## Saturday, March 19, 2005 ... /////

### Sidneyfest

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Arthur Jaffe and Barbara Drauschke organized a magnificent conference at Harvard - informally called Sidneyfest - to thank Sidney Coleman for everything he has done and he has been for physics and the physicists. Sidney, whose health is unfortunately not as good as we would wish, partially because of the Parkinson disease, has been a great physicist, an excellent teacher with unlimited patience, an eccentric human being, and a neverending source of jokes.

He has also played the role of Wolfgang Pauli of his generation; he liked to disprove ideas, and he was also a genius in explaining things to others. We have heard numerous stories about Sidney Coleman. Unfortunately, this article can only cover a tiny fraction of the stories and comments. Many participants told me that they visit this blog, and it's not impossible to imagine that some of them will write some interesting comments.

Message for all the usual suspects who like to argue with me: try to realize that your (and our) texts are being read at least by five Nobel prize winners and several other exceptional people. ;-) I will try to appreciate this fact, too. At least sometimes.

At any rate, the conference has been an exciting testimony about the heroic period in high-energy physics - the 1960s and the 1970s, roughly speaking - in which the physicists were making much more progress than today, especially because of the intense interactions between the theory and the experiment. It was the case despite the fact that these heroes of ours were much more ignorant about quantum gravity than we are today.

Friday

John Huth, the chair of our physics department, applied some of his numerous skills and he started the whole conference. I think that it would have been more difficult for Arthur to organize everything without John's support.

Two dinners were a part of the happening, but let me also say something about the talks. On Friday, David Gross '04 started. (On the picture on the right side taken in 2004, David Gross was showing the new wing of the Kavli Institute for Theoretical Physics which has already been completed.) His talk The Future of Physics, whose original edition was presented at the KITP Santa Barbara in October 2004, was very broad and entertaining. David Gross '04 was introduced by Norman Ramsey '89.

• David explained how trivial it was to squeeze the October conference, the 25th anniversary of the Institute, and the QCD Nobel prize into the same week. He also illuminated the method how the Laffer curve, popular during Reagan's administration (and used to argue that the optimal tax rate is much much smaller than 100 percent), may be applied to figure out the ideal length of a talk. Then he discussed 25 most important questions in various fields of physics - among them we find cosmology, general relativity, quantum mechanics including its interpretation, particle physics, string theory, condensed matter physics, biophysics, sociology of physics, and importance of physics and the KITP in the future (the answer to the last question was Yes, of course). Sorry if I forgot something. I remember most of the talk because it was the second time I heard it ;-), but I can't tell you everything.
• David argued, for example, that some people are afraid that quantum mechanics may fail at very short distances; it may fail for cats (or other complex systems); it may fail for conscious beings - as Roger Penrose would suggest. David Gross '04 said that the last proposal is even "sillier" than the cats. Murray Gell-Mann '69 who was sitting nearby vehemently agreed. David Gross '04 also explained why you can't kill string theory - even though some people in the audience would like to - because of, for example, the equivalence between gauge theories and string theory (such as AdS/CFT).

David Gross '04 was followed by his QCD friend Frank Wilczek '04, introduced by Lisa Randall. Frank talked about Asymptotic Freedom: from Paradox to Paradigm.

