Piano Man is not Strnad

Tomas Strnad appeared on Czech TV today.

• Strnad on Czech TV

I personally don't think that he looks like the Piano Man at all. Another theory has been ruled out and the identity of the Piano Man remains a mystery.

Ashoke's heterotic black holes

We returned from a seminar at MIT. Ashoke Sen was checking the entropy of heterotic black holes. At weak coupling, such an object has to look like an excited heterotic string. A heterotic string is made of two types of important excitations:

• the left wing
• the right wing

Note that both wings are important. The left wing gives it its potential instability and tachyons and ugliness. The right wing, on the other hand, gives the heterotic string its supersymmetry, beauty, and stability. ;-)

The number of left-moving and right-moving excitations must match. If you imagine a compactification on a circle - times a 5-torus - you may still obtain supersymmetric states that satisfy

• N_R = 0, N_L = n.w+1

where "n" is the momentum along the special circle and "w" is the winding. Note that the difference between "N_L" and "N_R" is determined by the level-matching conditions, and in the presence of momenta and winding, it is not zero but rather "n.w+1". There are no right-moving excitations, and because supersymmetry is only carried by the right-movers, it is not broken.




At strong coupling, these supersymmetric states become black holes. Ashoke constructs the corresponding black hole solutions of four-dimensional supergravity by a special solution-generating method involving T-dualizing of a Schwarzschild solution, but others - such as Natalia Saulina - could find the solution directly. ;-)

The question is whether one obtains the right entropy. The entropy in the CFT is, according to Cardy's formula, something like "4.pi.sqrt(n.w)" for large values of the momentum and winding. The leading black hole entropy is "A/4G". So do they agree? The classical area of the horizon turns out to be zero. Ashoke Sen then argues that

• the stringy loop corrections are absent in the appropriate limit
• the alpha' corrections are relevant
• the alpha' corrections have the correct scaling with the charges by two scaling arguments
• the coefficient must be checked
• the coefficient is not "log(3)" as in loop quantum gravity but rather "4.pi"
• this number is hard to calculate because the number of higher derivative terms is huge, but surprisingly, if one only considers the F-terms - those that are calculable from topological string theory - one obtains the correct corrections, indicating that no other corrections contribute to the black hole entropy
  

Would-be Goobers and Senators will come together by July...or thereabouts

I've blogged about this before: what happens relative to all the high-profile Texas political tilts in 2006 depends on the proclivities of the Honorable Kay Bailey Hutchison, as Texas Monthly details in an article from the May issue titled "Kay Sera Sera" (behind registration and a password found only in the print edition).

Here's a sample:

... All those ambitious pols down in Texas are twiddling their thumbs while you make up your mind. Not that you owe them anything; most of the statewide officials—except Comptroller Carole Keeton Strayhorn, who may run for governor herself—have already endorsed Rick Perry. It’s a toss-up who’s more craven: Perry for asking them this early or them for doing it. Now you’re holding up their game of musical chairs, especially in the case of David Dewhurst, the lieutenant governor. He wants to succeed Perry in 2010, but if you beat Perry, he’s stuck in his current job for eight more years. So he might opt to run for your Senate seat, leaving his job open and touching off another mad scramble. Congressman Henry Bonilla, of San Antonio, has already said he’ll run for the Senate if you don’t. Strayhorn and Attorney General Greg Abbott would look at the lite gov’s office Dewhurst would be vacating, and railroad commissioner Michael Williams and Texas Supreme Court justice Harriet O’Neill are said to be interested in the AG’s job. Yes, all eyes are on you right now.

And apparently she's going to make a decision shortly, though there's some risk in continuing to shilly-shally:

Your waiting until summer to announce your plans runs the risk that Strayhorn might throw her hat in the ring first. In a three-way race, the likelihood is that you and Perry would end up in a runoff, but then the danger would be that those November Republicans and crossover Democrats might not return for the runoff, while the party faithful will. Advantage Perry.

So there's some interesting bits in there, but there's also some bullshit:

Let’s talk numbers. The Republican primary is the only race that matters. No Democrat can win, and Kinky Friedman isn’t Jesse Ventura.

Even though Paul Burka is by his own admission writing this article in the voice of a Hutchison political consultant, that's wrong on both counts. The only scenario in which the Democrats have no chance is if John Sharp decides to run for anything (this is assuming that Tony Sanchez isn't so stupid as to waste more of his personal fortune; an admittedly tenuous assumption). Kinky Friedman is going to be able to gather something like 15% of the votes in a general election -- give or take 5% -- with most of that peeling away from the Republican candidate (the 'pubs have more votes to lose, after all). While that won't be an impact like Jesse "The Body", it will be Ross Perot-like electoral influence. And Chris Bell is the man who stands to capitalize on GOP fatigue statewide, as evidenced by the following, which Burka wrote right before he wrote that above:

... there are pockets of the state where Perry has angered Republican voters: places like Abilene, which lost its congressman in redistricting; the Dallas suburbs and Austin, where toll roads are unpopular; South Texas, which has not benefited from the largesse Perry has showered on companies to entice them to Texas; and the medical community generally, which didn’t like his health care cuts. You can make inroads into these constituencies, although you’ll have to “me too” the ideological stuff.

His critics see him as a do-nothing governor, but he’s really more of a do-the-wrong-things governor. The first priority of Texas governors has always been education; Perry imposed budget cuts on both public and higher education in 2003, notwithstanding that education was one of his original areas of emphasis (along with the border, which he has likewise given short shrift). Instead, he has thrown his efforts into the aforementioned economic development and toll roads. And yet the long-standing view in Texas, under Republican and Democratic governors alike, is that improving education is the best economic development program there is.

The Abilene congressman mentioned is Charlie Stenholm, who in my humble O would be the Democrats' best candidate for US Senator, considering that Ron Kirk will apparently not be running. But Stenholm evidences no particular interest in returning to Washington; his websites are currently blank and he allegedly turned down President Bush's offer of Agriculture Secretary following his defeat in November. Martin Frost, Max Sandlin, and Jim Turner, all of whom were likewise displaced by the GOP gerrymander, strike me as weaker candidates for statewide office (Frost managed to also look bad losing the contest for DNC chair). Those men would be better served running for down-ballot slots like attorney general or treasurer or railroad commissioner -- strengthening the bench and laying the groundwork for a top-ticket run in the future. The Democrats are in a lot more trouble trying to win back a Senate seat than they are in removing Tom DeLay's bitch from the statehouse, especially if they wind up with a candidate with scant name recognition and no previous experience having been elected to something.

Texas will continue to be a one-party state for only as long as Texas Democrats continue to concede it as such.

Whatever happens, put the popcorn in the microwave and stay tuned, because it's going to be entertaining.

I think we should send Tom DeLay a sympathy card

I'm a little late on this -- having spent the long weekend in a gloriously cool blue state -- but an anonymous comment in the previous post has graciously reminded me that there's bound to be a little good in everyone, even the slimiest, most corrupt politician ever to walk the halls of Congress.

We all are aware that Tom DeLay has been so unmercifully tormented by demons -- those within himself as well as those external to him -- that perhaps it really would be a nice idea to acknowledge the inordinate stress we sometimes place on our Dear Leaders to, you know, do the right thing.

Julia at Sisyphus Shrugged (with a hat tip to Kuff) has it all ready for you to sign and print.

Go.

France: NON wins

According to LeFigaro.COM, the EU constitution failed in France:

• OUI (yes) 43.46% vs. NON (no) 56.54% are the current partial results

My feelings about the result are mostly positive, but still mixed a bit. France, one of the champions of European integration, rejected the proposed constitution. Most of the "NON" votes had a "wrong" reason, although there have been many reasons behind the "NON" votes, but I completely respect all of them, much like the arguments behind the "OUI" votes. It is totally obvious that the EU constitution would further diminish the chances of French farmers and workers. The Eastern European competition is tough already today, and most French citizens have probably figured out that the further integration of the EU, according to the constitution, would also mean a further wave of uniformization of the continent. In other words, the economic standards of France and the new member states would continue to converge. France has been a payer in the EU budget, and this also implies that the results had to be different from Spain, for example.

Many dissent socialists voted against the constitution because it was not social and environmental enough - the text seemed as an example of the Anglo-Saxon influence that is intended to destroy the French welfare state. Well, that's ironic because the same constitution may fail in Britain or elsewhere because of the opposite reason. But yes, I agree that the text of the constitution has a neo-liberal, free market flavor. The text tried to define too many things. Many French voters agreed with me that the economic principles should simply not be written down in the constitution - such things belong to the programs of political parties and should not be defined in a long-lasting text. More generally, the constitution is just too long. If it were 10 times as short, it would be more reasonable.

The unpopular French prime minister Raffarin is gonna be fired tomorrow. The Dutch are likely to vote against the treaty on Wednesday, too. Some unusual politicians, such as Juncker from Luxembourg, will propose that the EU constitution continues without France. Others will propose another referendum in France. Most mainstream people will agree that the constitution has been stopped cold in its tracks.

