Gia's landscape and other new papers

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


Back to physics:

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

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

OK, my guess is that we should spend more time with Gia's landscape paper.

• http://www.arxiv.org/abs/hep-th/0410286 - Gia Dvali's anthropic solution of the hierarchy problem - There are also other interesting papers on the web, but this one, I think, will attract the attention of many people. The paper is based on Gia's previous work with Vilenkin, but this is my first encounter with these papers.
  

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

Recall that Nima and Savas have proposed Split supersymmetry

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

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

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

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

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

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

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

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

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

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

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

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

Now a generalization of the ADM mass for branes.

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

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

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

Something about mirror symmetry for supermanifolds.

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

We want more topological string theory!

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

Now a K-theory for D-branes paper.

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

Now a PhD thesis.

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

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

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

The last paper must be about twistors...

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

A reply to Osama

To begin: Peace be upon he who follow the Guidance.

• Peace be upon she who likes peace and who follows the laws of the Standard Model.
  
  

People of United States, this talk of mine is for you and concerns the ideal way to prevent another Manhattan and deals with the war and its causes and results.

• It seems that your talk was not quite addressed to people like me. It is hard to say whether someone should seriously talk to you - and the details of your speech are probably much less important than you think - but on the other hand, such a debate may have some educational value. Let me start with a trivial answer to your question: the best way to prevent another Manhattan - and to stop blackmailing like this one - is to defeat the terrorists like you, using both military as well as the help for those who need it and friendship with those who deserve it.
  
  
• A priori, another approach would be to become your friends and to fulfil your wishes, but this strategy can't work. Your demands would have no limits. Your perverse dreams are infinite, much like your, non-renormalizable edition of Allah. There is little doubt that you would like to eliminate whole countries from the map of the world - Israel, for example - and it is just too a high price to pay. It seems a more realistic approach to be brave and patient, and to try to find the murderers who have no respect to human life. I think that our civilization has the capacity to achieve this goal.
  
  

Before I begin, I say to you that security is an indispensable pillar in human life and that free men do not forfeit their security contrary to Bush's claims that we hate freedom.

• It is really ironic if you talk about security as a pillar in human life. Although you may otherwise be an irrelevant average person, your deadly ideas and your very existence has already cost thousands of human lives - not speaking about tens of billions of dollars of the US taxpayers (and some other taxpayers).
  
  
• Concerning freedom and security: it is important to realize that the very idea that a person XY would have to follow your wishes would mean that XY is not free. Freedom always means that security is not perfect. We always prefer to be free as well as secure, but sometimes, we must find a compromise.
  
  

If so, then let him explain why did not strike - for example - Sweden.

• He has already explained it in his speech on 9/11. America has been targeted for attack because the Americans are the brightest beacon for freedom. Well, this answer also includes the fact that Sweden has not been targeted because Sweden, although it is a nice and decent country without any serious problems, is not the brightest beacon for freedom. In fact, it has been a social state for quite some time, but that's a different issue. :-)
  
  
• Your speech makes it clear that you hate freedom - human rights, religious freedoms, as well as economic freedom - and you are upset if you see freedom in the USA, and you are equally upset if you see it in the Arab world.
  
  
• Well, of course, this is not the full answer. You have not chosen Sweden yet because of two more reasons: the religious situation in Sweden probably looks more satisfactory to you - Mosques are being built as the percentage of Muslims is well above 2 percent (because of immigration). Second, Sweden simply did not fit into your sick plans so far because Sweden is not too active in defending freedom throughout the world. Do you have a different explanation why you've already murdered hundreds of people in Spain and no one in Sweden?
  
  

And we know that freedom haters do not possess defiant spirits like those of the 19 may Allah have mercy on them.

• We may be using a different terminology. Let me guess that by freedom haters, you really mean freedom lovers. Be sure that freedom lovers possess at least as defiant spirits as your terrorist friends - those who are already waiting for you in the Hell. (For my fellow atheists: the word "Hell" is just a metaphor.) That's why thousands of troops from the USA and its allies risk their lives in Afghanistan and Iraq, and that's why I don't hesitate to answer your speech. But the defiant spirits are not what really distinguishes us from you - the difference is mainly in the principles of humanity, something that you have no idea about.
  
  
• Fortunately, technology is another difference between you and the modern free world. You are only able to destroy - you know how to use our airplanes to kill thousands. We are better in inventing, developing , and constructing the airplanes, and in saving the lives.
• It is people like you and your terrorist friends who prevent your part of the world - and most of the Arab nations - from joining the modern, happy, and prosperous world. You know, religion and traditions don't contradict freedom, democracy, and capitalism, as long as most people are also able to use their hearts and brains. Concerning the 19 "heroes": they're gone, and although they were murderers, I always felt a bit sorry even about them. They had to realize that their lives had no value anymore. Most likely, they also believed that they could be rewarded by Allah for their acts. Well, I of course don't believe that they will be rewarded, but even if I multiply my faith in God by one million, the Hell is the only new thing that expects them.
  
  

No, we fight because we are free men who do not sleep under oppression.

• The reason why you "fight" is that your brains suffer from a very perverse, collective disease - a disease that you're unable to distinguish from Allah. Because this disease is a threat for the whole humankind, we just can't let you propagate on the surface of this planet.
  
  

We want to restore freedom to our Nation and just as you lay waste to our Nation so shall we lay waste to yours.

• You would have to be more specific which waste are the Americans laying in your Nation. On the other hand, you don't have to explain the waste that you lay to America.
  
  

But I am amazed at you. Even though we are in the fourth year after the events of September 11, Bush is still engaged in distortion, deception and hiding from you the real cause and thus the reasons are still there for a repeat of what occurred.

• You know, that's the defiant spirit and the power of freedom. Yes, America is amazing, and despite the disaster that you caused, America has been able to keep on moving. It's because its system is based on the right values and ideas. I realize that you may still feel very important - you may start to compare yourselves to some of the most amazing killers in the history of humankind - but you should try to restrict your self-confidence a little bit. Eventually you will be found in a spider hole and treated in a similar way like thousands of other killers.
• If you really believe that someone in America - or the rest of the world - will seriously listen to your weird interpretations of 9/11 and what it means and how it should be dealt with, then you're really ill. You're nothing more than a megalomanic killer, and only the most evil and the most stupid people can provide you with support. My guess is that you are surrounded by dumb people who just say "Yes, Mr. Laden", "Yes, Mr. Laden" (including the religious titles), and this makes you increasingly disconnected from reality.
  
  

So I shall talk to you about the story behind those events and I shall tell you truthfully about the moments in which the decision was taken for you to consider.

• If I did not make an advertisement to your speech, no one would study the details of your rants.
  
  

I say to you Allah knows that it had never occurred to us to strike towers.

• It had not occured to you until you got the idea, right? The infinitesimal glimpses of conscience that you're showing are simply not enough. What you should do is to apologize and offer the rest of your life to peace and to America - the country that you've hurt so much (but not as much as you would like). I am not sure whether it would be enough for you to correct your image in the eyes of God - whichever God you have in mind - but it is your only chance right now.
  
  

But after it became unbearable and we witnessed the oppression and tyranny of the America/Israeli coalition against our people in Palestine and Lebanon, it came to my mind.

• If your personal psychological problems became unbearable in a civilized country, you would be offered doctors who could help you - and save thousands of lives. This does not happen on the Afghani-Pakistani border or where you exactly live right now. That's sad. By the way, we have a lot of physics colleagues from Israel, and they want everlasting peace to exist in Israel (and Palestine, if this country is ever created).
  