• Frank sketched interesting apparent paradoxes that people used to see in Nature. Paradoxes are very useful for physics, Frank argued, because the actual Universe is never paradoxical, and our attempts to resolve the paradoxes always leads to improved knowledge. An example of his paradox was that quarks are born free, but every time someone sees them, they're confined. And he explained how quantum field theory and QCD transmuted these paradoxes into new paradigms that make sense. Wilczek has also shown a graph that the masses of the hadrons may be calculated, even without the AdS/CFT dual of QCD that David Gross was calling for. Frank Wilczek also joked that he was expecting the 1 million dollar award from the Clay Institute for his proof, based on his transparencies, that QCD had a gap.
After a break, president Summers appeared in the hall B of the Science center. He gave a very good speech; it's not just my opinion, but also the opinion of Nima Arkani-Hamed, Frank Wilczek, David Gross, and others. Among other things, Summers said:
• During the last two months, I've learned a lot of physics lessons - such as turbulence, chaos, and strange interactions (LM: these are probably strong interactions involving the strange quarks). So far no Big Bang. Conferences like this one, with this huge concentration of talent and brains, are what the universities were created for and what will be remembered 400 years into the future. All small wars will be forgotten. The new laws and new drugs may be invented outside the universities, but sciences like physics have an eternal value.
Greg Moore then introduced Paul Steinhardt who talked about Cosmology in a False Vacuum.
• Paul's talk was constructed in such a way that everything seemed to follow from Sidney's insights about the false vacuum. The most exciting talk in Steinhardt's life was a seminar by Alan Guth about inflation. Paul Steinhardt reviewed some basic stuff about the vacuum decay and inflation, and then he discussed his cyclic Universes. He made a pretty good job: a scalar field can roll to a negative vacuum energy, the kinetic energy starts to dominate, and "w" from the equation of state becomes much greater than one. Steinhardt argued that "w much greater than one" has very similar properties to the cosmological constant with "w = -1". This suggests that the future will look much like the past, and it makes it natural to think about the cyclic Universe - which he also presented with an animation of two branes bouncing off each other many times.

Leon Cooper '72 then introduced Murray Gell-Mann '69 - the gentleman on the right from Thomas Appelquist. Murray was Sidney's adviser and he offered many interesting stories that have a relation to Sidney Coleman in his talk titled Recollections of Sidney. I will mention some of my private discussions with Murray below, so let me mostly skip this interesting talk.

• Just one or two comments. Murray also talked about the representation theory for the hadrons. Sidney played a rather important role in these developments, too. Murray mentioned that they sometimes incorporated the same particles into different representations - one of them was wrong and I forgot who was it. During his talk, Murray's cell phone started to ring twice. Murray Gell-Mann '69 interrupted his talk and studied who was calling him. "One call missed," was the answer after one minute of research. Gell-Mann, who is a Yale graduate, admitted that Harvard had been pretty good. Also, Harvard had created a string theory group only 25 years after Gell-Mann and his friends did the same thing at Caltech, which is not bad.
Howard Georgi then introduced Sheldon Glashow '79 who spoke about Small Matrices, Sidney, and Me. On the picture below, you can also see Kenneth Lane in the middle and Robert Schrader on the left (c.f. Osterwalder-Schrader methods to switch between the Euclidean and relativistic field theory).

• Shelly mentioned very amusing stories from their visit of the Soviet Union (Dubna). The bed broke under Glashow, and it was Sidney's happiest moment during the trip to Russia. At the airport, they were hungry and were able to penetrate from the Russian to the Polish side of the terminal. Finally they were lucky and the airplane departed. Sheldon Glashow '79 explained that after several years of collaboration, they became interested in slightly different questions in physics: Shelly was focusing on phenomenology while Sidney was more interested in the foundational issues. Nevertheless, Shelly also promoted some recent papers he wrote with Sidney in the late 1990s that dealt with tests of Lorentz violations. Shelly had another good point: he recalled David Gross's theory (the Laffer curve) about the length of the talk, and pointed out that David Gross was the only speaker who ran out of time. It was because David Gross has neglected special relativity: other observers always seem to think that your speech is slower than what you think.
Before the dinner, I spoke to several great physicists, for example Murray Gell-Mann '69. I asked him about Murray's commercial for Enron - "keep asking why" - and he described how he actually liked the content of the advertisement (the question "why" and "why not" is the most critical question there is), and how he met everyone from the company except for the CEO. Murray Gell-Mann '69 also confirmed that Feynman considered brushing the teeth to be a superstition, despite his rotty teeth. He clarified that it was not difficult to hire John Schwarz because Feynman did not attend the faculty meetings where these decisions were made. ;-)

The dinner was fancy, we drank some wine and ate several courses. We also listened to a concert of a staunch string theory advocate, namely Ursula Holliger who is an excellent harpist - Claude Debussy was the primary composer and I liked the fruits of his work a lot. Many people offered their testimonies about Sidney Coleman. For example, Frank Wilczek's wife, who also has a blog, said that Frank had spent the honeymoon with Sidney Coleman rather than her, spiritually speaking. One day after the wedding, Frank left Betsy to meet Sidney. Others described Sidney's excellent skills in mountaineering (he always knew where he was); in inventing simple arguments (for example, why the apparently larger size of the Moon near the horizon can't be a consequence of a lensing effect - consider how a chain of mechanically connected Moons filling the whole orbit would look like to see that no zooming of the angle is possible).