Is the Piano Man Czech?

This looks like a pretty interesting and bizarre story. A few weeks ago, a mysterious man in a soaking wet suit was found in Britain. He does not communicate with anyone and is extremely shy. After several attempts to initiate an interaction, he drew a nice picture of a piano, and once they allowed him to play, he was playing classical pieces for 4 hours from memory. An accomplished amateur, they say.

• CNN about the Piano Man (includes a photo)

The British could not find out who he was. The best hint they received was a statement of a Polish mime who illegally works in the streets of Rome. This Pole claimed that the Piano Man was his former colleague from Nice - the French musician allegedly called Steven Villa Masson. A week ago, this source and his piece of information apparently turned out to be good enough for CNN and the theory has been announced by CNN as well as tens of other sources as the final answer to the mystery.

Well, one may feel a bit unsatisfied with this kind of an answer. Don't get me wrong - I have absolutely nothing against the Polish street mimes currently working in Italy. :-) But still, the name "Steven Villa Masson" does not seem to be terribly official as far as I can say. Moreover, Masson has been tracked down in Nice. Today, The Independent offered something better.

• The Independent about the Piano Man

They were contacted by Mr. Klaudius Kryšpín [Clow-dee-oos Krish-peen], the drummer from the most famous Czech hard rock band of the 1980s and 1990s, namely Pražský výběr (Prague Selection, [Prash-skee Vee-b'er]). Kryšpín emigrated to Australia in 1988 and returned to Prague after the Communism collapsed. If you want to hear how Pražský výběr sounds, you should be satisfied with this very low quality file - my version of "Pražákům těm je tu hej" (The natives are doing fine, they can't get lost here in Prague).

What did Kryšpín say? He claims that the Piano Man is Mr. Tomáš Strnad [Taw-mash Stir-nut], his colleague from Ropotamo, an anti-communist teenager band from the 1980s that was immitating (equally anti-Communist) Pražský výběr. Strnad was able to play the piano for hours from memory and attempted to become a classical piano player after 1989 which did not work out. Kryšpín, on the other hand, joined the "real" Pražský výběr itself. The Independent argues that a picture of Strnad from 1983, as shown them by Kryšpín, has a striking resemblance to the Piano Man. If this is true, the man on the picture on the CNN page above must be nearly 40 unless some extraordinary redshift or time dilation changes the proper time! Kryšpín also argues that he knows a birthmark that could identify the Piano Man as Tomáš Strnad.

Kryšpín has not seen Strnad for 9 years. He knows that Strnad did not really get along with his family and 3 years ago he was begging. Kryšpín's brother Richard - the guitarist of their band - now works in Columbus, Ohio as a computer analyst. He also confirms that the Piano Man looks like Strnad, and mentions that Strnad used to have mental problems.

Michael Kocab - the well-known singer of Pražský výběr who also became a politician for a couple of years following the 1989 Velvet Revolution - also said that Strnad may be the Piano Man. Kocab also claims that he met Strnad roughly 2 months ago at a gas station at the outskirts or Prague. Strnad seemed very confused and he mentioned that he would go abroad, most likely to the U.S., to build his career. There is a subtlety however: Kocab argues that this moment when he met Strnad was on April 10th - 3 days after Strnad was officially hospitalized in England.

About our gastronomic adventures (so far)

A quick jump on-and-off to talk a bit about what we're going to be consuming while we're in the great Northeast.

Last night we went to Bella's in Rockland and had a 1 1/2"center cut, bone-in, pork chop (sorry, vegan friends; you may start scrolling now) with vinegar-sauteed peppers, new potatoes mashed with rosemary, broccoli and toasted baguets.

Tonight we're proceeding to this establishment for some German food and ale. Tomorrow, a lobster roll from B&G Oyster Co.

For those of you 'Deadwood' fans, this next line falls under "having a digestive crisis and focusing on suppressing its expression": I noticed Tom DeLay couldn't stay out of the news. I'm sure he was just doing his part to contribute to the Republicans' worst week in a long, long, time.

Cheers!

(We'll be going there, too...)

Hagedorn wisdom debunked?

One of the papers that appeared today is by

• Dienes and Lennek.

They claim that the usual wisdom about the Hagedorn phase transition is incorrect. The usual wisdom is that the exponential growth of the density of states implies that at temperatures higher than the Hagedorn temperature, the second quantized spacetime partition sum diverges because the Boltzmann factor is not sufficient to suppress the exponential growth of the number of states. Alternatively, the Hagedorn transition can be seen as the appearance of a tachyon in the channel related by modular transformations.

Dienes and Lennek argue that this widely believed argument is wrong.

• In the UV picture, the divergence is wrong in string theory, they say, because it effectively leads to you to treat string theory as field theory with many fields, which means that the one-loop integrals over "tau" are made over "Im(tau)" being positive and "Re(tau)" smaller than one-half. The correct stringy integral involves the fundamental domain of the modular group "SL(2,Z)", and if this domain is used, the divergence at the (old) Hagedorn point disappears, they claim.
  
• In the IR picture based on the existence of tachyon, they note that the tachyon is actually projected out by the GSO projections, and consequently, it has no physical consequences. The usual Hagedorn phase transition is therefore absent in heterotic string theories and other tachyon-free superstring theories. They affirm that the Hagedorn behavior in type 0 theories, for example, still holds.
  

They also say that these two interpretations are consistent and related by a modular transformation. In another section of their paper, they propose that the Hagedorn transition in these non-tachyonic theories occurs after all, but at higher temperature than anticipated. The relevant temperature is not derived from a tachyon but rather from proto-gravitons and proto-gravitinos, as they call it. The resulting alternative temperature is universal for all string (heterotic and type II) theories, unlike the conventional Hagedorn temperature where the temperatures differ by factors such as "2" or "2-sqrt(2)". Their new universal Hagedorn temperature equals "a = 1/sqrt(2)" times the temperature that gives you the T-selfdual circumference of the thermal circle. You know that the conventional inverse Hagedorn temperature "beta_H" is not exactly the self-dual circumference under T-duality, and their new one is not either.

The authors also say that one of the conventional Hagedorn transitions does occur but it is a 10th order phase transition where "10" is indeed the spacetime dimension "D" (and it would be replaced by "D-1" if the dimension were odd).

I am curious what others think about this paper.

Off to Beantown

Posting will be sporadic to non-existent through the holiday weekend as the lovely Mrs. Diddie and I take some vacation time in Bahstin.

Try to get by without me.

Lenny's book

According to "amazon.com", Lenny Susskind's popular book will be called

• Cosmic landscape: string theory and the illusion of intelligent design

Lenny has already used this title for several talks. I won't comment on the summary of the book, but it is very provocative:

• The beginning of the 21st Century is a watershed in modern science, a time that will forever change our understanding of the universe, Leonard Susskind, the father of string theory, contends. With this theory, he inspired a generation of physicists who believe that this theory would uniquely predict the physical properties of our universe. Now, decades later, Susskind is revising his theory, saying that it no longer suits our understanding of the universe. In this book he raises the possibility that the Laws of Physics as we know them today are determined by the requirement that intelligent life is possible. In other words, our universe exists because we are here to observe it. THE COSMIC LANDSCAPE will be a paradigm shifting answer to Brian Greene’s bestselling The Elegant Universe.

Scientific American & Giddings

In the most recent issue of "Scientific American," Steve Giddings and Bernard Carr explain why and how the LHC is conceivably going to produce a lot of tiny black holes and what it means for our knowledge of physics and for our survival:

• Quantum black holes in SciAm

There are several other interesting feature articles. John Barrow and John Webb talk about

• Inconstant constants in SciAm.

Well, I could not sign every letter, but some people could find it a cute reading. Another article explains why

• Fat is healthy in SciAm

In another feature article, "Scientific American" defends orthodox science against the Danish skeptical heretic once again and it explains that the true believers in science can be certain even if the results of the calculations are uncertain:

• Shaping the future in SciAm

Another article is about

• Spam in SciAm

Unfortunately I don't have the right to tell you what the last feature article is exactly about - because the text is about a certain

• astonishing array of structural, chemical and functional variations in SciAm...

It is also my duty to inform all the readers at Harvard University and other Ivy League colleges that they are not allowed to click at the link above, and if they have already clicked at it, they are requested to forget everything they have seen. This list also includes the colleague who sent me about 15 e-mails through various remailers a month ago because the survival of that person could not be guaranteed after she saw the article. I was very sad but not surprised to learn who was the sender.

K3 - simplest after torus

This text uses Techexplorer to display math formulae. You may download it but I doubt that it is worth the hassle just in order to see a few cheap formulae in this text.

Superstring theory, according to the conventional wisdom, predicts 10 spacetime dimensions. M-theory, its special state, predicts 11. If it describes the real world, 6 or 7 dimensions must be hidden in one way or another. The simplest way to hide them is compactification: the extra 6 or 7 coordinates parameterize a compact shape (a manifold). The simplest compactification is toroidal compactification where you make the coordinates periodic.