  
• The Palestinians have the opportunity to study at the universities, but their results can't compare to the Jews'. What do you think is the reason? I think that the main reason is that they have bad leaders and authorities that teach them wrong things. In some sense, you are one of these "leaders". Because of these leaders and "leaders", the Palestinians - and perhaps some other nations which are able to trust people like you - remain underdeveloped, and relatively uncultural nations that are threatening the security of other nations.
• I hope that they will eventually realize that they must pick more modern ideals and leaders, ones that are compatible with the modern civilization, and they will be living much happier lives. We're living in the same civilization that started because of many great Arab contributions several millenia ago - the Arabic numerals are an example. However, something went wrong in the Arab world afterwards, and the task for the future generations of Arabs will be to fully return their nations to the civilized world - the world that has already learned that democracy and freedom is the best known system for a society to develop.
  
  

The events that affected my soul in a difficult way started in 1982 when America permitted the Israelis to invade Lebanon and the American 6th fleet helped them in that.

• I am not a historian, and it's hard to give a balanced description of all these events. Nevertheless, it may be useful to say a couple of elementary words about the Lebanon War - more precisely about the Operation Peace for Galilee. You know that it was the same America that forced the Israeli prime minister Begin to withdraw their forces from Southern Lebanon in 1978. Osama, you're so blinded by your hatred that you're unable to see the very many examples in which Americans tried to protect peace - as well as the rights of Arabs. If the Arabs were able to respect the ceasefire etc., the war would have never started. Unfortunately, hundreds of terrorist attacks - similar to those that occur today - were taking place in Israel and on the Lebanese-Israeli border. The very specific act that initiated the war was an assasination attempt against the Israeli ambassador in the UK.
• Henry Kissinger (the former US secretary of state) said that "no sovereign state can tollerate indefinitely the buildup along its borders of a military force dedicated to its destruction and implementing its objectives by periodic shellings and raids." (Washington Post, June 16, 1982)
• I would definitely have agreed with this general statement, although it is a very controversial question whether starting the war was a good idea. At any rate, the war was some sort of "War Against Terror" in the early 1980s, and although it caused a lot of pain and it was very expensive for Israel, I feel that it meant some kind of progress because I would say that Lebanon is not the primary source of terrorism anymore, and there is more peace, at least in this part of Israel's borderland.
  
  
• However, you have a correct point - that the Jews simply do influence American policies more than the Arabs - not only because of the Israeli spy that was identified in CIA or whatever exactly happened. ;-) The Jews follow principles that are simply more compatible with the democratic system - the broadly defined system that also works in America and Israel. Be sure that the main difference between the Jews and the Arabs is not a particular difference between the Koran and the Bible. The main difference is in the way how these religious principles are interpreted are applied in the real life, and the terrorists' interpretation of the Koran is the least viable one.
  
  
• If you were able to realize that the Koran actually encourages the people to love one another and to educate themselves, be sure that the world would become much better. But you are apparently uncapable of such a phase transition. If people like you will keep on influencing Islam in the future, this religion will become a mantra of dangerous animals. If the wise people become influential, the religion of Islam may become one of the pillars of the future world.
• Do you know that the muslims used to respect the Christians as the "people of the book"? Religious tollerance and the respect for knowledge is something that has become much less important in the Arab world - and the people like you should be blamed for this unfortunate fact.
  
  

And the whole world saw and heard but did not respond.

• The whole world also saw the hundreds of terrorist acts that justified the steps of Israel. The whole world also knows that the Arab terrorists were not the first people who made the Jews suffer. The whole world also knows that any kind of intervention constitutes a risk.
  
  

In those difficult moments many hard to describe ideas bubbled in my soul but in the end they produced intense feelings of rejection of tyranny and gave birth to a strong resolve to punish the oppressors.

• This had to be a really strong feeling if you were able to kill 3000 people 20 years later because of these events from the history textbooks. The word "tyranny" in this context is weird. Poor Israel was a small, innocent, peaceful country that was being attacked by murderers like you. If the question is whether it had the right to protect itself, the answer is definitely "yes". If the question is whether it was a reasonable strategy to protect itself, the answer is "I don't know, but I also don't know of any better strategy that they could have used".
  
  

And as I looked at those demolished towers in Lebanon it entered my mind that we should punish the oppressors in kind and that we destroy towers in America in order that they taste some of what we tasted and so that they be deterred from killing our women and children.

• I wonder whether you were really the first person who invented this "great" idea. By the way, the towers in New York were much more populated (and expensive) than the towers in Lebanon, and even if your Allah were drunk, He would definitely agree that it was not a fair revenge, especially because you picked America.
  
  

We have not found it difficult to deal with the Bush administration in light of the resemblance it bears to the regimes in our countries, half of which are ruled by the military and the other half of which are ruled by the sons of kings and presidents.

• This sentence implies that you don't like those Arab regimes that resemble the American ones. In other words, you don't like the idea of democracy. It's because you know that the more democracy, freedom, and prosperity there will be in the Arab world, the less influential the sad people like you will be.
  
  

Our experience with them is lengthy and both types are replete with those who are characterised by pride, arrogance, greed and misappropriation of wealth.

• Do you think you are the right person to talk about misappropriation of wealth, greed, arrogance, and pride? You who could have used half a million of dollars from your rich bank accounts to kill thousands and cause hundreds of billions of dollars of damages, instead of investing them to something useful? Something that could actually help the people? You, a person whose life has been one big disaster, but who still wants to teach us how should we behave, wants to criticize others for their pride and arrogance? Well, let me agree that the word "greed" does not characterize you too well, except for your desire to be powerful.
  
  

This resemblance began after the visits of Bush Senior to the region at a time when some of our compatriots were dazzled by America and hoping that these visits would have an effect on our countries. All of a sudden he was affected by these monarchies and military regimes and became jealous of their remaining decades in their position to embezzle the public wealth of the Nation without supervision or accounting.

• That's ridiculous. All American leaders and most of the Western leaders would be happier if the regimes in the Arab countries - even the friendly ones - resembled the Western democracies more rigorously. But in the real world, it's not possible to have everything, and the West must choose a lesser evil.
  
  

So he took dictatorship and suppression of freedoms to his son and they named it the Patriot Act under the pretences of fighting terrorism.

• In the real world, one cannot be 100% secure and 100% free. After 9/11/2001, America (and other countries) had to realize that the unlimited freedom implied some risks to the national security. The equilibrium had to shift, and the Patriot Act is a reasonable, very small restriction of some freedoms whose effect seems to be a dramatic increase of the national security. Three years without a new major attack seems to be a good evidence that it works.
  
  

In addition, Bush sanctioned the installing of sons as state governors and did not forget to import expertise in election fraud from the regions presidents to Florida to be made use of in moments of difficulty.

• If the election fraud in a Western country were even remotely comparable to what's happening in some of the Arab countries (for example Iraq in which Hussein received 100% of the votes), that would be pretty serious. On the other hand, if the problems with the elections in the Arab world (for example, the problems that may occur in January in Iraq) were comparable to the tension in Florida, that would mean a huge victory of democracy in the Arab world.
  
  

All that we have mentioned has made it easy for us to provoke and bait this administration.

• It's apparently easy for you to kill thousands - the lives don't matter as long as you "provoke and bait the US administration", do they? You know, that's another difference between the cultures. The US president is not a second God. He or she is just one of the US citizens that has been elected to serve her or his country. No one in the civilized world will accept your explanation that 9/11 was legitimate because it is important to "provoke Bush".
  
  

And for the record, we had agreed with the Commander-General Muhammad Ataa, Allah have mercy on him, that all the operations should be carried out within 20 minutes before Bush and his administration notice.