The stories included Sidney's smoking, teaching, his relation to religion, and so forth. Sidney was present at the dinner and thanked the participants for their participation. Several letters have been read. For example, David Politzer '04 did not attend because during the last year, he has already been travelling more than he would like. David Politzer '04 also thanked Sidney Coleman, his adviser, for his contributions to David Politzer's Nobel-prize-winning papers.

Saturday

On Saturday morning, there were two talks by Weinberg without PowerPoint, as Steven Weinberg '79 pointed out. The first talk - Vacuum Tunneling in de Sitter space - QFT in the Past and in the Future - was by Erick Weinberg (on the picture below, taken in my office, with Ki-Myeong Lee; guess who is who). Alan Guth from the M.I.T., the father of inflation (see the picture above; Alan G. should not be confused with another Alan G. who is an expert in inflation) introduced Erick Weinberg.

• Erick Weinberg who is currently the boss of the physics department at Columbia University was one of Sidney's students. He explained quantum tunneling in quantum mechanics, its special properties in quantum field theories, SO(4) invariant bounce instantons in the Euclidean spacetime, and novelties that arise when one tries to find and interpret similar solutions in the gravitational context (GR). One of the important questions was whether one should interpret a qualitatively symmetric instanton as a bubble of de Sitter vacuum A inside de Sitter vacuum B or vice versa.

The second talk on Saturday was a talk called Cosmological Correlations by Steven Weinberg '79 who was introduced by Kenneth Wilson '82.
• Steven quoted Sidney as saying that he could only see farther than others because he was standing in between the shoulders of dwarves. (This is actually what Isaac Newton originally wanted to say, but he decided to make the joke about Hooke more subtle.) Weinberg focused on Maldacena's calculation of the three-point functions (non-gaussianities). He attempted to calculate "one-loop corrections" to Maldacena's "classical" calculation. Weinberg also said that "Maldacena calls this observable 'zeta', but he is wrong because it should be called script R". The divergent integrals forced Weinberg to consider general relativity as a "renormalizable theory with an infinite number of counterterms"; moreover, these are counterterms in a time-dependent context which makes things more difficult. Cumrun Vafa, who was sitting on my right, was feeling uncomfortable about Weinberg's attempts to regularize quantized general relativity, and so was I, in a sense.
• Weinberg believes that current cosmology is at least comparably exciting as particle physics during "their" era.
The first talk on Saturday afternoon was by Gerardus 't Hooft '99. Before the talk, I had roughly 20 seconds to chat with Peter Woit. 't Hooft was introduced by Nati Seiberg.
• Gerardus spent a couple of minutes explaining how his name should be pronounced and spelled. The form of the name "Gerardus" is inspired by Latin, and it is only used in the passport, the Nobel prize documents, and at Luboš Motl's reference frame. Then he reviewed some of the history of gauge theory and its renormalizability (and the belief of the experts at that time that QFT was probably not the right description) and the speedy process in which Gerard's results were accepted. Also, in 1971, he found out that the beta function of QCD was negative and what it was. It was too a simple insight for him, so he did not publish it and this stuff was rediscovered in 1973 by David Politzer '04 and independently discovered and extended by David Gross '04 and Frank Wilczek '04. 't Hooft's heuristic explanation of -11 from the beta function arises as the sum of -12 from magnetic screening (magnets tend to direct themselves in the same direction as the original magnets, and the magnetic moment is important for the gluons) and +1 from the electric screening. Moreover, Gerard 't Hooft '99 speculated that the number 11 from the beta function may have a relation to string/M-theory. A discussion at the dinner revealed that 't Hooft's numerology is really the same one that we observed with Josh Grey in Santa Cruz: a pure non-supersymmetric gauge theory coupled to adjoint scalars has a vanishing 1-loop beta-function for 22 real scalars, which corresponds to a (non-existent) background "AdS_5 x S^21", which seems to have the same spacetime dimension as bosonic string theory.