• 
  

Such a treatment preserves all supersymmetries of the original spacetime, and it is not realistic at all. What is the second simplest compact manifold onto which string/M-theory may be compactified? It preserves one half of supersymmetries, it has four real dimensions, and it is the third highest peak in the world after Mount Everest and K2 (as Paul Aspinwall explains in his lecture mentioned at the bottom of this text). How does such a K3 look like? You can either wait for Matt Headrick and Toby Wiseman who are finishing a paper describing the numerical simulations of a particular one-dimensional subclass of K3 surfaces, or you can alternatively look at the following picture:

The animation above was created by Greg Egan and promoted by John Baez. It shows you, once again, how the simplest curved compactification of string theory looks like. Well, not quite. Many K3 surfaces may be written as quartic surfaces in the complex projective space CP3 which in homogeneous coordinates means:

These quartic curves are Calabi-Yau spaces for any values of the coefficients "c" (the complex structure moduli) because of the same reason why quintic (5th order) hypersurfaces in CP4 are Calabi-Yaus: the first Chern class vanishes. Because I have not yet installed the higher-dimensional plug-in into my blog, we had to simplify the quartic complex surface a bit. First of all, one of the homogeneous coordinates in CP3 had to be set to zero which means that we really display the intersection of a K3 surface with a hyperplane. The other three coordinates parameterizing a CP2 were reinterpreted as a C2 and another projection from 4 real dimensions to 3 real dimensions was applied in different ways parameterized by "time". The picture above visualizes a particular surface in R3 connected with a particular quartic polynomial (a special choice of the coefficients "c" was made) - a surface of genus 3 which is known as the Klein quartic:

If you're interested about this surface and its symmetries, read

• John Baez's "this week" 215
• Wikipedia
• Mathworld
• A museum

If you're interested in K3 surfaces and the role they play in string theory, start with Paul Aspinwall's lectures

• K3 surfaces and string duality

The next revolution

One of the discussions at Strings 2005 will be the panel discussion called

• The Next Superstring Revolution

and led by Steve Shenker. We have had many discussions about this topic but I still believe that there are many people (and perhaps readers of this blog) who have interesting ideas that many of us have not heard.

A way to formulate the question is

• What is the most underestimated research direction in current theoretical physics?

Note that the revolutions never start from "nothing". Before the first superstring revolution, Green and Schwarz were doing extremely interesting work that was deeply underestimated by the high-energy community. Also, before 1995, there were several directions that were ignored by the string theorists. This includes Paul Townsend, Michael Duff, and others who argued that the 11-dimensional supergravity was relevant for the grand scheme of things.

It may be that today there also exists a research program that will eventually convince the people that it is the right idea that will allow us a new wave of significant progress. The question is:

• What is it?

Note that the second superstring revolution had merged the communities of string theorists and supergravity researchers although they had mostly been thought of as separate entities. Should we expect something similar in the future?




Loop quantum gravity

Can it be loop quantum gravity that will join string theory? I've spent hundreds of hours with this kind of idea and did not make much progress. Of course it does not mean that no one else can make more progress than I did. Nevertheless there are many reasons to think that loop quantum gravity is truly incompatible with the most up-to-date ideas about theoretical physics. At the same moment it is important to say that some particular methods could play some role in string theory. If you remember, Thomas Thiemann proposed his "new string theory" in 2004 - which was defined as the representation theory of the so-called Pohlmeyer charges. The Pohlmeyer charges, in their original form, indeed became important in recent string theory developments. For example, you can see a paper by Andrei Mikhailov that identifies the Pohlmeyer charges as the origin of "integrability" of "AdS_5 x S^5". It's a pretty interesting stuff that could help to solve the planar limit of this background. Even such a great insight would probably not be enough to spark the new revolution, I am afraid.

Berkovits and RR-backgrounds

Another proposal what the underestimated research direction could be are the Ramond-Ramond backgrounds. Some people, such as Davide Gaiotto, believe that there is something new about the Ramond-Ramond backgrounds that could shed new light on some conceptual issues of string theory; a great example is the strongly curved AdS space that should be described by a weakly-coupled gauge theory - a regime where the power of the AdS/CFT correspondence has not been exploited too efficiently.

Because the Berkovits pure spinor formalism is currently the only approach that allows one to study arbitrary Ramond-Ramond backgrounds - at least perturbatively - it is also the Berkovits' approach that could help in this kind of progress. Nathan Berkovits is a very smart and powerful guy and his equations seem to fit together. However, at the same moment, it is important to note that there are many reasons why others - including the leaders of the field whose name I will suppress here - believe that reformulating string theory in this new language is just a technicality that will not alter the qualitative shape of our understanding of string theory.

Exceptional groups

It is not hard for me to imagine that the investigation of the exceptional U-duality groups may initiate the next revolution. Although we need to understand pretty complicated backgrounds - involving Calabi-Yau spaces, G_2 manifolds, or complicated orbifolds - to describe the real world - and we don't really know "What string theory on these backgrounds exactly is" - there are much simpler backgrounds that we do not really understand. M-theory on six-torus has a "E_{6(6)}(Z)" U-duality group, everyone believes. How do you derive this fact? What is the generalized geometric framework that underlies these exceptional groups in string theory and makes their appearance manifest? The exceptional groups may simply "be there" and they should be a starting point. This is what people like Hermann Nicolai with his E_{10} or Peter West with his E_{11} believe, much like Ori Ganor and others who have also been very excited with this direction. Can a wave function on these complicated infinite-dimensional group manifolds and their (so far unknown) supergeneralizations define all of string/M-theory or at least its 32-supercharge subsector? I can imagine very well that it is the case. When such a dream would be realized, people would have to generalize the conditions that these group manifolds satisfy in order to find a similar definition for the most general backgrounds - ones that would also include the real world.

The exceptional symmetries are also relevant for the Mysterious Duality, another insight whose importance may be underestimated. When I mentioned the Mysterious Duality, I should also say that it is plausible that we will discover that the worldsheets are not quite fundamental but they are rather target spaces of some other string theory - and this self-generating capability of string theory may even continue indefinitely, or be a subject to some bootstrap self-consistent conditions. I've tried to combine and recombine these ideas for a long time but the current state of affairs remains unconvincing although it is extremely tantalizing.

Expansion of topological strings or matrix models

Topological string theory is a nice subfield of string theory that has very deep connections to mathematics and some connections to the full string theory. There are many interesting equivalences operating in topological string theory, for example the quantum foam as a dual discrete description of geometry. It is plausible that these ideas may be generalized to the full string theory. Actually, after some thinking, I believe that the IKKT model is the closest thing to the quantum foam that you can find in the full string theory. It is not quite discrete because the full string theory has many more degrees of freedom than topological string theory which implies that some discrete structures are replaced by continuous ones.

Also, there are links between topological string theory and the matrix models. While these simple backgrounds of (generalized) string theory may be thought of as toy models that are appealing because many properties are exactly calculable, it is conceivable that one may "extend" them to describe more realistic backgrounds. I personally find it unlikely.

Phenomenological attempts

It is also conceivable that someone - or a group of people - is very close to identifying the correct background of string theory that describes reality, and it is a matter of weeks, months, or years before convincing evidence that their background is the correct one will emerge. Among the promising backgrounds, I would list:

• the weakly coupled or strongly coupled (Hořava-Witten) heterotic strings with an "E8 x E8" gauge group and an appropriate Calabi-Yau - the most interesting recent example is the Heterotic Standard Model. This is the class of models that gives the most natural explanation of the particle spectrum - namely the fermions being naturally grouped into grand unified families.
  
• asymmetric orbifolds and free fermionic heterotic models - it is related to the previous item but the Calabi-Yau is replaced by fermionic worldsheet degrees of freedom that are roughly equivalent to a Calabi-Yau near a self-dual radius. While many advantages of the geometric Calabi-Yau backgrounds are preserved, a natural explanation of the number of families (three) may be given in the free fermionic models.
  
• intersecting brane worlds - type IIA with orientifold planes and D6-branes and matter that lives at the intersections. The most attractive feature of these models, as far as I can say, is that the Yukawa couplings may be naturally hierarchical because they arise from disk worldsheet instantons where the disk is actually a triangle stretched between the three relevant brane intersections.
  
• M-theory on G_2 holonomy manifolds - many of them may be viewed as the strongly coupled dual of the previous example. Note that the worldsheet instanton from the previous item becomes an M2-brane instanton in M-theory.
  
• type IIB flux vacua, F-theory on Calabi-Yau four-folds. This is the type of vacua that is the most appropriate one for including warped geometries and Randall-Sundrum ideas. Some people also consider(ed) a large degeneracy of these vacua as another advantage but others disagree(d) and it is reasonable to expect that the importance of the anthropic/statistical approach will start to diminish - after nearly 5 years - because the infinite landscape has just been isolated and it makes any statistical predictions impossible.
  