• Yes, your "commander-general" and you were moderately skillful technically in designing this horrible act. On the other hand, NASA synchronizes various machines with the accuracy of picoseconds, so be sure that your skills won't be enough for you to find a job in the USA. The only thing that is exceptional about you is how little you care about human lives - but this is a feature that we don't appreciate too much.
  
  

It never occurred to us that the Commander in Chief of the armed forces would abandon 50,000 of his citizens in the twin towers to face those great horrors alone at a time when they most needed him.

• On 9/11, I was defending my PhD thesis in New Jersey at 9:30 am. You were unable to stop the defense either. Actually, I was only devastated after I saw the first videosequences from Manhattan on TV which was around 11 am - well, I did not sleep for several days. That's your fault, too. By the way, I hope that now you realize that you were fortunately very far from the number of 50,000 casualties.
  
  

But because it seemed to him that occupying himself by talking to the little girl about the goat and its butting was more important than occupying himself with the planes and their butting of the skyscrapers we were given three times the period required to execute the operations. All praise is due to Allah.

• You know, Bush is a sensitive person, and he just could not scare the little girl. If a disaster like that happens, he at least tried to minimize the bad consequences of your act. A scared girl would be another bad consequence. Bush did not disappoint as the leader after 9/11. Incidentally, America has a lot of security rules at all possible levels, and the US president is not necessary to start the emergency operations in the World Trade Center.
  
  

Bush and Kerry: estimates

I am not really allowed to influence politics in the USA, and in some sense it is a great opportunity to keep this blog fair and balanced - one of the very few fair and balanced blogs around. No official endorsement will be revealed in this article.



According to my private index which is a weighted combination of available indices, the support for Bush and Kerry seems to be, three days before the elections:

• 46% for Bush vs. 46% for Kerry overall; the race is dead even; Ralph Nader at 2% (less than in 2000)
  
  

The following categories are ordered from the most pro-Bush ones to the most pro-Kerry ones:

• 92% faithful Republicans for Bush
• 80% of born-again Christians for Bush
• 75% of those who changed their mind after the new bin Laden tape for Bush
• 72% conservatives for Bush
• 71% of the "Iraq war is the top issue" voters for Bush vs. 25% for Kerry
• 70% of investors for Bush
• 54% voters who regularly attend religious services for Bush
• 52% of married men for Bush
• 50% married women for Bush
• 49% men for Bush
• 44% self-identified independents for Bush vs. 41% for Kerry
• 49% newly registered voters for Kerry vs. 42% for Bush
• 53% single women for Kerry
• 57% of Northeast for Kerry
• 70% of Hispanics for Kerry
• 80% liberals for Kerry
• 84% of black voters for Kerry (was: 90% for Gore in 2000)
• 86% faithful Democrats for Kerry
• 90% of Ivy League faculty for Kerry
• 103% of anti-Bush bloggers for Kerry

The errors in these numbers are roughly 3%, which is the percentage of undecided voters. The error of the least reliable categories are biased and they can indeed reach 3%.

Women in physics

Several people, including Peter Woit (before me) and Sean Carroll (after me) wrote essays about women in physics, and because I think that this issue is very interesting (and in the American academia, it is also clouded by feminist mist and myths - which is a nice combination of syllables, is it not?), I can't resist to write something about the topic as well.

The male scientists do not have a monopoly in their fields anymore. There are fields in which the women are making more impressive contributions than men.

Also in physics, we are surrounded by many women and girls who are very smart. They can also be smart and beautiful, if you allow me to make another point. They can write papers that are more technical than the papers of their male colleagues, and they can be stronger personalities when they defend an idea. The most cited high-energy physicist in the last 5 years is female, and I am happy that her office is next to mine. The president of the APS is female, too. Marie Curie Sklodowski had received two Nobel prizes for physics and chemistry and Maria Göppert Mayer one physics Nobel prize. Nevertheless, the percentage of women in physics continues to be small. Usually we don't distinguish the physicists according to their gender - and I think that generally we should not distinguish - but sometimes it may be useful or it may be fun.



That's a good point to start. Let me redefine the word "feminism" to denote the ideology based on the assumption that females are being exploited by the males, and radical steps must be done against it. Many of us have lived in a regime based on "marxism-leninism" which is based, among other things, on the idea that the working class is being exploited by the capitalists, and radical steps must be done against it. Well, some steps have unfortunately been taken in the latter case, and many of us have had experienced the consquences.

The formulation of the previous paragraph makes it clear that I am not going to defend this type (and most other types) of feminism. Incidentally, a feminist according to my definition does not have to be female. It can be a male, but then it means that something is not right about him, I think.

Feminists also believe that men and women do not differ in any way (perhaps, some of the most realistic feminists realize that there are at least some differences related to reproductive physiology). They believe all possible types of unscientific ideas. For example, they believe that the only natural state of affairs is when males and females have the same representation (50 percent vs. 50 percent) in every single field of human activity, and anything else proves that there must necessarily be some discrimination going on.

The influence of this ideology at the U.S. academic institutions - namely the policies that try to "protect women that are discriminated" - is discouraging for several groups of people:

• first of all, the affirmative action is discouraging for the successful and talented females (or other "minorities") who want to be (and can be) equally good or better than their male (and other female) colleagues. The existence of affirmative action tells them: "If you get a job or an award, it's not quite because of your abilities and work. It's partly a bonus for your not having a penis (or for having a different color of your skin than your friend, or whatever else)." I know very many women (and members of other "minorities") who don't need any support of this sort. In fact, I would even say that every time this discussion starts somewhere, the girls who are already in physics confirm that they don't want this "help".
• the idea that the affirmative action may have been relevant for a decision creates the feeling among many people that the particular women are worse at the end, even though it is often not the case.
• the propaganda that the girls must have the same good results in physics and maths at the basic schools and the high schools causes unnecessary frustration for many of the "ordinary" girls who are really not interested in math and physics - because this propaganda makes them think that it must be their personal problem if they're not as interested in math and physics as their male classmates which is often the case.
• the stereotypes about the "abusive emotional relationships" between "senior" male professors and "junior" female graduate students, which is the usual way how the "problem" is being presented, is potentially devastating for many relationships, and it does not reflect reality too well. In general, the assumption that an emotional relationship must be "abusive" by default is just a wrong and counterproductive assumption - an assumption that effectively contradicts the presumption of innocence.

I hope that it is not such a secret - and I can tell you that my diploma thesis advisor in Prague (please don't ask me about the name, to keep it partially confidential) - whom I consider my friend, and we wrote a textbook together - married my classmate. She simply fell in love with him during the first lecture, and finally it worked out, despite the 20+ years age difference.

I personally find it disturbing if someone has the courage to publicly question their relationship just because he was a teacher and she was his student. Such a questioning simply violates what I consider to be a respect to basic human freedoms, and a respect to important relationships between the people - it's a disrespect to love itself. But of course, the "mainstream" approach to such questions depends on the culture and traditions of each country (even though I believe that there is not too much difference between the USA and Czechia at the end).

Don't get me wrong: I can imagine that there are abusive relationships, and something should be done with many of them. But it's just wrong to assume that a relationship must be like that, and it also wrong to assume that the abusing person always has the same gender and job, which is a different gender and job from the abused person.

It's also very unbalanced to create a false stereotype in which the teachers are trying to date their students, and not the other way around. I know more examples of the second category that is claimed to be virtually absent in the USA. It's very hard to believe it. Also, it is not too natural to think that it is always the males who become the abusing ones.