• Gerard 't Hooft '99 then explained that his advisor Martinus Veltman '99 was kind of discouraging him from publishing various results. Also, at a conference in the 1970s, Veltman introduced 't Hooft to "two American gangsters", as Veltman called them. They identified themselves as Mr. Glashow and Mr. Coleman. Eventually, 't Hooft learned that Veltman would use the word "gangster" for anyone who was smarter than Veltman himself. 't Hooft also realized that Coleman and Glashow needed a few minutes to understand something that Veltman only understood after several hours. Well, I guess that 't Hooft's former advisor is not terribly happy if he reads this report, but it does not mean that 't Hooft's description is unfair. ;-)
• At any rate, 't Hooft then showed that the Standard Model had been completed, everything agreed at higher energies better than everyone expected. And therefore, the next natural step was to study quantum gravity. One of the ideas that 't Hooft presented in his talk - originally published 10 years ago or so - was that the elementary process in which a black hole is formed and evaporates can be visualized as an inflow of "blue" closed strings that sit on the "red" horizon; then they spread and fill almost the whole area of the horizon except for a few "red" holes; finally, the "red" closed strings escape from the horizon, becoming the Hawking radiation. 't Hooft argued that this is mathematically equivalent to a string process with an imaginary value of the string coupling constant. (At the dinner, 't Hooft argued that his theory living on the worldsheet was not quite a conformal field theory, but it was less clear what it was.) These interesting comments provoked Edward Witten to ask two questions - one of them about the generalization of the mechanism to higher-dimensional black holes.'t Hooft said that the worldsheet would have to become a higher-dimensional worldvolume (that's problematic because the higher-dimensional field theories are not expected to be well-defined in the UV).
• Note that 't Hooft contributions to string theory are important - the large N expansion of gauge theories and a string theory; holography (with Lenny Susskind). And 't Hooft has also educated several very good Dutch string theorists - Dijkgraaf, Verlinde, Verlinde. He has also taught string theory in Utrecht.

Prof. 't Hooft's statement

After seeing this report, Gerard 't Hooft asked me to add this statement:

• "Oeps, in my comparison of Sidney's fast and brilliant mind with that of my advisor Veltman, I must have left a false impression of my admiration of Veltman. I was making jokes about him (much as how he would do that himself), but please be assured that he is brilliant in his own way, as his richly deserved Nobel Prize testifies."
The last talk was Emergent Phenomena in Condensed Matter and Particle Physics by Edward Witten. Arthur Jaffe introduced the speaker to a crowded audience in Jefferson 250 - he did not have to. The room was really full. For example, my concentration was reduced because I was surrounded by several beautiful girls. ;-)
• Witten started with rudimentary comments about the mathematical analogies between particle physics and (critical phenomena in) condensed matter physics and statistical physics. He explained that a weak coupling implies that the observed phenomena are not really emergent; they rather reflect the underlying degrees of freedom directly. However, there is a lot of non-trivial new physics that occurs as a simplified description of a large number of elementary building blocks.
• Witten then focused on gravity. He explained that there are no local gauge-invariant degrees of freedom in gravity. Consequently, gravity can't be an emergent phenomenon arising from conventional (non-gravitational) degrees of freedom defined in the same spacetime. For example, all "consensed matter" attempts to describe gravitons as spin 2 bound states of some "conventional" objects living in the ultimate spacetime are doomed because the "conventional" theories contain local gauge-invariant operators that can't exist in a theory of gravity because of general covariance. This is mathematically shown to be the case in the Weinberg-Witten theorem from 1980 - in whose derivation Sidney Coleman was helpful, as Witten mentioned.
• Witten continued by saying that while gravity can't be an emergent phenomenon in the same ultimate spacetime, it might be emergent as long as the whole spacetime is emergent. Mirror symmetry, topology change, T-dualities are examples of hints that spacetime is emergent, and Maldacena's duality is a particular case in which we can see how spacetime - at least one dimension of it - emerges.
Witten has probably received more questions than the other speakers combined. Weinberg asked whether Witten meant "supergravity" or whether one can holographically describe non-supersymmetric gravitational theories. Cumrun Vafa, who was sitting in the audience, mentioned that one can consider non-supersymmetric orbifold, but Witten encouraged everyone to be careful because these non-supersymmetric compactifications may be unstable. Shiraz Minwalla asked whether Witten agreed that we had no known examples in which time, as opposed to space, seemed to be emergent. I did not have a feeling that Edward Witten was answering exactly this question but he still managed to say something interesting. Note that relativity implies that anything that holds for space should hold for time, too - and therefore our apparent inability to show that time is emergent may lead to us to an incorrect conclusion.