What do I think are some of the most important unanswered questions

Let me list some of them, and your additions will be welcome. Let me start with the conceptual questions, and then continue with the questions that are important for connecting string theory with reality. The most important conceptual question remains "What is string theory?" But let me be a slightly more specific.

• Conformal field theory on the worldsheet describes all expansions of stringy S-matrices that are perturbative in the coupling constant.
• Is there some generalization of the axioms of conformal field theory that allows conformal field as a special, limiting solution, but also offers some other, strongly coupled solutions?
  
• These extra solutions should include M-theory in 11 dimensions.
  
• Is there some way to define M-theory in 11 dimensions - a variation of the BFSS matrix model, for example - that has shares some features with perturbative string theory so that a unified definition is possible?
• Is there a rigorous way to describe string theory in a language that makes spacetime locality more manifest? String field theory is an obvious candidate but it has its own problems.
• Is spacetime supersymmetry an inevitable component of consistent string-theoretical backgrounds? If it is so, is it always broken below the Planck scale?
• Can we identify a non-perturbative inconsistency of various "suspicious" backgrounds including supercritical and subcritical string theory and/or the large ensembles of flux vacua?
  
• Can we isolate predictions of string theory that are not reproducible in field theory? By these predictions we mean things that are possible in field theory but impossible in string theory - for example, a pure N=2 supergravity in d=4 which is Cumrun's favorite example. Can we prove that such low-energy physics can never arise from string theory?
• Can we describe how does the information escape from a black hole once we believe it is not lost? Concerning the black holes, what happens if an observer falls to the black hole? Does GR describe her life correctly? Are there exact observables associated with this doomed observer?
  

I find it likely that these conceptual questions will have to be answered before we will have the ability to answer the questions that are more closely related to observations. The latter include:

• Can we make general predictions of string theory about the real world that do not depend on the choice of the background?
• Is there a scientific solution of the cosmological constant problem? By the adjective "scientific", I mean a solution that does not require the ideas from the Intelligent Design - or, equivalently, a terribly lucky design - theory.
• Does string theory predict spacetime supersymmetry and if it is so, what is the scale of SUSY breaking? What is the mechanism of its breaking?
• What is the typical size of the additional dimensions? Is it near the naive Planck scale, as the people have been thinking for decades (and reasonably, I think), or is one of the large or warped extra-dimensional scenarios realized?
  
• What is the correct vacuum of string theory that describes the real world?
• Is it possible to calculate the top quark mass, other masses, and other Standard Model couplings from string theory, and predict physics at higher energies?
  
• Does string theory tell us something about the initial conditions of the Universe - something along the Hartle-Hawking lines? Beyond the supersymmetric subsector, this may require the "local" formulation of string theory mentioned above.
  
• Does string theory predict additional objects - or corrections to cosmological perturbations - that are testable? How many types of cosmic strings do we have?
  

No nukes (for now)

And Bill Frist is toast.

GOP moderates in the Senate -- an admittedly endangered species -- yesterday emasculated their majority leader and refused to go along with the "nuclear option", which would have revised centuries-old rules of order to prevent "tyranny of the majority".

God, speaking through Dr. James Dobson, is allegedly unhappy:

"This Senate agreement represents a complete bailout and betrayal by a cabal of Republicans and a great victory for united Democrats..."

More of that can be found here.

Frist looked stricken to say the least. He stressed that he was not a party to the agreement and that he hoped it would end a "miserable chapter in the history of the Senate," but he also stated what he keeps calling the "constitutional option" was still on the table. He also said he "will monitor this agreement closely."

Harry Reid, in contrast, seemed pleased. He said he was willing to work with Bush on his agenda, "but he should have a little more humility."

For the record, the nominations of Janice Rogers Brown, William Pryor and Priscilla Owen will proceed to a floor vote. The rest get no guarantees. The fact that the Republicans needed only 50 votes (with Dick Cheney breaking the tie) in a caucus of 55 means they had six Senators --or more -- who passed on pushing the "nuk-ya-ler" button.

Frist's presidential aspirations (that's the only reason he was doing this, for 2006 and the evangelical bloc) exploded on the launchpad. And John McCain's got stronger. But that's kaffe klatsch for another day.

What the GOP really failed to get was carte blanche on the next Supreme Court nominee.

That wonderful smell isn't just your morning coffee; it's victory.

Savor it, and stay girded for the next battle.

SLAC deciphers Archimedes

The physicist Uwe Bergmann is gonna use the gadgets at the Stanford Linear Accelerator Center (SLAC) to decipher Archimedes' notes - created in the 2nd century B.C. and copied in the 10th century A.D. - revealing how he used mechanical devices to derive various mathematical theorems.

• CNN
• Newsday

A monk in the 12th century vandalized Archimedes' notes and used them as a prayer book. Today, the X-rays should make the iron glow and make the text readable.

Lunch with the Space City chapter of Western Blogonia

(West is left facing north).

I'm the sort of person that isn't content being an online slacktivist. I like to meet the people I converse with online if possible. And I've met discussion forum participants locally and in Austin and San Francisco, and hopefully next weekend in Boston (and recently one site had a Europe gathering I'm sorry I missed) but as I move away from open-season semi-moderated boards to the Wild West of Blogistan I find I get to make a whole new set of friends and alliances.

So yesterday a bunch of us locally got together for some Tex-Mex and political chat.

Specifically the group included this fellow, this lady, this guy, this gal, and "Red Dog", who shows up in the comments of those often but if he has a blog I can't find it. (BK, help me out if I'm blind, pal...)

My first observation is that among the group there might be only one other native Texan besides me, judging from one self-disclosure and the accents. They're also all a pay grade or three above me in terms of formal education, with at least one Ivy Leaguer and several graduate degrees in the bunch.

And I mention the Lone Star connection only because all of these people do a much better job following the Texas Legislature's shenanigans as well as the local political scene -- right down to city hall -- that I can, or intend, to do. Oh, I blog a lot about Deep-In-The-Hearta, as my half-dozen regular readers already know, but it's mostly from a macro perspective (though those freaks in Pearland will undoubtedly continue to draw attention to themselves). And my state representative has lately exposed a particular strain of stupidity, but I'll avoid for now saying something really bad (or good, for that matter) about him. Mostly because it's just too 'inside baseball' even for me.

I'd rather talk smack about John Bolton and Jeff Gannon -- what, you didn't know they were an item? -- than Bill White or Michael Berry.

I hope more of the rest of the H-Town Blogosphere takes Charles Kuffner up on his invite to make these little get-togethers a monthly regular on their calendars. Pete, rastro, this means y'all ...

Infinite landscape

One of the questions that I was always asking Michael Douglas and others who want to treat the "landscape" anthropically and statistically was whether we know that the number of vacua is finite. This includes our discussions with Michael on sci.physics.strings. My feeling always was that the advocates of the anthropic reasoning always wanted us to assume that the number was finite; I was always convinced it was discretely infinite (countable).

The question about finiteness of the "landscape" is an important question because if someone claims that the probabitility distribution on the space of vacua may be approximated by the uniform distribution in the zeroth approximation (and the exact distribution is simply this number multiplied by another, less important function, or it is even exact?) - an assumption that I've always considered irrational - then an infinite number of vacua presents a big hurdle because there is no uniform distribution on infinite sets.

Why do I think that the assumption is irrational? The numbers like 10^{500} are effectively infinite and a rational argument simply should not break down if this huge number is replaced by the true infinity. If there exists any rule that decides about the probability of different vacua, it must undoubtedly be able to imply that a subclass of 10^{500} vacua - or an infinite subclass for that matter - has a vanishing probabilistic weight. Assuming that this is not possible is equivalent to repeating Zenon's error with Achilles and the turtle: Zenon also believed that Achilles could never catch up with the turtle essentially because the path separating Achilles and the turtle may be divided to infinitely many line intervals.

My personal prejudice is just the opposite one: I believe that the classes of similar vacua with too many elements - i.e. the less predictive ones - will be disfavored when we understand things better at the end. It is roughly because the vacua may be organized as a countable set and the populated classes will only appear at the end (close to the infinity) with a very high "ranking" or "meta-energy" and a small "meta-Maxwell-Boltzmann" statistical weight. This will reflect the desire of the theory to be as predictive as possible. But unlike the statistical counters, I admit that this is a pure prejudice, not a piece of science.

So is the number of vacua finite or infinite? Frankly speaking, the number of vacua has always been infinite. For example, the "AdS4 x S7" supersymmetric backgrounds come as an infinite class parameterized by the integer flux. The only way how we may eliminate some of them is to say that the seven-sphere is really far too large and we only want the backgrounds in which the size of the internal manifold is much smaller than the AdS curvature.




A similar situation occurs in the new class of DeWolfe, Giryavets, Kachru, and Taylor. They construct an infinite class of type IIA supersymmetric flux vacua in which the internal manifold may be arbitrarily large. Obviously, if we want to use the statistical reasoning that starts with the uniform probability measure, we must cut most of the vacua off - which means to ban all the vacua in which the compact manifold is "larger" than a certain bound, according to a certain criterion. However, on page 35 they admit the following:

• On the other hand, one can legitimately worry that the conclusions of any statistical argument will be dominated by the precise choice of the cut-off criterion since the regulated distribution is dominated by vacua with volumes close to the cut-off.