The myths about discrimination as the universal explanation

Now, let me say that it does not sound realistic that the girls are currently discriminated at many places if they want to become physicists. Moreover, I claim that all of us who understand how the universities work must know that no visible discrimination exists. The average girls simply do not like physics as much as many boys do, even if they are supported. It's not something that is guaranteed to be the case forever, but today it is simply an observable fact, regardless of its explanation. Most of my female classmates at the basic school and the high school openly declared that they hated math and physics, despite the attempts of the teachers to make them like the subjects. Of course, such observations have their exceptions, but I've met a sufficient number of people to claim that my statistical ensemble is large enough to start to make realistic conclusions. I am sure that most people must agree that it is true - that the girls usually hate math and physics - and the people who claim that it is not the case had to be brought up in the vacuum.

Genders have played slightly different roles in the society for centuries and millenia - but even if they did not, there are just so many biological (and biochemical) differences that a different "typical" focus of the two genders just could not be surprising.

Another factor is - and this paragraph was added later - that the boys typically have higher fluctuations from the average which implies a higher concentration at both ends of the "linear spectrum of abilities", whatever this simplified construct exactly means. This fact that the males have larger fluctuations (in their aptitude etc.) has an evolutionary explanation - the number of children that a female has is more uniform which discourages Nature from making too many experiments with the females - while, on the other hand, males can have very many (or no) children which means that "better survivors" may be generated if Nature allows the men to fluctuate a little bit more.

The male and female brain work differently in details and hundreds of differences are known. The average male brane has 20 percent more neurons than the average female brain (23 vs. 19 billion of cells, according to a certain "normalization"). The latter has more connections between the neurons than the male brain, but I can't tell you any numbers. When thinking about language, one can show (by EEG) that both female hemispheres, but only one male hemisphere, is active. The hormones influence the brain in many different ways, and so forth.

Also, one of these two brains is dominated by gray matter while the other is predominantly run by white matter. This sentence was also added later.

The expansion of the cortex has been a critical stage in the evolution of the humans. No doubt, the human cortex is much more developed than the cortex of chimps and gorillas. A related fact is that the chimps and gorillas have less than 10 billion neurons; the rats only have 65 million neural cells or so. If we talk about biology of mammals, the size of the brain does matter, and only very silly (or strongly ideologically blinded) people may argue that the size is completely irrelevant for the functioning of all brains in general.

Various other differences (hundreds of differences) between the male and female brains are known (they are related to hormone, genes, anatomy, physiology, and the early evolution of the embryos), and it seems that ordinary people know them better than many of my colleagues scientists. See, for example, the following pages:

• Brainplace.com
• Guardian.co.uk
• Betterhumans.com
• Washington.edu
• Google - brain differences

Let me point out that it may be a waste of time to talk to those people who simply believe that the sexual organs are "the only difference between the men and women" because these people have not fully adopted a scientific way of thinking. They obviously can't observe the world around, and they are unable to click at the five links above and learn the elementary stuff.

On the other hand, the number of neurons is certainly not the only factor that influences the way how a person (or an animal) thinks and how capable is she or he to perform different types of mental activity. Let me emphasize that the possible conclusions about the correlations between anatomy and mental abilities should not affect the decisions about any particular individual; we can learn much more about anyone if we talk to him or her than if we measure some physical parameters. On the other hand, these possible correlations are the necessary considerations that we must make when we try to explain some statistical data, which is necessary for rational policymaking.

Physical weakness as an explanation?

Concerning the female "weakness", I just don't buy it. The females can be equally or more powerful - sometimes even physically - as the males. I would guess that my colleague in the department who can be the toughest one in her criticism of string theorists, for example, is female. ;-) And there are other examples like that. Sometimes it is not the case, and a certain amount of aggressivity is a necessary assumption for many jobs (and unlike others, I don't think that physics is the totally best example). This will be discussed in the next section.

There may be parents who are discouraging their daughters from becoming physicists. At the end, I don't believe that most parents would become upset if their daughter is a successful physicist or engineer, for example. But even in those cases, the parents simply have the right to try to influence their daughters (and sons) within the mantinels defined by the law. Being a parent of someone is not something that you can just ignore. And the daughters and the sons have the opportunity to disagree and revolt. And many do.

Arrogance, aggressiveness, competitiveness

Some people try to argue that it is not a real discrimination but rather the atmosphere of competitiveness, arrogance, and aggressiveness that discourages young women from becoming physicists. Well, the following comments come to mind:

• physics is certainly not viewed as the most aggressive, arrogant, and competitive field by the general public. In fact, just the contrary is closer to the truth. The mathematicians (and physicists, for that matter) are viewed as "sissy". No doubt, politics, wrestling, and other sports are examples of human activities that are viewed as much more aggressive and competitive.
• there is no hard evidence that the women would be more discouraged by these three things than the men. Many women are attracted by aggressivity, and so forth.
• on the other hand, these three things, at least in some concentration, are often important for the development of the field, and it is certainly not only true about physics. One can eliminate competitiveness, for example, but this is more or less guaranteed to reduce the efficiency. Is the balanced percentage of different groups more important than whether we will be able to find the truth? I don't think so.
• physicists, especially the theoretical physicists, often use big words to explain the role of their field in the scheme of things. The main role of theoretical high-energy physics, for example, is to reveal the most fundamental rules that underlie all phenomena (or at least, as many as possible) in the Universe and their mathematical encapsulation - and this quest is obviously more intellectually demanding and important than feminist studies, for example. Alan Sokal has shown that whole fields in social science are pure rubbish, and a physicist who knows why he chose his or her field will agree.
• if someone does not like this description of hierarchy in science because it is "arrogant", he or she should not have chosen theoretical physics. If the understanding of the role of theoretical physics as above is how "arrogance" is defined, then "arrogance" is an important feature for a theoretical physicist, I think. We study the field because we think that it is important and it excites us, and if someone finds it unimportant, she or he should choose a different field. Why? It's not just because she or he can contribute more in the other field, but she or he will also feel more satisfied with her or his own work.
• yes, this feeling of the importance of our field and our work is analogous to other feelings in other fields (including wrestling, and the number of push-ups, and other examples by Sean), but this means no problem for the society that "smears out" these different viewpoints. Also, it is important that some people are able to argue and decide which activities are important - otherwise there would be no tools to decide how various fields should be funded, for example.
• I see the exactly opposite problem than the "problem" described by Sean, for example. Current string theorists and physicists in general are just too "nice", and this atmosphere is correlated with the reduced amount of progress that we're doing (whichever is the cause vs. the effect). I know that Nima Arkani-Hamed agrees with me, for example, and the people who say the opposite statement seem to be disconnected from reality.

Summary

The affirmative action - or the positive discrimination, as we call it in the EU - is not right. It does not really help, and it is not fair. Its goals are based on scientifically unjustified, arbitrary assumptions. It creates bad feelings, stereotypes, and havoc in many decisions. Women have had the same rights (in almost all aspects of life where it's possible) as men for quite some time. Talented female mathematicians and physicists, such as Emmy Noether, have already been able to succeed 100 years ago. In Noether's case, it is David Hilbert, not the feminist movement, who can be credited for making sure that all conceivable prejudices were irrelevant already in 1907.

There will always be some differences between the genders, I think and I hope, and it's time to stop inventing ghosts that are supposed to be hurting the women behind the scenes - because the real consequence are antighosts that are hurting the actual women in reality, and the only difference between a ghost and an antighost is the sign of the ghost number.

Note added later: If you want to see a reaction of an actual self-identified feminist, click here. Obviously, there exist different opinions about this issue.

The author argued that Sean Carroll has beautifully explained that the physicists are - let me paraphrase it - arrogant white male assholes (congratulations, Sean!), and she calls for a cultural revolution in physics. Also, she effectively admires her feminist movement for having discovered the localized gravity and warped geometry.

Also, she argues that Lisa Randall is definitely too old and she definitely could not study at a good university. If she used the internet search engines, she could have found out the Lisa is not that old and that she received her PhD as well as BS from Harvard which is not such a bad school.