External sources about Sidneyfest

There was another dinner on Saturday in the Eliot House - and interesting discussions with many people including Stephen Wolfram, Frank Wilczek and his wife, Gerard 't Hooft, Shiraz Minwalla, and others. The event is also mentioned on blogs of

Also, Errol Morris, the world's most famous document maker, has been filming interviews in the physics library with many of the physicists mentioned in this article.

The picture above makes it pretty clear that I thought that the whole bulk of Sheldon Glashow would appear on the photograph, and I was wrong. Also, by this point, most readers have probably understood that the numerals following most of the surnames indicate the year of their Nobel prize.

#### snail feedback (42) :

reader Anonymous said...

Sounded like a great time Lubos. Will there be any photos of the event available to see, or were videos of the talks made?
Best
Steve

reader Anonymous said...

Oops...never noticed your last sentance there where you mention you will add the photos:) Look forward to them then.
steve

reader Anonymous said...

He explained that there are no local gauge-invariant degrees of freedom in gravity. Consequently, gravity can't be an emergent phenomenon arising from conventional (non-gravitational) degrees of freedom defined in the same spacetime.

It doesn't follow. Especially since we don't have evidence that spacetime is truely diffeomorphism covariant.

reader Anonymous said...

See, if general relativity is really an emergent theory, then like all emergent symmetries, operators which aren't invariant under the symmetry in question can still be observables in principle. It's just increasingly hard to do so at large scales.

reader Anonymous said...

He explained that a weak coupling implies that the observed phenomena are not really emergent; they rather reflect the underlying degrees of freedom directly.

Huh? Phonons are weakly interacting. So are some other quasiparticles.

And honestly, what's up with all this bashing of emergent phenomena lately? I mean, even your beloved AdS/CFT correspondence predicts that fields residing on the IR brane are emergent fields in the dual quasiCFT theory. Even if they happen to be weakly coupled...

reader Anonymous said...

Hi Lubos, FYI that's Thomas Appelquist next to Murray Gell-Mann. Regards, Ohne

reader Anonymous said...

Thanks for an excellent post Lubos; you really captured the excitement and a sense of celebration that I would imagine such an important, albeit informal, event might have. And your jokes were funny, too;-). If you could give us a 'heads up' when videos etc. become available that would be great.

Nice one

Robert

reader Anonymous said...

When the Witten-Weinberg paper predicts that there can be no massless charged spin-1 particles under certain assumptions and we know there are nonAbelian Yang-Mills theories in the Coulomb phase, you know that some of their assumptions don't hold in general. In fact, as they themselves have pointed out, the Yang-Mills fields themselves carry charges, but here's the catch, the Yang-Mills charge can't be written as the integral over a local current field which is both gauge covariant and Lorentz covariant because gauge transformations do not commute with spatial rotations. The total charge of all the nonYang-Mill fields is not gauge covariant. Neither is the total charge of all the Yang-Mills fields. We'd have to sum both (and insist upon boundary conditions which basically state that the Yang-Mills and charge fields tend towards zero at spatial infinity). See, it's the assumption that the total charge is local in the sense that it can be written as the integral of a local field over a spacelike slice which fails for gauge theories. Of course, we can always define a pseudocurrent field which is either nonPoincare covariant or nongauge covariant, but that's just an unphysical trick. The truth of the matter is, charges are nonlocal, i.e. extended in nonAbelian gauge theories.

