerah), used the opportunity to summarize all criticisms and dirt they have against France and its perceived discrimination.

Comments by the readers

As an Irish reader notices, the French are not getting much credit for their opposition against the Iraq war. Well, that's hardly surprising. The second commentator is a French muslim who thinks that the riots won't help anyone. The third contributor is from Tunisia and he announces that France will be destroyed for mocking them, among other things, by headscarf bans. The fourth one is an American who conjectures that NATO and the U.S. will be the only one that will be able to save the French who were on wrong side of the history a few years ago. The fifth one, Dr. Khan from Holland, tells the "demonstrators" to keep on fighting against "discrimination". Another American advices the French muslims to work hard or return home and preserve their habits. Mshakir from Somalia surprisingly says a very similar thing. Abdul Mateen from India recommends to follow his prophet. Tuna hunter from Philippine seas explains that the French have always been soft against fascists. And so on, and so on.

In Israel, many people think that Paris "deserves it". Europe is already a battleground in the war on terror. And political correctness in France prevents the police to stop crime. RedState.ORG, a major right-wing blog, argues that blood is necessary on the streets of Paris today to prevent a greater tragedy tomorrow.

A corrected list of authors

Several versions of the anti-Hagedorn paper we discussed here, including some editions submitted to journals, as well as three more papers temporarily had the name of Joe Polchinski on the list of the authors. Euphemistically speaking, it was a typo. Joe Polchinski is not a co-author and does not believe that the paper is (or papers are) based on a rational idea.

The editors of journals and others are encouraged to learn that a combination of these two names (SC and JP) on a future paper will likely be another typo. More details here or here. I ask the commentators to avoid comments that could be inappropriate in this slightly sensitive context.

Jágr's smile and jokes

Let me admit that I find most athletes uninteresting. Jaromír Jágr, the NHL superstar, is definitely one of the major exceptions. Lee Jenkins wrote an article in the

about this Czech athlete who has become a key player of New York Rangers and who is again the leading scorer and the dominant right wing in the league. What's so special about Jágr?

First of all, he likes freedom. Others usually prefer the money and the fame. The communists stole the farm of Jágr's grandfather and arrested him for several years. Jágr's grandfather died in 1968, during the Prague Spring. Jágr has been using the number "68" ever since.

As a schoolkid, not surprisingly, he kept a picture of Ronald Reagan in one of his schoolbooks or wallets. (So did I.) I am sure that most readers are completely unimpressed by these feelings, and they are wrong. Happy 25th anniversary to all Reaganites! It's been quarter a century since Reagan defeated Carter. (Jágr spoke to Reagan in 1992 via telephone and the conversation may have been difficult because he did not know what Gipper meant etc.)

Jágr also enjoyed to be himself as a player whose salary was as high as 11 million USD. Well, such a situation opens new dimensions of freedom, including room for heavy gambling, speeding tickets in fast cars, new arcade games, other symbols of Jágr neverending childhood, and occassional debates with the IRS. Two or three years ago, his difficult years were caused partly by the limitations imposed on his freedom and on his jokes and partly by the breakup with Andrea Verešová, a former Miss Slovakia (2003).

Well, yes, another reason for my understanding of Jágr is that I can imagine very well that it is discouraging if your Slovak girlfriend is not functioning properly. She is an attractive woman; but things look very different from the viewpoint of eternity.

Saturday, November 05, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Hydrinos

A reader has pointed out that The Guardian, a British left-wing daily, is promoting the theory and industry (power plants) based on the "hydrinos" invented by Randell Mills, a Harvard-trained medical doctor, and investigated by a "hardy band of scientists", as the newspaper calls the undereducated or corrupt humans who believe this stuff. Hydrinos are supposed to be small versions of the Hydrogen atom. No muons are involved; indeed, Mills also wants to kill the uncertainty principle. Forget your 143a Quantum Mechanics I as well as billions of experiments that confirm it in detail.

Instead of the muons, the theory underlying Mills' activities is based on the assumption that quantum mechanics should be replaced by the so-called "Grand Unified Theory of classical quantum mechanics"; and that we should also abandon the Big Bang theory. Randell Mills is no small fish among the crackpots. By 2000, he had collected 25 million USD for his "BlackLight Power Inc." company. He has actually built a factory and no doubt, his banking account is much richer today.