Do I think that this example should stop the growth of the anthropic and statistical treatment of the vacua? Yes, much like another blogger, I do think so. It is OK if a few people are thinking in this direction, but it is inappropriate if this approach became the most active subfield of string theory. Any conceivable prediction of the statistical framework depends on the exact statistical distribution - something we don't know yet (and we don't even know whether it is a good question to be asked). The uniform distribution is as far from the true one as any other random guess we may make. The uniform distribution is just a reflection of a prejudice which is as good as any other prejudice (for example, the assumption that the Hodge numbers of the internal manifolds must be as small as possible) - except that this particular prejudice (uniform distribution) cannot work at all because the number of vacua is infinite.

Once again, the goal of theoretical physics is to find the correct theories and correct models, not a randomly chosen probabilistic measure on the space of incorrect models. The latter is unphysical. The theories and models are physically attractive if they reproduce some features of the real world, and if they are mathematically elegant and robust. Concerning the flux vacua, I doubt both features. Nevertheless, it is clear that the "statistical" approach will continue. The authors summarized the main philosophical idea on page 32 of their paper - a refreshing and entertaining quote is included. The first sentence of section 6 also explains the relation of the anthropic principle to religion and it says:

• "To understand God's thoughts we must study statistics, for these are the measures of His purpose" - Florence Nightingale (a famous nurse, 1820-1910)

Stabilization

We at Harvard were looking forward to see this paper for another reason: it looked - and looks - like a truly concrete example of the families of completely stabilized vacua that we are supposed to think about. A calculable construction could allow one to identify the dual conformal field theory and sharpen many conceptual and technical questions. We thought that unfortunately, it was not the case. Their models only stabilize the geometric moduli and there remain other moduli that are not fixed. They are the periods of the three-form but we may call them axions.

But Wati Taylor has pointed out to me that my discussion was too negative: they show that one combination of the axions is stabilized, and they do present an example where this one axion (or combination) is the only axion. In this example, which is also an infinite family, all moduli are stabilized classically, as desired. Thanks, Wati, and also Shamit and Oliver, for your feedback!

Concerning the other classes of vacua with unstabilized extra axions: the separation of the moduli to geometric and non-geometric would be artificial. We have known for more than a decade that they can be related by various dualities and it is important for string theory that these two types are able to transmute into each other. Drawing thick lines between geometric and non-geometric moduli would mean to return physics 15 years to the past. But it is not just a philosophical question: the dual conformal field theory, whatever it is, simply cannot distinguish between these two types of moduli. If the theory is stabilized, it must be all of the moduli that are stabilized. Examples where some moduli are stabilized - and even examples where probably all of them are stabilized but some of them at uncalculable values - have been known for decades, too - and a heterotic example with the racetrack mechanism is mentioned as the first fast comment under this article.

When we now see this model to stabilize all the moduli, one may try to find the dual CFT. Sergei Gukov says that he has some ideas how to find it, for example.

Recent seminars

Three-sentence summaries.

On Wednesday, we reminded ourselves of the whole story of N=2 gauge theory with the SU(2) gauge symmetry - i.e. Seiberg-Witten I - under the leadership of Kirill Saraikin. This nice application of the holomorphy of the prepotential; the known conditions on the allowed behavior around singularities; a known expansion around infinity may be used to reconstruct the low-energy physics exactly. We discussed how much it is known for sure that there are three singularities on the moduli space - of course, the Dijkgraaf-Vafa constructions give us the whole result, including the fact that there are three singularities.

On Thursday, Christopher Beasley who is gonna be at Harvard explained his interesting work with Edward Witten about the non-Abelian localization of Chern-Simons theory. The partition sum was evaluated for a very special subclass of three-dimensional manifolds, the so-called Seifert manifolds, which may be visualized as a U(1) bundle over the genus g Riemann surfaces. Why is it non-Abelian? For their conjecture to work, one must find a group H that acts on the configuration space, and in their case, it is a non-Abelian group.

On Friday, Tasneem Zehra Husain was talking about the SUGRA solutions for M5-branes wrapped on the cycles of various manifolds. She spent some time with introduction - supergravity equations of motion, the conditions for preserved supersymmetry - and the main task is to find out some generally satisfied conditions that hold for the manifolds even after you take the back-reaction into account. The main condition of this sort says that the Hodge dual of the calibration form is closed - i.e. the calibration form is co-closed.

Something's just wrong with this headline:

"Bush promises probe into Saddam underwear pictures".

And yes, there's a photograph. Not of the probe (thankfully).

More all-important rotisserie baseball wryness

From Fanball.com:

News

Remember Jason "Raspberry" Bere? The veteran right-hander, who was coming back from an elbow injury this spring with the Indians' Triple-A affiliate at Buffalo, announced his retirement on Thursday. The injury-plagued former All-Star fashioned a 71-65 record in 203 Major League starts for the White Sox, Reds, Brewers, Cubs, and Indians.

Views

If for some reason you had Bere stashed on a keeper league bench, you can go ahead and release him now and look for a cheap replacement—the kind you find in a second-hand store.

We're gonna "Cowboy Up" with data

Last night the Houston Democratic Forum hosted Dr. Richard Murray, who discussed (along with his son Keir, who also blogs) the creation of the Texas Research Foundation, a progressive think tank to "assist in gathering and disseminating academically sound data on important state issues, and making these findings widely known to business, civic, and community leaders as well as the general public."

In other words, get our message out.

Dr. Murray's expertise is polling, and the state of Texas is woefully underrepresented relative to the quantity (and quality) of polling data of its electorate. Typically the conglomerated media will commission a poll close to the election in order to fill 45 seconds on their 10 pm newscasts and create a week's worth of buzz, and of course the parties fund their own (read biased) pollsters, but again only sporadically and the results are issued mostly when it's favorable to their candidates. So one of Murray's goals for the foundation is to conduct a quarterly statewide poll on issues as well as politicians, one that is academically sound and uses transparent methodology. And as it relates to good news or bad news for Democratic candidates, let the chips fall wherever.

Marguerite has posted here in greater detail (she must've had a recorder, bless her heart).

This is all still in the formative stages, so if you would care to assist in building something like this from the foundation up (no pun) -- and I'm not just talking about donating money but helping to conduct research and "disseminate data", fellow bloggers -- then visit the Foundation's (also still rudimentary) website above.

Hubert Vo and Carole Strayhorn

Local blogmeisters Kuff and Evan have scored with Texas Monthly passkeys (which won't last more than a few days) on two of the more fascinating political stories currently playing out in Deep-In-The-Hearta.

The election of Hubert Vo, the Vietnamese-American and Democrat who toppled Talmadge Heflin in the ferociously contested statehouse race last year, portends a favorable trend:

The fortunes of the Democratic Party seemed bright on a warm evening this spring, when four hundred Vo supporters gathered at a Vietnamese restaurant downtown for a belated appreciation dinner. Chinese American city council candidate Mark Lee worked the room, as did Jay Aiyer, an Indian American city-council-at-large candidate. Against a red-white-and-blue backdrop, students from Alief high schools performed folk dances; girls in sparkling headdresses sashayed to Bollywood songs, and teenagers in white peasant skirts stomped to mariachi music. Vo’s campaign staff was as multicultural as the crowd: His Latino direct-mail consultant was there, as were his African American treasurer, his Pakistani American media consultant, and his folksy Anglo attorney (“We’d like to thank all y’all,” Larry Veselka said to the crowd with a tip of his white Stetson). Vo rose toward the end of the evening to sound the themes of his campaign and thank the audience. His 81-year-old father, who sat a few feet away, beamed. “I will not let you down,” Vo told the crowd to sustained applause. One of the last speakers of the night was Gordon Quan, the city councilman who is considering challenging DeLay. “Hubert provides hope that we can take back this state,” Quan said with a broad grin. “Look around this room. This is Texas.”

... and Carole Keeton Strayhorn, the GOP state controller who has pissed off Rick Perry and David Dewhurst and Tom Craddick with her tight-fisted management of the state's budget (that's a good thing) will likely run for higher office:

“Hogwash on Perry having the base locked up,” she said, interrupting my speculations. “They’re believing their own news releases. I do not mind rough-and-tumble. Texans are ashamed of what is going on now in their state.”

But hasn’t she been reduced to seeking contributions from trial lawyers?

“Hogwash on trial lawyers,” she said.

“When are you going to announce?” I asked, trying not to sound too eager for the answer.

She stared at me. “We view ourselves on the eve of battle,” she said. “We are nerved for the contest and must conquer or perish.” I should have recognized it, but I didn’t. Sam Houston, before San Jacinto.

If you want the skinny on the latest in Texas politics on both sides of the aisle (and keep in mind that what happens here is transferred nationwide shortly after) then go pay those two links at the top a visit and read the entire articles.