Now let's go on to general relativity. Once again, we can't simply write down the energy-momentum as the integral of a stress-energy tensor in a local sense. Not unless we introduce an unphysical pseudostress-energy tensor and insist that spacetime is asymptotically flat. Same problem here. But why should we assume that charges and energy-momentum are local?

This brings to mind the attempts to regularize Weyl fermions on a lattice. We encounter fermion doubling problems unless we introduce a nonlocal action.

reader Lumo said...

Dear Anonymous,

the first statement of Weinberg-Witten is that massless particles with spin greater then one can't exist in conventional Lorentz-invariant theories. (This excludes, for example, the possibility to explain the massless graviton - a source of the long-range gravity force - as a composite of some other particles in non-gravitational Lorentz invariant theory - something that the condensed matter emerging gravitational physicists don't know or don't appreciate.)

It seems that you refer to the second statement that there can't exist massless particles with a conserved charge and spin above 1/2. (Note that the word "massless" was forgotten in this part of the abstract, but it is inside the article.)

I would believe that you might guess that Witten and Weinberg, two leaders of particle physics, knew the basic phases of gauge theories in 1980. ;-) The Coulomb phase you mentioned is definitely not a counterexample. The photon does not carry any conserved charge, and the W and Z bosons are not massless.

If you want to find loopholes in their theorem, I think that you will have to make a harder job than you did, by several orders of magnitude. ;-)

Best
Lubos

reader Anonymous said...

Oh, another thing, theories with massless particles suffer from infrared complications, like brehmstrahlung. So, working with quantities like

< p'|J|p > and < p'|θ|p > is a bit questionable.

The usual way to regularize the IR divergences is the give the massless particles a tiny mass and take the limit as that goes to zero. But in that case, their whole proof falls flat.

reader Anonymous said...

Lubos, if you add enough flavors of charged fermions to a Yang-Mills theories, we will see massless charged spin-1 bosons.

You know full well I wasn't thinking of the Standard Model.

reader Lumo said...

Nope. The quantities you mentioned don't have and can't have infrared divergences in them. These are exact matrix elements of meaningful (global) observables between real states.

What can have infrared divergences are the scattering amplitudes, if you forget to calculate the inclusive cross section that includes the production of soft photons below some threshold. But that's a very different quantity than what you wrote.

In physics, you can't just say "there may be some problem with something, and therefore I don't want to believe a theorem". An argument in physics must actually and carefully figure out whether the problem with a particular thing exists or not. The problem you tried to mention does not exist.

reader Lumo said...

No, you can't get massless spin 1 bosons in Yang-Mills theory that carry a nonzero conserved charge, regardless of the number of flavors you introduce. This would violate the Weinberg-Witten theorem. Be sure that you're doing something wrong.

reader Anonymous said...

Geez, Lubos!

J(0)|p> contains |p'> mixed together with the same massless particle with an arbitrary number of low energy particles. And without a mass gap, we can't disentangle them easily. Because of that, we need to regularize <p'|J(0)|p >.

And go read the paper yourself! There is a pseudocurrent field for nonAbelian theories in the Coulomb phase which isn't Lorentz covariant and there is another which is Lorentz covariant but includes the Gupta-Bleuler or some sort of BRST cohomological trick which messes up the helicity structure.

reader Lumo said...

"Because of that, we need to regularize [p'|J(0)|p]."

Regularize whatever you want if you compute the quantity in some initially divergent way, but the important fact is that this quantity is meaningful for any two actual states in the Hilbert space.

It's also not true that J(0) acting on a physical state of a massless particle (a full single-particle state) creates an infinite number of soft quanta. The evolution operator or the S-matrix does such a thing, but the current does not.