How much energy does Mills get, according to his own words? He can get 1000 times more than the conventional fuels, he says. Also, Mills has demonstrated that he is able to multiply "2 times 13.6 electronvolts". He obtained 27.2 electronvolts. He argues that his "catalysts" absorb 27.2 electronvolts from the Hydrogen that is becoming a hydrino.

In 2000, Mills also promised to fill California with hydrino plasma cars. He claimed that he had make breakthroughs in artificial intelligence, cosmology, medicine, and gravitational jujitsu.

Friday, November 04, 2005 ... Français/Deutsch/Español/Česky/Japanese/Related posts from blogosphere

Anthropic Weinberg

Steven Weinberg is an exceptional physicist. He not only gave the name to the Standard Model, but he also discovered it - in the old era when it did not include QCD yet. He has made lots of other discoveries and he is still "in" and he even follows the very technical recent discoveries in string theory. Many of us have read his popular books such as The First Three Minutes and Dreams on a Final Theory and they influenced us tremendously.



One of his controversial but equally successful predictions was the prediction of the rough size of the cosmological constant assuming the galactic principle. If cosmology allows the galaxy formation, the cosmological constant can't be too large because the space would expand and dilute too quickly, before the clumps can be created by the gravitational pull. But it definitely can't be too negative either because the Universe would approach the Big Crunch too early.

There is an allowed window - the anthropic or galactic window - and the measurements in 1998 confirmed that our Universe seems to be somewhere in this window on its preferred, positive side. Although I am sure that Weinberg hates the idea of the anthropic principle deeply in his stomach and mind, he decided to accept it. And because his comment about the cosmological constant is the only at least partially and superficially successful prediction of the anthropic principle among those that can't be explained more accurately, he became a true prophet of the Anthropic Church. In his opening talk

Weinberg presents some novel ideology to support this principle. The biggest revolutions of physics not only answer questions in new ways, but they even change the classification which questions are important and well-defined. And the anthropic principle and the landscape seem to be doing something similar, he argues. Asking for an explanation of the values of the parameters of the Standard Model is equally meaningless as asking how to describe the interior of an electron or how to explain that aether causes no winds, Weinberg suggests.

Most published findings are false

Press ESC if you're getting the annoying window from counter.cz. It should disappear soon.

Via Wolfgang Flamme, a reader of Stephen McIntyre's blog.

In his article,

has analyzed various things like the publication bias (attempts to get a signal even though there is no signal and select the findings that have found one); the reverse bias (less frequent; tendency to hide signals); the probability that a finding is published as a function of the previous probability estimate that the result is correct, and some other factors. Insert these variables into some matrix differential equations and look at the outcome.

The conclusion is quite clear: most published research findings are false. Well, let me mention that the analysis focuses on life sciences but the conclusions could probably apply to many other fields of science, too. Hopefully not all of them. The fields based on statistics and phenomenology are probably affected by the mechanisms mentioned by Ioannidis.

The author shows that the probability that a published finding is false increases (or is greater) if and when

  • the sample size shrinks - obviously, the quality of statistics decreases
  • the size of the "effect" in a given subfield becomes small; not surprisingly, it is harder to measure whether XY increases the risk of UV by 0.1%
  • the fraction of relationships that are tested becomes small (e.g. when the total number of possible relationships becomes large)
  • designs, outcomes, definitions, and analytical modes of the field are flexible
  • financial and other interests and prejudices are high
  • the scientific field is hot (studied by very many teams); this point may be surprising to many

I don't guarantee that Ioannidis' article is quite correct - don't forget that it is published and most published findings are false :-) - but it is definitely an interesting set of ideas and mechanisms that may deserve a further mathematical simulation.

Incidentally, you can look at the list of the factors that increase the probability of false publications and compare them with the "global climate change". It is not hard to see that this research "passes" all of these tests. It studies one number - the average temperature - in a very small number of years. The anthropogenic effect is smaller - in fact much smaller than the natural interannual variations. Among millions of factors that may influence the climate, the "experts" only test a few, especially the relation between the CO2 concentration and the average temperature. They can adjust their GCMs in millions of different ways. They have huge financial and political interest to have a certain kind of outcome. And finally, the field is "hot" and studied by many people; they admit it themselves and they are even proud about it - which is why we often hear the oxymoron "scientific consensus".