Begun, the filibuster wars have

There's a lot of Star Wars jabbering out there so I'd better throw in my dos centavos before the buzzmoment fades.

I put one of my favorite quotes up there in the header. I also like "Only a Sith Lord deals in absolutes," which is OBK's retort to Anakin/Vader, who gets the Bushesque "If you're not with me, you're my enemy." Of course it might be more appropriate to say "Only the Sith (plural is vital) impose false balance on absolutes". Fair and balanced, someone said.

But the only Darth Vader-IS-The-New-World-Order analogy I'm really comfortable with is that Emperor Palpatine is supposed to be Dick Cheney. On second thought, maybe he's Karl Rove. I have trouble telling those method actors apart sometimes.

One thing's for sure: by this time next week, George Lucas will have deposed Michael Moore as the conservatives' pop culture whipping boy. The Voice of the Left (to be despised).

Which begs the question; whatever happened to Ward Churchill?

This is what I get for paying attention to what's going on with our democracy, I suppose

The Houston Independent Media Center liveblogged multiple arrests and police violence at the Halliburton shareholders' meeting in downtown Houston this morning.

Here are photos.

Here's video (RealPlayer).

I couldn't stand listening to the GOP Senators guillotine the filibuster any longer, so I switched over to the local newscast (ABC-13 "Eyewitless News") to see what they might report.

Their last three stories were -- no kidding -- hurricane season preparation, the new "Star Wars" movie opening, and a family of ducklings washed down a storm drain.

I can't get back to work fast enough.

Going nuclear

I am spending too much time away from work today to do my part to save our democracy.

While on the conference call with Harry Reid just now, I had C-Span on mute as John Cornyn spoke. I managed to catch the last of his comments as we completed. Now KBH is speaking about Saint Priscilla. I think she's about to cry.

I've been appalled at the hubris, the arrogance, the unmitigated gall of this administration so many times I'm sick of acknowledging it to myself. It makes me physically ill.

And at this moment I'm disgusted at what an embarrassment -- an abomination -- my two Senators are.

It is revolting that these two people dare to represent all Texans in this debate.

I'll go ahead and give MP George Galloway

this week's Moneyshot Quote:

“I told the world that Iraq, contrary to your claims, did not have weapons of mass destruction. I told the world, contrary to your claims, that Iraq had no connection to al-Qaeda. I told the world, contrary to your claims, that Iraq had no connection to the atrocity on 9/11 2001. I told the world, contrary to your claims, that the Iraqi people would resist a British and American invasion of their country and that the fall of Baghdad would not be the beginning of the end, but merely the end of the beginning.

"Senator, in everything I said about Iraq, I turned out to be right and you turned out to be wrong and 100,000 people paid with their lives; 1600 of them American soldiers sent to their deaths on a pack of lies; 15,000 of them wounded, many of them disabled forever on a pack of lies."

Nuclear option showdown is today

Call Hutchison:

202-224-5922

or one of the District Offices closest to you:

Abilene: 325-676-2839
Austin: 512-916-5834
Dallas: 214-361-3500
Harlingen: 956-425-2253
Houston: 713-653-3456
San Antonio: 210-340-2885

Call Cornyn:

202-224-2934

District Offices
Austin: 512-469-6034
Dallas: 972-239-1310
Harlingen: 956-423-0162
Houston: 713-572-3337
Lubbock: 806-472-7533
San Antonio: 210-224-7485
Tyler: 903-593-0902

Is this the end for Baggy?

Hopefully not.

Tom over at Houston's Clear Thinkers has the definitive take on Bagwell's HOF chances (this is your 'inside baseball' data warning):

In short, Bags should be elected to the Hall of Fame on the first ballot, and it is not even a close call. For his career, Bagwell has an incredible 680 RCAA in 2,135 games (meaning that he has created 680 more runs than an average National League hitter would have created in those games), a .297 batting average, a gaudy .408 on-base percentage (to put that in perspective, an average National League hitter had about a .340 OBP last season), a slugging percentage of .541, and a monstrous .949 career OPS (on-base percentage + slugging percentage) compared to the league average OPS during Bagwell's career of .763 ...

... Just to underscore the foregoing, Mr. (Bill) James -- who knows more about baseball in his pinky than most of us can comprehend -- rates Bags as the fourth best first baseman of all-time in his New Bill James Historical Abstract, behind only Lou Gehrig, Jimmie Foxx, and Mark McGwire.

Get well and get back next year, Baggy.

Gary Shiu's models

Gary Shiu gave the last talk at Columbia, and it was about

• the search for realistic vacua in the landscape.

He showed a picture what such a search looks like: a five-year-old boy is searching for something - apparently a needle - in the haystack. In fact, the boy was Burt Ovrut. The picture offers a striking support for the statement that the anthropic landscape is really the anthropic haystack: Nima Arkani-Hamed confirmed this conjecture by pointing out that the landscape looks like a two-dimensional object.

Gary reviewed basics of superstring model building - stabilization of moduli, SUSY breaking that is apparently able to stabilize all the moduli by itself, the black box treatment of SUSY breaking via soft SUSY breaking terms, and the difficulties to obtain the Standard Model in flux compatifications.

Nevertheless his aim was to describe an example: an MSSM from the flux vacuum at the orbifold



His picture how a compactification looks like was an octopus with many throats - such as the MSSM throat, the inflation throat (that also gives us cosmic strings), and so on. Although this separation of different problems may be appealing for many purposes, I generally find such a picture repelling because progress in theoretical physics should reveal new relations between previously unrelated notions instead of simply approving that they are unrelated.

A difficult problem is to obtain a chiral gauge theory. In the context of flux vacua, this goal is achieved by one of two methods:

• D-branes on orbifold singularities
• magnetized D-branes: this catchy phrase describes D-branes with a non-trivial gauge bundle

The type IIB magnetized D-branes are T-dual to intersecting D-branes in type IIA. The type IIA picture is however difficult to deal with because it involves non-Kähler geometry, which is why these people stay in the type IIB context. In the magnetized D-brane framework, the number of chiral generations is essentially counted by the flux. The Pati-Salam models are natural in this context. The dilaton tadpole may be computed as the number of D3-branes but we really want D9-anti-D9 with a bundle that carries the same charges. One must be careful about the Z2-valued K-theoretical charges. They must be cancelled otherwise Witten's anomaly would appear on lower-dimensional D-branes, Gary argued.

How do the fluxes affect the open string moduli? The self-dual fluxes cancel the forces against gravity, via the usual BPS cancellations, while the anti-self-dual ones double it and they stabilize the positions of D-branes. However, the Wilson lines remain flat directions.

I have a whole bunch to blog about

and a short time to do it. (Hey, just look at the time stamp...)

There were thousands of people at the Art Car Parade and Festival on Saturday. And while the autos were fun, it's always the sideline observation I enjoy best. Some of my fellow parade-watchers didn't look as if they venture outside often during daylight hours, and then mostly just to add another tattoo or watch the band rehearse. Oh yeah, Kinky Freidman's car broke down halfway through, and before he was rescued from walking by a golf cart he blamed the malfunction on a Republican conspiracy.

There were hundreds of people at the "Save America Without DeLay" Family Fun Festival, and while Barbara Radnofsky and Chris Bell and Richard Morrison all had something to say, the most interesting thing was Gordon Quan busting a Tom DeLay pinata (figuratively speaking only; the kids hogged all the real ones). My good friend Lyn specifically asked him to run in the 7th, and he demurred. This leads me to speculate that what Quan really wants is to take on La Cucaracha Grande -- which by extension means Nick Lampson in the Democratic primary. (Aside to Mr. Lampson: why weren't you present at this event?)

And now for something completely different ...

D Magazine asks: who is Joseph T. Farkasdi?

Who is this man? Is he your local Toyota car salesman who wonders, "What do I have to do to earn your business today"? Or is he a conservative blogger, offering "real deep social responsive thought on the most divisive issues of today"? Or is he your ticket to financial freedom, helping you "eliminate all your debts and create new forms of income in less time than you might imagine"? Or is he Joseph with the Sensual Touch, a model, escort, masseur, nude, or semi-nude who offers "special rates for couples, seniors, and groups"?

The answer? He's all those things and more, including motivational speaker and adult filmmaker. Joseph is a real renaissance man. WARNING: search around his sites at your own peril, Joseph likes to be naked--and his enjoyment is a bit too obvious, if you know what I mean.

My observations:

-- anyone with the word "Fark" in their name simply begs ridicule right from the jump; and ...

-- from his candid glamour shots, it appears that Joseph (like his idol Jeff Gannon) is eager to supply his oh, maybe seven column inches -- edited -- of 'top' reporting to anyone who'll take him up on it.

My questions:

-- what Metroplex megachurch does he attend? I'll have a few followups to this question, probably ...

-- how much has he donated to GOP candidates? Yes, yes; data readily available online but I don't have time to look it up, would you mind?