Your attempts to confuse everything are not terribly important or useful. The Weinberg-Witten theorem is more important by several orders of magnitude; it is science where sharp statements are obtained, in sharp contrast with your confused fog.

reader Anonymous said...

the first statement of Weinberg-Witten is that massless particles with spin greater then one can't exist in conventional Lorentz-invariant theories

No, Lubos, no! The first theorem deals with theories where the energy-momentum is the integral of a Lorentz-covariant stress-energy tensor, i.e. where the energy-momentum is local.

The problem with pseudostress-energy tensors in asymptotically flat spacetimes is that a local charge in the coordinate system will shift the distribution of the energy-momentum. Since local coordinate transformations, i.e. those which doesn't change at spatial asymptotic infinity are completely unphysical, this means energy-momentum isn't localized at all. The same comments applies to nonAbelian Yang-Mills theories in the Coulomb phase.

And < p'|J(0)|p> and < p'|θ(0) |p > does describe a scattering. One where an external interaction is applied at the spacetime origin.

reader Anonymous said...
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reader Lumo said...

"And [p'|J(0)|p] and [p'|θ(0) |p] does describe a scattering."

You know that what you write is not true. |p] is a one-particle state, and there is nothing to scatter with. There are no infrared divergences in this amplitude. Just try to calculate it. J and theta are simple polynomials in the elementary fields, and there is no place where IR divergences could creep in.

"No, Lubos, no! The first theorem deals with theories where the energy-momentum is the integral of a Lorentz-covariant stress-energy tensor, i.e. where the energy-momentum is local."

That's right. I just don't know why you write "No, Lubos, no". This is what the words "conventional theories" mean.

"Since local coordinate transformations, i.e. those which doesn't change at spatial asymptotic infinity are completely unphysical, this means energy-momentum isn't localized at all."

That's also right. This is one of the basic ideas behind the theorem. Gravity would need a delocalized stress-energy tensor, much like other fields, while the conventional theories always give localized objects, which contradicts diff invariance. WW make an argument that works for other spins, too.

reader Lumo said...

OK, it has been enough, dear reader. This article is about Sidneyfest - it is not dedicated to foggy pseudoarguments trying to find an un-identified (and un-identifiable) problem with the Weinberg-Witten theorem.

You're wasting our time. If you focused on the actual science and tried to look at all the relevant statements sharply and (self-)critically, you could avoid writing all this nonsense you keep on writing.

reader Anonymous said...
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reader Anonymous said...
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reader Anonymous said...
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reader Lumo said...

I've erased several more comments of a crackpot who questioned not only the WW theorem but also the existence of one-particle states etc., and I strongly discourage the crackpot to write new comments of this kind. Thank you very much.

reader Anonymous said...
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reader Anonymous said...
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reader Anonymous said...
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reader Anonymous said...
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reader Lumo said...

That rather obnoxious crackpot keeps on filling this forum by silly remarks about the non-existence of particles, various misconceptions that originated from the so-called algebraic quantum field theory, "infraparticle problem", and related myths.

I ask her or him to stop filling my blog - especially this article about the conference celebrating Sidney Coleman - with this rubbish. If someone considers these things and arguments "physics", it's her problem, but I consider them results of sloppy thinking and worthless pieces of confusion. This includes various papers by Schroer, Buchholz, and others.

I encourage the person who writes these controversial remarks, to say it politely, to establish her own blog dedicated to the people with the same perverse interests. I am also sure that there exist hundreds of places on the internet for crackpots to exchange their ideas about various alleged inconsistencies of QFT, but this blog is not meant to be one of them.

There is a striking excess of supply of crackpots (not only) on this blog, and their market value is definitely negative.

There are literally hundreds of silly papers based on obvious misunderstanding of the very basics of quantum field theory - most of the papers in the last 30 years that use the "fancy" term "algebraic quantum field theory", for example, and we would be doing nothing else whatsoever if we had to explain why each of these wrong papers is wrong.