Lee Smolin: The Trouble with Physics: a review

See also a review written by someone else

Lee Smolin: The Trouble With Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next - (Hardcover)



Another postmodern diatribe against modern physics and scientific method (2 stars)

The interactions between Lee Smolin and mainstream physicists are interesting. Lee often visits us. We smile at each other and Lee is being politely explained why his newest theories can't really work. Lee says that he understands these arguments. Then he returns to a conference or a journalist and repeats that all of his theories have been perfectly proven, while offering even more unusual theories. The newest theory says that the neutrinos are octopi swimming in the spin network. Believe me, we like him but it is not always easy to take him seriously.

A few months ago, I had to promise Lee that I would read the whole book before saying anything about it. So I did so. It was tough because the concentration of irrational statements and anti-scientific sentiments has exceeded my expectations. The book is primarily filled with the suicidal and absurd sentiment that all of modern physics of the last 30 years - the era of Lee's career - is a failure. The first part of the book tries to focus on technical aspects of string theory. The second part of the book offers a postmodern view on the scientific community and some radical proposals how to fix the "problems" that the author has identified.

As far as I can say, everything that tries to go beyond the existing popular books is unreasonable with one possible exception, namely some of Lee's general ideas about the anthropic principle.

What are the problems with Lee's appraisal of physics? First of all, Lee reveals his intense hostility against all of modern physics, not just string theory. He believes that quantum mechanics must be wrong at some fundamental level and many people should try to prove it. He also believes that the attempts to falsify the theory of relativity are among the most important topics to work on. In the context of string theory, he literally floods the pages of his book with undefendable speculations about some basic results of string theory. Because these statements are of mathematical nature, we are sure that Lee is wrong even in the absence of any experiments.

For example, he dedicates dozens of pages to speculations about the divergent amplitudes at finite orders of the perturbation theory - amplitudes that have been proven to be finite. He also proposes that the AdS/CFT correspondence and various other dualities are wrong. In doing so, he ignores thousands of papers that lead to the opposite conclusion. Instead, he applies the methods of creationists and invents a "strong" and "weak" version of Maldacena's equivalence. There are also frequently repeated speculations that string theory and M-theory don't exist and many other similar "ideas", together with the most popular myth that string theory can't be experimentally tested. Neither of these things is supported by any results in the scientific literature, not even Lee's own results, and most of them contradict what we know. I am afraid that it is fair to say that Lee is trying to sell things that could never be bought by the experts because he knows that his lay readers won't be able to tell the difference between a result and a nonsense.

More generally, Lee proposes a truly radical thesis that it is wrong for mathematics to play a crucial role in theoretical physics. This meme is repeated at many places and it is later used as a criterion to hire physicists. He also blames the "failures" on the culture of particle physics that has already existed before string theory. For example, we learn that when Lee Smolin studied at Harvard, he was disappointed by Coleman, Glashow, and Weinberg who were "nothing like his heroes". Wow. The reason why they were nothing like his heroes was that they preferred calculations over philosophical speculations. Needless to say, Smolin would be disappointed by Einstein and Bohr, too, because they couldn't stand scientifically unjustifiable philosophical speculations either. No real physicist can.

Two decades ago or so, Lee was also disappointed by his peers who were excited by calculations in supergravity. He also denies the difference between renormalizable field theories and the rest, and so forth.

In the sociological part of this book, Smolin complains that no one takes him seriously and tries to paint the mainstream physics community as a group of evil people. Also, he proposes "cures" for the things that he views as "problems". This includes new ethical standards of the science community. For example, one of his rules says that the conclusions must be accepted by everyone if their author is a person of good faith. Another rule, apparently applied to the other theories of the "infidels", says that they must first present a full rigorous proof.

These and other proposals are clearly meant to transform the scientific community to a dogmatic, non-mathematical, and irrational institution with double standards that is similar to the Catholic Church in the Middle Ages. He realizes that what he has defined is a church or a sect, so he tries to correct this problem by enumerating a few features in which science and religion are supposed to differ. In my opinion, neither of these things has anything to do with the main differences between science and religion.

The main difference between religion and science is that science will never accept Smolin's ideas about the scientific method. Science will never introduce Lee's proposal of affirmative action for those who are not able to fully learn the current picture of reality as painted by physics - people whom Lee Smolin misleadingly and automaticaly promotes as "original thinkers", without any rational arguments. In reality, gaps in mathematics are something very different from originality; in fact, these two things are negatively correlated, not positively. Lee doesn't want to see the difference.

Also, science will never give up the principle that falsified conjectures (even those from the people of good faith) must be abandoned - a principle that also strikingly contradicts Smolin's thoughts about the democracy of ideas. Science will never abandon solid and quantitative arguments and it will never replace them by vague linguistic games that Lee Smolin prefers. And it will never accept Lee's recommendation that the scientists' opinion should be manipulated by the ideological goals such as Lee's "diversity of ideas" by which he really means the narrow-mindedness of those who lack the imagination to learn the diverse insights offered by string theory.

The postmodern attack against science has had many forms. Evelyn Fox Keller, a professional feminist critic of science and the key supporter of this book, was at the beginning. If you want to see how serious threats the very basic principles of science will probably have to face from within, read this strange book that I rated by 2 stars because of its unquestionable ability to make you angry (and make young science fans frustrated). Unless science is going to be destroyed, it will continue to ignore Smolin's hints, despite the alternating good years and bad years. It will build on results that work and not on those that don't work, hire people who know what they're doing and not those who don't, and allow them to reach their own conclusions instead of telling them which opinions are sufficiently "diverse". Also, the role of mathematics and string theory is bound to increase, regardless whether Lee Smolin will convince his readers otherwise.

See other articles related to Lee Smolin on this blog. See also a deleted review of Non-String Physics Grad Student.

At this place, we originally had an article about an entirely different topic:

Red Sox rule

I am not exactly a baseball fan, but because the Boston Bloody Socks defeated the St. Louis Cardinals and won the "World Series", there should be an article about this overwhelming success. The last triumph of Boston like that was in 1918 against the Chicago Cubs. Great.

In the last couple of weeks, everyone who came to Harvard - Seiberg, Cohen, and so forth - were delivering us (more precisely, to the local patriots) congratulations, and because I have really nothing against the New York Yankees, for example, I did not care at all who would win. But did not they already win the World Series, I was asking?

Of course, the answer was "No", and the car horns that have dominated the acoustic waves in Cambridge since the midnight (simultaneously with people yelling and screaming) have proved that the final night was the last night. Well, I had a good opportunity to check that I had not lost the ear plugs - and they worked fine! :-)

Nissan and strings behind harmonic oscillator

Nissan Itzhaki just spoke about their paper with John McGreevy



http://arxiv.org/abs/hep-th/0408180



It's a funny toy model that relates three theories:

• the free matrix model for a single hermitean N x N matrix with a harmonic oscillator potential
• the free fermions, and excitations of a Fermi droplet which are chiral bosons
• a crazy dual string theory

Let's start with the matrix model. It is a quantum mechanical model with the Lagrangian Tr(D_t(X)^2 - X^2), roughly speaking. Because its U(N) symmetry is gauged, we require the physical states to be U(N) invariant.

Nevertheless, it is a free theory that we can easily solve. There are N^2 harmonic oscillators, they have some ground state, and they can be excited by the matrix-valued creation operators. In order to get gauge invariant excited states, we must combine the creation (and perhaps annihilation) operators into traces. It's a simple combinatorial task to see what happens. Most of the traces are linearly dependent, at least if they ask on the gauge-invariant Hilbert space.