I also saw "The End of Suburbia" over the weekend. 'Troubling' is the best I can do for now. It's a slant on the Peak Oil discussion and how it's affecting us already (with Middle Eastern wars being a byproduct and not the focus). This Houstonian, a member of Cheney's energy task force (you know, the one which we'll never learn what was discussed) was quoted prominently in the documentary. As well as author James Kunstler, who turned up on Salon on Saturday, so that's your primer.

Last night I got in a couple of hours of precinct captain training and then went to the movies again. Again, very upsetting. I'll try to have something serious and coherent to say about them later, but I'm not promising anything.

And just so I don't have to finish this post depressed, here's a letter that Jesus' General wrote to Tom DeLay suggesting a bake sale as fundraiser. Don't forget to click on the 'reports' at the end.

Update: One of our town's conservative bloggers got a little snarky when he couldn't find any posts about the "Without DeLay" Festival, and when I pointed mine out to him, he got even more tetchy. Pretty funny.

Here's another post, Chris. It's got pretty pictures ...

And here's some more photos, and here's some of Kym's pics from the Art Car Parade.

Matrix Big Bang

In the original article, I have described two talks from the conference at Columbia University. Savdeep Sethi chose a topic - his project with Ben Craps and Erik Verlinde - that was the most appropriate one for a conference about string cosmology. And it was a lot of fun:

• The Matrix Big Bang

And because he allowed me to write about it, let's go ahead. It is likely that this article will include some mathematics. If you don't see it, download Techexplorer.

His plan was the following:

• Background - for his talk
• A background - a very simple background where strings can propagate
• Review of BFSS matrix theory
• Its holographic description

Sav explained that string theory has been extremely successful in dealing with a certain type of singularities - the timelike singularities such as orbifold and conifold singularities. Some of them even preserve supersymmetry - but most of them respect the finiteness of the effective Newton's gravitational constant.

On the other hand, string theory has so far been unsuccessful to resolve other singularities such as the spacelike singularities near the Big bang and in the middle of the black hole. Sav's description of the source of the problem is that the scattering quanta always "see" an infinite value of Newton's constant at some moment.

There has been a rather long discussion with Dan Kabat and others why there was really any difference in this respect between the spacelike and the timelike singularities, but Dan eventually kind of agreed. Whatever you do, perturbative string theory is guaranteed to fail near the spacelike singularity and a better description is needed.

Of course, Sav's proposed better description is BFSS matrix theory.

But before he got there, he discussed various singular spaces. One of the simplest singular spaces is the Misner space,



where we used the light-like coordinates and identified them via a boost. This orbifold behaves differently in the timelike and spacelike regions of the two-dimensional spacetime: in the timelike region it defines the Milne universe, while the spacelike part of the space is the Rindler space. (Note that the previous sentence contains inline math, and if it displays incorrectly in your browser, let me know.) This Misner space is locally flat, however. What is the simplest background in string theory after the trivial flat space? Well, it is the almost trivial flat space - which means flat space with a slightly non-trivial dilaton.

To make things really simple, we can take the dilaton gradient to be null.



where the parameter Q is fictitious because a boost changes its value. Note that this simple dilaton background does not spoil the equations of motion for the dilaton. It does not change the central charge either. The central charge of your two-dimensional conformal field theory is obtained from the correlator (OPE) of two copies of the stress energy tensor:



where the dots represent less singular terms. The only effect of the linear dilaton on the stress energy tensor is an extra term



where the second term measures the dilaton gradient. It also contributes to the central charge in the OPE



But if the vector V is null, you see that the contribution vanishes because its square is zero. Also, the spectrum of this theory is isomorphic to the spectrum of the trivial theory with constant dilaton. There is an extra term in the Virasoro generator



which can be combined with another term if we replace



Once again, the spectrum of a single string is not really affected by the linear null dilaton.

That's a fine and simple background. But let us study it in the superstringy context, namely type IIA string theory. In that case, we have enough supersymmetry for the metric to be exact and not corrected by quantum corrections. Also, it may be lifted to M-theory. One obtains a non-flat eleven-dimensional geometry in which ten coordinates shrink as we approach the Big Bang while the eleventh coordinate expands. We first rewrite the metric in Einstein frame where it's not flat anymore:



and then we convert it to an eleven-dimensional metric:



This is a cosmologically non-trivial background with a null singularity. Can we understand it? Can we evolve a state at finite time arbitrarily close to the singularity?

How could we ever do it without knowing what M-theory is? We know one definition of M-theory, namely the BFSS matrix model (Banks, Fischler, Shenker, Susskind). Sav reproduced Seiberg's argument why is the matrix model correct.

You want to describe M-theory in 11 dimensions. You artificially compactify the light-like coordinate



As long as R is taken large, physics is reproduced just fine. This null compactification is on the edge of creating deadly time-like curves, and we should rather define it as the limit of nearly null compactifications which are otherwise slightly spacelike. Any such nearly null (but spacelike) compactification can be boosted, using the Lorentz symmetry of M-theory, to a pure and manifestly spacelike compactification of M-theory. Because the identification was almost null, the new spacelike circle will be very short after the boost and we obtain type IIA string theory with coupling that goes to zero. One can prove that the limiting procedure and the energy regime we want to study (finite energies in 11D Planck units in the original picture) decouples all degrees of freedom from the theory except for massless open string states stretched between N D0-branes - well, N D0-branes is what the boost produces out of N units of momenta in the light-like circle "X minus":



Recall that momentum in the light-like direction which becomes the short 11th dimension of type IIA string theory has the perturbative interpretation of the D0-brane charge. Because we want to keep the momentum "p plus" finite and we want to send the light-like radius R to infinity, we must also send N to infinity - and therefore all of physics of M-theory is encoded in the U(N) matrix quantum mechanics which is the dimensional reduction of ten-dimensional Yang-Mills theory to 0+1 dimensions and whose Hamiltonian is (and now I use the tag "autosize='true'" to impress Jacques Distler, hopefully it will work for non-MSIE browsers, too)



Sav also recalled how one obtains matrix string theory - the baby of mine and DVV - by compactifying one more circle in the eleven-dimensional spacetime, thereby producing a matrix model for type IIA string theory which happens to be a maximally supersymmetric Yang-Mills theory in 1+1 dimensions compactified on a spatial circle.

What about Sav's background? He compactified one more background, repeated Seiberg's procedure and obtained matrix string theory defined on the Milne space, the same space that we discussed at the beginning because of other motivations. Surprisingly, the Milne compactification breaks all supersymmetries even though the background we want to describe should have 16 supercharges. I argued that in the large N limit, the full supersymmetry should be recovered in the matrix model and Sav disagreed.

It is not quite clear whether the correct matrix model is just pure Yang-Mills theory or whether excited open string modes remain important. At any rate, Sav's lesson is that we should study open string theories on non-trivial backgrounds because they can tell us - because of open-closed dualities such as matrix theory - non-trivial lessons about the way how quantum gravity resolves cosmological backgrounds.

Techexplorer tests

This posting is an experiment. It's very likely that you won't see the mathematics below. In that case, I recommend you to

• download Techexplorer

Before you install this software, you should close your internet browser. When you re-open this page with Internet Explorer, you should click at "To help protect your security" and you should "Allow the blocked content". One of many advantages of the Techexplorer is that the source may be written not only in MathML, but also directly in TeX or LaTeX. Fine, so let me do several experiments.

First, let us write down a matrix.

Fine, now we should add a nonsensical expression with some different colors:



How quickly can I write down the CP-violating topological term of four-dimensional gravity? It is



That's enough for now. If you want to know how can you write mathematics like the equations above on your web pages, simply click "View/Page Source" and search for the word "embed" (without quotation marks). Paste the "embed" ... "/embed" section onto your web page and edit it: it is self-explanatory and the main thing inside that you will modify is a TeX source.




Unfortunately, this kind of mathematics cannot be posted as comments - neither the slow ones, nor the fast ones.

Some people may ask: am I also able to write a more difficult mathematical expression?



Well, this is what one obtains for a twistorial sum after contour-integrating. ;-)

String cosmology at Columbia

On Friday 13th, Brian Greene and Maulik Parikh at Columbia University, 120th street/Broadway in the New York City, organized the

• Fifth addition to the Northeastern conference on string cosmology

and it was a nice and successful event, I think. It's great if such an event is organized by someone who is not just a smart physicist, but also a likable celebrity. I plan to describe the lectures. For the time being, let me just enumerate them:

• Lee Smolin: Loop quantum gravity: principles and phenomenology
• David Spergel: What cosmological observations tell us about dark energy & inflation?
• Savdeep Sethi: Matrix Big Bang
• Gary Shiu: Search for realistic vacua in the landscape

Lee Smolin - LQG

I will try to minimize my comments because most readers know my opinions about LQG anyway. Lee Smolin prepared a very complete overview of loop quantum gravity. He presented the results of the work of 100+ people - one of his first transparencies contained an extensive list of 100+ LQG researchers. He also defined the symbols "R" and "S" that mean "rigorous" and "supergravity" (or more generally, "S" stands for a result that can be generalized).