An alternative solution is provided by free fermions. Because the wavefunction is U(N) invariant, it depends on the eigenvalues only, and using the Vandermonde determinant redefinition of the wavefunction, the system may be converted to free fermions in a certain phase space; the coordinates in the phase space are the eigenvalues of "x" and its canonical momentum "p". The fermions tend to fill the interior of a disk in the phase space and form a Fermi droplet.

One can study the perturbation of the Fermi surface (a wiggly disk), and these perturbations rotate in the clockwise direction - it's the usual rotation in the phase space of a harmonic oscillator. Therefore, they are some sort of chiral bosons, and these chiral bosons may be related to the creation operators above, and some of these relations seem to be relevant for a less trivial case of M(atrix) theory that I'm now trying to solve in a different way.

Of course, the most nontrivial side of this "triality" is a string theory, and I am still not following what the string theory exactly is. At any rate, it has an imaginary time-like dilaton gradient in the periodic time dimension (it's something that I believe is relevant for one of my long-term projects related to N=2 and N=(2,1) strings on del Pezzo surfaces as a theory of everything, and a similarity like that is encouraging). That string theory, conjectured to be dual to the simple matrix harmonic oscillator above, has some strange behavior of the amplitudes - for example, they truncate at some genus - and because I don't really understand it too well (and what it's good for and in what sense it's unique), we will have to refer to the original paper, if you're interested.

A phony hockey stick?

Willie Soon of Harvard University, one of the global climate experts among the astrophysicists, informed me about their new article

• Willie Soon, David Legates: Is the hockey stick broken?
• See also: Climate model proves erroneous

They describe a new paper by Von Storch et al. that was published in a recent (September 30th) issue of Science. The German journal Der Spiegel (The Mirror) made an interview with Von Storch on October 4th, 2004. Von Storch said something along these lines:

• The assumptions that have led Mann, Bradley, and Hughes (MBH) to their "hockey stick graph" in 1998 and 1999 are unacceptable. Their method is wrong - in fact, it's rubbish.

That's a blunt formulation and one is naturally cautious about it, but it seems that this formulation is justified. It may be useful to say what the "hockey stick graph" means. Try to draw the graph of the "global temperature" as a function of the date - between the years 1000 and 2004. What graph will you choose if your results are supposed to support the statement that the world economy and our breathing should be slowed down because these processes create too much carbon dioxide which leads to an unacceptable and unprecedented global warming?

Well, of course, you will draw a constant function between the years 1000 and 1900 (long, stable shaft) and a quickly increasing temperature between 1900 and 2000 (it's the blade of the hockey stick). Such a profile will prove that the changes are caused by the humans, and they are undisputable and potentially disastrous. That's roughly what MBH did, and they became famous for their result. Their graph was reproduced by the global climate committee of the United Nations (IPCC, Intergovernmental Panel on Climate Change) and it became one of the justifications of the process that culminated with the Kyoto protocols.




Of course, MBH also had a scientifically impressive method based on the principal component analysis. It was really the paper by Ross McKitrick and Stephen McIntyre - the so-called "audit of MBH" - that helped me to understand the methodology of MBH a bit better. I've already written an article in which I stated my opinion that this method may be a good one to isolate a picture that is covered by dust, but in order to estimate the past temperatures from shaky proxy data, it may be better to simply take the average of all the known data - the same average that the kids learn when they're 8 years old. It seems that this simple opinion is becoming more influential.

Von Storch et al. showed that the method of MBH is suspicious, using a kind of sensitivity test. In fact, I would say that MBH themselves should have done such a sensitivity test before they published their paper. How did Von Storch et al. do it? They simulated an artificial world, and extracted the fictious "proxy data" (the widths of tree rings etc.) from this model, and added a reasonable amount of random noise. In their virtual world, they knew perfectly what the "true temperatures" should be. Afterwards, they inserted the "proxy data" to the formula of MBH, and used that formula to reconstruct the temperatures. The result was very different from the "true temperatures". Quite generally, the method of MBH seems to reduce the temperature fluctuations in the past (before the thermometers were known).

What does it mean? Well, most honestly, it means that we know very little about the historical temperature record. However, if the fluctuations were greater than what MBH argued (by a factor of two or more), then the temperature growth in the 20th century is not so exceptional. People used to think that there was a medieval warm period (MWP), followed by a little ice age, and these old theories may stage a comeback.

The importance of the carbon dioxide

I've never understood the hysteria behind the concentration of CO2 in the atmosphere. CO2 is an important gas - it's produced when we breath, and it's necessary for photosynthesis. Animals produce it, plants consume it. The existence of CO2 proves that there are either animals, people, or machines around, and the growth of the concentrations of CO2 is known to be correlated with the growth of the gross domestic product (GDP). Well, CO2 may be used as one of the indicators of life and working economy.

Is it a poison? Well, I don't think so. CO2 is not quite the same thing as Mercury, for example. ;-) Should we really worry if the human civilization doubles the concentration of CO2 in the atmosphere? Today, the concentration is below 400 ppm ("parts per million"), which means less than 0.04 percent. The concentration of CO2 in your bedroom is probably much higher. Does it really matter whether the concentration in the atmosphere is 0.03 or 0.05 percent? Should we pay trillions of dollars just to avoid this increase, even if we don't know any clear negative consequences of such a growth?

Well, CO2 is known to protect the Earth from cooling, it's a greenhouse gas. Well, it's not the only greenhouse gas, and on the other hand, there are also other compounds in the atmosphere that tend to reduce the temperature (aerosoles, for example). We may ask a simple question: Is it better to heat the planet up, or to cool it down? Imagine that an observable called "the global happiness" is a function of the "global temperature". An interesting question is what's the derivative of "happiness" evaluated at the current temperature. If it's zero, than up to the first order, it does not matter whether the temperature goes up or down. If it's nonzero, there is 50% probability that it is negative, and 50% probability that it's positive. The expectation value of Delta(happiness) is zero. But of course the expectation value of "Delta(happiness) squared" is positive, and it grows with "Delta(temperature) squared". Do you think it is reasonable to pay 1 percent of your GDP for the chance that Delta(happiness) squared is likely to be a bit smaller, even though you can't predict the sign of Delta(happiness)?

I think that such a decision is an economic stupidity, especially because I tend to think that the derivative of the happiness with respect to the temperature is positive. ;-)

There are many other things whose concentration increases drastically as a result of human activity. The Aliens who observe our Solar system in the microwave range of the electromagnetic spectrum see a pretty bright star - the Earth. Humans have obviously increased the concentration of radio waves and microwaves emitted by the Earth by several orders of magnitude. Should we be worried about the unpredictable consequences of this unprecedented growth of the concentration of something? I don't think so. Experimentally, it seems pretty clear that the microwaves don't imply a disaster. We're not gonna ban radios, TVs, and cell phones because of some uknown hypothetical threats. Is the situation of the carbon dioxide really so different?

Or is the war against the carbon dioxide a simple manifestation of anti-civilization and anti-American emotions?

Dinner for Marvin Cohen

This is an experiment: I want to check how dramatically the quality of my essays - and my ability to find the correct words and the right keys on the keyboard - decreases after five glasses of wine. I am neither able to walk straight right now nor finish the preparations for the String theory lecture tomorrow (about the BRST and old covariant quantization of the string), but the current amount of self-control may still be enough to write an article onto this blog. ;-)



I've just returned from a dinner to celebrate Marvin Cohen, who is now the Loeb lecturer. There were roughly 50 people who attended the dinner. It seems that I was the only unimportant person participating, and therefore I recycled the tag "Prof. Motl" from the faculty lunch that was held yesterday. More concretely, I was probably the only person under 45, and most of the time, I was also the only person under 65 inside the 3-meter vicinity around me. ;-)



There have been many really great people who attended the dinner: Sheldon Glashow, the Nobel prize winner for the electroweak theory; Irwin Shapiro, who has made the famous experiments to verify general relativity; Eric Mazur; John Huth; Sekazi Mtingwa; Isaac Silvera; and I could enumerate roughly 50 more names like that.



Fortunately (or unfortunately), we did not have the opportunity to discuss string theory and its role in the structure of physics with Shelly Glashow (or his wife). :-) Instead, we discussed (with various people) the issues about the Casimir force (vs. the van der Waals force) and its QED or molecular explanation; KGB and the US post office - the two biggest bureaucracies in the world :-); the Red Socks and their recent victories; questions for Mikhail Gorbachev that were asked by Irwin Shapiro sometime in the mid 80s and Gorbachev's answers; the reasons behind splitting Czechoslovakia and its consequences; the different nationalities that the citizens of Ruthenia tried in the 20th century; Richard Feynman on the 1955 conference about general relativity in North Carolina; Shapiro's childhood in Far Rockaway, New York, near Feynman's house; John Edwards as a guy from North Carolina; the religion of the people who support George W. Bush and who believe that Hussain's Iraq was behind 9/11; why the people of different political orientations should listen to each other; what we did on 9/11/2001; the difference between the Russian cities of Sverdlovsk and Smolinsk. Well, you can imagine, a lot of fun stuff like that has been pondered.



It may be the right time to go to bed now, and hope that tomorrow we will do much more serious stuff than today. Well, let me admit that the significant part of this day was spent by arguments with Peter Woit about the history of interactions between mathematics and string theory. When I am under the influence of alcohole, it's easier to admit that it's probably not the most constructive way to spend my energy. :-)

Beauty, Fields medal, Witten, and Woit

I've sorted the keywords in the title alphabetically.

After Peter Woit read my words about the beauty of string theory, he wrote his own essay about beauty and string theory. If even Peter Woit meditates about the beauty of superstrings, it proves that we're definitely making some sort of progress, at least in the P.R. business! :-)

Note added later: After Peter Woit looked at this page about the links between mathematics and string theory, he wrote his own version of history of topological field (and string) theories. His picture of the history has one serious problem: it ends in 1989, and no newer insights are taken into account. Why is the end of history exactly in 1989? You might think that it may be related to the collapse of communism. Well, that's not the real reason. You will understand the correct explanation why the history of maths and physics after 1989, according to Peter Woit, does not exist, if you look here.

Let me now return to Peter's first article about the beauty of string theory. He divides the problem into five main categories:

• The beauty of symmetries - Peter Woit realizes that spacetime symmetries seem to be derived concepts in string theory. He nevertheless understands why they're beautiful, and we would probably agree about this point
  
• Miraculous nature of cancellations of anomalies and inconsistencies - his example is the Green-Schwarz anomaly cancellation, but I was thinking about a much more general set of ideas. It's not just the usual type of "anomaly" that must cancel for a theory to make sense, and the spectrum of different details that happen to work (and have to work) in string theory is much broader
  
• Uniqueness of the theory as a description of the real world, including quantum phenomena and gravity - which includes the absence of adjustable non-dynamical continuous parameters
  
• String theory as the extension of quantum field theory - Peter realizes that string theory is the only known framework that is able to go "beyond" quantum field theory, without spoiling its essential good features
  
• Beautiful connections to new pure mathematics - Peter says many incorrect things which I will correct below
  

I don't really think that Peter reproduced all the main points of my essay. He picked the advantages of string theory, but not necessarily those that would normally be associated with "beauty". The true emotion of "beauty" also follows from some properties of the theory that Peter Woit neglected: for example, its ability to regularize any singularity, and to make everything smooth.




One can find many limits in string theory - situations, solutions, or points in the moduli space - where it naively seems that singularities and infinities start to develop. String theory always offers (and predicts) new objects or phenomena - wrapped strings; wrapped branes; infinite tower of new states that "smear out" the spacetime at short distances; enhanced gauge symmetries; new light states in general; non-commutative geometry; worldsheet instantons, and so forth - and these new objects or phenomena imply that physics continues to be completely controllable, predictable, and smooth. That's a beautiful interplay of all the players - something that is necessary to avoid many otherwise conceivable disasters.

But let's say a couple of words about the last point - the relations to mathematics. Peter Woit speculates that string theory "has been an utter disaster for theoretical physics". Well, most of us know that it is nonsense and we know why Peter Woit likes to say this nonsense.

String theory and its links with mathematics

But he also writes many more specific statements that are not true. He admits that many interesting things come from two-dimensional conformal field theory. Well, perturbative string theory is nothing else than a sophisticated application of the important tools and theorems in two-dimensional conformal field theory. Consequently, it would be very hard for Peter Woit or anyone else to argue that the developments in two-dimensional conformal field theory have nothing to do with string theory.

But the last two sentences of his text may be even more problematic. He claims that it is quantum field theory, not string theory, that has had this huge impact on mathematics. He even says that Witten's Fields medal was "not for anything he has done using string theory".

Well, Peter Woit is not right. Let's start with topological string theory and the Fields medal because this is the most obvious way to show how much wrong Peter Woit is. A paper that Peter Woit believes is behind the Fields medal is

• Edward Witten: Quantum field theory and the Jones polynomial

Which quantum field theory is discussed in this article? Well, it is not the gauge theory that Peter Woit thinks about - a type of gauge theory that is disconnected from string theory. Witten's gauge theory is a three-dimensional one made out of the Chern-Simons term only - nowadays, this theory is called the three-dimensional Chern-Simons theory.

The paper using the three-dimensional Chern-Simons theory was published roughly one year after another important paper in which Witten established topological string theory:

• Edward Witten: Topological sigma models
  

Well, the three-dimensional Chern-Simons theory is the worldvolume theory of the D-branes in the topological A-model - which is the A-version of topological string theory. Such links are not just curiosities. When Witten was writing the paper, he was using many notions that became a part of topological string theory some time after Witten published his paper (well, after Gopakumar and Vafa; and Ooguri and Vafa had had their say). If you read the abstract of Witten's paper about the Chern-Simons theory (open the scanned version...), you will see that the last sentences mention some unexpected relations with two-dimensional conformal field theory. What is this two-dimensional conformal field theory? Well, it's the Wess-Zumino-Witten model which is now an important ingredient to construct string theory in the NS5-brane backgrounds, and in other contexts.

Later, another 1+1-dimensional conformal field theory was found to be closely related to this three-dimensional Chern-Simons theory, namely the worldsheet theory of the topological string.

Note added later: Incidentally, I said that "Peter Woit believes that Witten has received the Fields medal for that paper" because the correct answer is different: Witten received his Fields medal mainly for

• his proof of the positive mass theorem, based on supersymmetry (certainly something rooted in reasoning related to string theory; finally, Peter Woit hates supersymmetry nearly as much as he hates string theory, so it does not make much difference)
• his paper on supersymmetry and Morse theory (the same comment applies)
• his work on the Jones polynomial from the Chern-Simons theory
  

I am not the best person to talk about the history of topological string theory, but be sure that the reasoning that led to Witten's insights was rooted in something that is viewed as a part of string theory. Well, at least sociologically - you don't need to be a rocket scientist to see that topological string theory is studied by people who are called "string theorists" and who are interested in other parts of string theory, too. ;-) No doubt, there are many relations between the "physical string theory" and "topological string theory".

You know, a similar story can be said about most of other ways how theoretical physics influenced mathematics in the last 20 years. If you say that these influences were really influences of quantum field theory only, you really misunderstand the situation; you misunderstand what "string theory" means.