Lee started with some elementary things - such as the definition of the Wilson loop. He had simplified the formula for the Wilson loop so that the astrophysicists would not be distracted by unnecessary mathematical equations. Then he claimed (...) that the LQG quantization of gauge fields works better for gravity than it does for Yang-Mills theory. He argued (...) that the background independence - whatever it exactly means - is important and realized in LQG "all the way down to the level of mathematical rigor" - a kind of phrase that appeared many times in the talk. He stated that the Hilbert space realizing some commutators (the commutator of the flux through a surface with a Wilson line is proportional to the Wilson line) is (...) unique. (You may object that the infinite-dimensional separable spaces are always isomorphic - but your objections will fail because the LQG Hilbert space is not separable.)




What about the perturbative non-renormalizability of general relativity? "Physicists will scream id they have not heard - or if they have heard but have not understood - what happens with the perturbative non-renormalizability," he said. Because I don't belong to either of these categories, I am not gonna scream right now. Instead, I will repeat what Lee thinks is an argument. He said that the non-renormalizability is an illusion because the calculations rely on two things, namely

1. smoothness of space all the way down to the Planck scale
2. local Lorentz invariance,

neither of which holds in LQG. Smolin, of course, said that neither of these things has to hold (...) in quantum gravity in general. And these two wrong assumptions invalidate the loop perturbative calculations, he believes. (Once again, I am not gonna write what are the correct answers to these questions; the purpose of this text is to summarize Lee's talk.)

LQG may be written as a topological action with constraints. At this moment Alan Guth arrived (their train from Boston had a delay). Lee Smolin also said that the methods of LQG may be (...) applied to other theories, such as "d=11" supergravity, and he has flashed a transparency with some relevant formula for 2 seconds so that it was impossible for those who have not studied this specific proposal to decide whether it was meaningful.

At that moment, the "theorem" mentioned above occured again. The theorem says, roughly speaking, that if you want to construct a particular form of LQG that satisfies some particular assumptions (all of which are false in string theory), you will find a unique Hilbert space that can be used for this particular version of LQG. Paul Steinhardt asked which theories fall into this category affected by the theorem. Lee Smolin answered that all theories including gravity with arbitrary matter in any dimension that people ever studied and so forth, but the skepticism did not diminish at all and several participants repeated the question in one way or another.

Lee explained that the loop quantization is inequivalent to the Fock space quantization. He claimed that the volume operator is well-defined (...) and contains contributions from the spin network vertices with at least 4 legs. He outlined the path-integral (spin foam) quantization, and speculated whether topology can change in LQG (without a clear answer). He listed various gauge groups that should be relevant for various gravitational theories - SO(2,1) for 3D gravity, SU(2) for 4D gravity, OSp(1/32) for 11D supergravity, and so on. Steinhardt asked whether the gauge theory description captures the higher-order quantum corrections, and there was no coherent answer. Savdeep Sethi asked whether GR may be decoupled from other physical phenomena, and there was no writable answer either.

Someone asked whether Thiemann's new version of string theory - LQG methods applied to the worldsheet - has been validated or invalidated. Lee Smolin, who had said that all string theorists should work on Thiemann's paper a year ago, realized after 2 minutes which paper by Thiemann the participant had referred to. Lee said that he was not convinced by Thiemann's work because it did not seem to contain the physics that justifies the research in string theory (such as the graviton).

Lee also mentioned that Rovelli has allegedly represented the spin foam in terms of matrix models, and listed several LQG papers whose composition seemed rather random. Someone asked whether there was a Lagrangian description of LQG and whether it was equivalent to the Hamiltonian approach - something that seems untrue because the spin foam (Lagrangian) has a discrete time while the Hamiltonian approach requires a continuous time. Lee answered they were equivalent (...) but offered no arguments.

Lee Smolin sketched how loop quantum cosmology is done, and admitted that it is technically incompatible with loop quantum gravity because the loop methods are applied to the minisuperspace truncation of gravity, instead of an analysis of the minisuperspace limit of the full loop quantum gravity which was obtained by discretizing the full gravity. He also admitted that no questions relevant for physics can yet be answered by LQG because its low energy limit is not known. Paul Steinhardt asked how can you ever try to answer anything about cosmology without knowing the low-energy limit of your theory, and I did not understand Lee's answer.

Lee then said that most important problems have been solved - the exact Hamiltonian evolution in loop quantum cosmology; its FRW limit; the absence of singularities. He also discussed antifriction and showed a formula for the LQG estimate of corrections to an inflationary formula. Most participants thought that the formula was incorrect already on dimensional grounds, and the disagreement about the meaning of some letters such as "k" has never been resolved.

Lee Smolin also discussed the black holes - everything about the black holes has been resolved in LQG, he argued, and Olaf Dreyer solved all problems about the black hole entropy, Lee said. Finally, he discussed phenomenology - the methods how to distinguish a relativistic Universe from a non-relativistic or "doubly-special relativistic" Universe proposed by LQG. It was a very nicely composed and complete talk that would have undoubtedly convinced many audiences - not sure about this one because the participants knew quite a lot about cosmology and gravity.

David Spergel - What cosmological observations tell us about dark energy and inflation?

David Spergel's talk was very interesting. The main point he wanted to convey is that cosmology is becoming a precise science - one that can explain huge amounts of data with a pretty good accuracy using a model that depends on 5-6 parameters only. In fact, the situation is the best situation we could dream about because not only we can validate the standard model of cosmology, but we seem to have a sufficient accuracy to test the predictions that go beyond this model.

This includes the questions "How the Universe began?" and various concrete questions that arise in string theory.

People are observing (or may observe) three main types of modes in the cosmic microwave background:

• scalar modes
• vector modes
• tensor modes

When you look at the scalar modes, which are the most visible ones, you can determine the power spectrum and the higher moments. You may Fourier transform the energy density "rho(x,t)" into "A(k,t)", and the simplest model can express this quantity in terms of the same quantity at "t=0"

• A(k,t) = A(k,0) T(k,t)

where "T(k,t)" is the transfer function. David Spergel emphasized that most of the volume of the visible Universe has the redshift "z" much greater than one - something that you may find counterintuitive.

The vector modes are much less known and they can arise from cosmic strings that are created according to various hybrid inflationary models. All the tensor modes are - as of today - measured indirectly, and it will be so in the near future, by

• WMAP
• PLANCK + balloons
• CMBPOL

Spergel discussed what is the maximal "l" (orbital angular momentum) that we can detect with various available tools:

• WMAP, 1 year: l=300
• WMAP, 6 years: l=600 (those six years are already planned; they are preparing the final report on the 3rd year of WMAP, and David said that people should not be impatient because an imperfect report would not help the community)
• PLANCK: l=1500
• IDEAL: l=2000 (this is the realistic maximum we can ever get)

The tensor modes - gravity waves - are always observed indirectly. He mentioned various future surveys that are intended to give us better data, such as:

• Loeb + Zaldarriaga - the measurement of galaxies of high redshift "z" much greater than one using the 21 cm line of the Hydrogen atom
• Melnick et al. - Cosmic inflation probe - the details of this project are not known, but it will probably be another observation of many galaxies
• Square kilometer array

and so forth. David Spergel said that we can measure the "10^{-2}" errors today, we will be able to do better in the future, and it is plausible to realize finite-cost projects that will measure the errors up to "10^{-6}". It will become possible to observe galaxies with redshift around "z=7". His punch line was that

• if there is a good and convincing prediction from string theory or another theory about the 10^{-5} errors, they can test them.

As you can see, this is an example where experiments are ahead of theory. We simply do not have convincing predictions for this kind of observations so far.

David said that the "low k" observations will probably never improve because there are so few of these modes. He discussed the non-gaussianities and their origin in non-linearities. He asserted that they were almost completely absent in the cyclic models, and small but non-trivial in most inflationary models. Galaxies generate non-gaussianities, too

Dark energy

Concerning the positive cosmological constant, he argued that the evidence is now very strong and comes from many sources. For example, Seljak has shown that "w" from the equation of state is most likely constant, by combining Sloan, Supernovae, and WMAP.

David showed various graphs that agree about its values. There is also strong evidence that the dark matter must be non-baryonic. What is dark energy? He sketched various recent speculations that it was not really a cosmological constant. He also addressed the anthropic explanation of the cosmological constant by a transparency informing that the best place to discuss creationist science is Kansas. (Later, he also entertained us with a story about the Spanish inquisition.) The primary measurement that determines whether the cosmological constant is there and whether it behaves properly is the function "H(z)", Hubble's constant as a function of the redshift. Note that once you measure this function, you may calculate

• delta eta = int dz / H(z)

Then it's important to know the distance which is obtained either as

• luminosity distance - from supernovae (standard candles)
• angular momentum distance, d = delta eta / (1+z)

Conclusions: Cosmology now offers not only a beautiful agreement between theory and experiments, but also the capacity to probe physics at the fundamental scale.