Today, we still don't know the universal principle behind string theory. Nevertheless, we're able to study string theory using many different techniques. But it is important that all these known techniques are based on quantum field theories in various spaces. It's important that these spaces are not necessarily the spacetime itself - the relevant quantum field theories may describe the worldsheet or worldvolume of strings, branes, and other objects. These spaces may become boundaries of the spacetime, and so forth.

The whole perturbative string theory is usually computed using a sophisticated and unusual treatment of two-dimensional conformal field theory. The S-matrix in spacetime is calculated as the correlator of "vertex operators" - operators associated with the external string states - integrated over all possible Riemann surfaces (worldsheets) into which these vertex operators can be inserted. Two-dimensional conformal field theory is a quantum field theory.

The AdS/CFT correspondence describes the exact stringy physics (a stringy extension of quantum gravity) in the (d+1)-dimensional anti de Sitter space as a conformal field theory in d dimensions. Again, this conformal field theory is a quantum field theory.

Also, Matrix theory describes physics at some backgrounds of string/M-theory in terms of a quantum field theory (or quantum mechanics, which is nothing else than a 0+1-dimensional quantum field theory) on some auxilliary space.

An off-shell approach to string theory, called string field theory, is a generalized quantum field theory in spacetime with infinitely many (component) fields. Moreover, string theorists systematically use effective field theories in spacetime, and effective field theories on the branes (as low-energy approximations). Even more exotic theories, such as the (2,0) theory or non-commutative Yang-Mills theory, can be viewed as generalized quantum field theories.

What I want to say is that all approaches to string theory that we know of today are based on quantum field theories in various spaces. What's "stringy" about them is the way how you use these quantum field theories, how you relate them, and how you interpret them physically. This also determines what the relevant and interesting generalizations are, and so forth. The "real" string theory is a set of ideas that tell us which quantum field theories are interesting, and what new, physically interesting behavior these theories give us. String theory also teaches us about hundreds of non-trivial connections between these quantum theories. These are theories whose properties are always described by a sophisticated application of quantum field theory.

String theory implies new ways to think about quantum field theories, and it has allowed the physicists to derive many unexpected properties of quantum field theories.

Once again, string theory, as we know it today, is the "spirit" that organizes the insights about different quantum field theories. We definitely think about string theory as something that is more general than quantum field theory, but every time we want to describe this more general structure quantitatively, we use the tools of quantum field theory (usually QFT in other spaces than you would expect).But we still have the full string theory and its logic in mind.

It is this "spirit" that was important for Witten to make most of his important insights that affected mathematics. It is this "spirit" that Seiberg and Witten had in mind when they were solving the N=2 supersymmetric theories in four dimensions. They did not write down that they were solving a problem rooted in string theory - because they did not want to lose the citations from the colleagues who would never cite a paper with the words "string theory" in it (except for your papers, Peter).

Nevertheless, it was string theory and its "spirit" that led them to this solution, too - and the connections of the followups with string theory are much more obvious and much more difficult to hide. Moreover, there are many other obvious ways how string theory influenced mathematics, and Peter Woit does not want to see them. Some of them are related to mirror symmetry - a mind-boggling relation between two apparently different six-dimensional manifolds that was first found in string theory, but it has also allowed to find many theorems in pure mathematics.

An alternative conclusion

Even though I was explaining that string theory is technically a conglomerate of "quantum field theories" in various spaces with some new ideas how to organize their observables, I believe that eventually we will find a completely new formalism that cannot be reduced to any specific quantum field theory.

Marvin Cohen, nanotubes, and space elevator

Marvin L. Cohen gave the first Loeb lecture at Harvard, and I liked it. The Loeb lecturers are always very special people - very respected physicists and physicists with exceptional skills to present their subjects. Brian Greene was the Loeb lecturer in the spring.

Cohen is a condensed matter physicist, and he decided to present

• The Standard Model of Solids

As the president-elect of the American Physical Society (who will probably replace Helen Quinn, our fellow particle physicist, if I understand it well), he had to start with two commercials.

• One of them was the World Year of Physics 2005. The next year will be celebrated as the international year of physics because it will be 100 years from Einstein's miraculous April 1905 in which he discovered special relativity, the theory of photoelectric effect, and the theory of the Brownian motion, among other things. Cohen's main goal associated with WYP 2005 is to attract many 10-year old girls to physics.
  
• The second commercial was about his plans to reorganize APS. If I remember well, Cohen divided APS into four sections: old-fashioned physics (atomic, molecular, optics); astro-particle (which probably include things like string theory); condensed matter physics; plasma and non-linear physics

I did not make any notes, but let me reproduce some of his points about APS. The "classical" section of APS (atomic, molecular, optics) is doing very well. A significant fraction of astro-particle is about the search for a TOE, but also about the Big Bang. Plasma physics continues to develop thermonuclear fusion reactors. And condensed matter physics, which is the largest portion of APS, is disorganized because it develops into too many directions.




Many people who know a lot about science as well its sociological structure and visions start to agree: the interdisciplinary topics in condensed matter physics start to dominate. Biophysics and nanotechnology start to be the most important applications of condensed matter physics - which means, in a sense, that the physicists are moving towards biology, and we must live with that. The task is to preserve the exceptional role of physics among sciences - the role of the most rigorous natural science.

Most of his talk was about physics, of course. He quoted Dirac in 1929 who declared something along these lines:

• A great portion of physics and all of chemistry can be now reduced to known fundamental physical laws, and it is just a matter of technical difficulty to obtain any results we want.

Cohen showed himself as a reductionist who is simultaneously an emergent person. ;-) Obviously, unlike many of his condensed matter colleagues, he has no problems with the idea of reductionism, and he showed us many examples of the things that have been understood and "reduced", especially if you use the right approximations (pseudopotentials, and so forth).

Take superconductors. It is still believed that all of them are sort of related to BCS superconductors - they are governed by pairs of electrons. If one electron loses momentum (by a collission with an impurity), his partner is still forced to react in the opposite way, and therefore no energy is lost. OK, there are speculations that there can exist other types of superconductors, but nothing conclusive.

It seems that the experimentalists are much ahead of theorists in condensed matter physics. All major new phenomena - such as superconductivity - were first discovered experimentally.

I can imagine that this will change sometime in the future - particle physics is currently just in the opposite situation, because the experimentalists just cannot find anything that the theorists can't predict. Cohen showed how all possible crystallic and superconductive phases of sillicon can be understood, more or less from the basic theoretical principles. Sillicon as a superconductor had a simple, roughly spherical Fermi surface, and therefore it was the first one that was understood. (The first observed superconductor was Mercury, however.) Nevertheless he showed another superconductor, something like MgB_2. Its Fermi surface is composed of four sheets. Nevertheless, today it is probably understood even better than Si, and the pictures looked convincing!

Most of the talk was about nanotubes and their applications, and they were very interesting. Because I must also do other things, let me be sketchy and choose just a couple of examples:

• Nanotubes are very thin tubes whose thickness is as small as tens or hundreds of nanometers
• Nanotubes have been seriously proposed as a material to build a "space elevator" - a kind of rope that will be hanging from the skies. You will be able to climb to the outer space, if you wish ;-)
• Four wine bottles filled with nanotubes, if properly organized, will have greater memory than all human brains in this world altogether - an interesting research direction is to construct computers and memory chips based on these objects
  
• Nanotubes may be inserted into one another, and you can build a nanomotor - a motor that rotates whose size is smaller than the radius of a typical virus
• Nanotubes, if inserted into each other, exhibit friction - the question what does the energy dissipates into is sort of entertaining and possibly deep because there are not too many available degrees of freedom

Marvin Cohen will continue on Wednesday and Thursday, but I am afraid that there are too many other things I must do and attend.