In any theory in the Minkowski space that has at least qualitative ability to resemble the real world, the single-particle states are well-defined, and their properties may be used to derive the results of Weinberg and Witten as well as many other results. Weinberg and Witten have ruled out, among other things, emergent gravity built from more elementary constituents in relativistic QFT. The "infraparticle problem" claiming that one can't separate single-particle states from soft photons is silliness.

There are infrared problems in the presence of massless particles, but they always indicate that we have asked an incorrect question. Neither of these things implies a physical inconsistency - and the non-existence of single-particle states that are energy-momentum eigenstates would be an inconsistency.

A single-electron state, for example, is well-defined in the full theory - both string theory as well as the Standard Model. It's true that it is a different state than the state created by the bare Dirac field operator, but it is nevertheless a well-defined state in the physical Hilbert space.

Even if someone does not follow the technology, I assure her that if Weinberg and Witten thought that the "infraparticle problem" were a real important issue to keep in mind when talking about massless single-particle states, they would have taken this result into account and cited it.

reader Mark said...

What a shame you've had to deal with so many crackpot comments...I thought it was a first-class post, with great photos, and I recommended it to my readers, though none of us, I'm sure, are specialists. Thanks for sharing, that looks like it was quite the event.

reader Quantoken said...
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reader Quantoken said...
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reader Plato said...

Witten then focused on gravity. He explained that there are no local gauge-invariant degrees of freedom in gravity. Consequently, gravity can't be an emergent phenomenon arising from conventional (non-gravitational) degrees of freedom defined in the same spacetime. For example, all "consensed matter" attempts to describe gravitons as spin 2 bound states of some "conventional" objects living in the ultimate spacetime are doomed because the "conventional" theories contain local gauge-invariant operators that can't exist in a theory of gravity because of general covariance.------

I am glad you have changed your anonymous settings.

I constructed a post today, becuase I am trying to pierce what is, and maybe easily accessible to minds like those who visit here.

I have no pre agenda and nothing to sell, but what my heart and determination show to undertanding this world you fellows deal with.

So to this end, in the spirit of the paradoxic, what had theoretics hoped to accomplish?

Power of Symmetry Allows Us to Unify Disparate Pieces?

Maybe I am a bit niave in this regard, but seeing such minds as shown in this gathering of Sidneyfest," reminds me of what must have felt good to Einstein, in his early years of the "Olympian Academy."

In later years, the Solvay meetings were perspectively drawing attention to thought experiments and did reveal the positions of others in their comments about one another.

But the truth of later years, in regards to Einstein dismisses what some of us might think as wasted years, to realize a wondeful solution manifested in the spirit of inquiry.

reader CapitalistImperialistPig said...

Great post Lubos! I really enjoyed all the stories from and about the physics greats of our time.

reader Plato said...

Hooft recognized the troubles with trying to model a quantum mechanical view from current model depictions?

Of a system that would be vast in probabilistic determinations. This is what is laying out there in consideration when you think that a method could be devised in Quantum computation?

Smolin and others, work at it from one perspective, while in the area of Blackhole considerations, it would have had to be much more specific?

If massless representations are developed from this blackhole in terms of Hawking radiation, then lying beneath the framework, there had to exist some method(higher dimensional analysis), that would automatically reveal the nature of the graviton, as it is describing for us, those gravitational waves in space plus time? This probabilistic determination lies outside of a four dimensional view?

How would such features be developed at the basis of quantum computation? To have this vast resource, automatically deciphering ligo analysis, instead of using Seti framework for consideration?

I am not sure either. I am still learning here.

reader Plato said...

Paul's talk was constructed in such a way that everything seemed to follow from Sidney's insights about the false vacuum. The most exciting talk in Steinhardt's life was a seminar by Alan Guth about inflation. Paul Steinhardt reviewed some basic stuff about the vacuum decay and inflation, and then he discussed his cyclic Universes. He made a pretty good job: a scalar field can roll to a negative vacuum energy, the kinetic energy starts to dominate, and "w" from the equation of state becomes much greater than one. Steinhardt argued that "w much greater than one" has very similar properties to the cosmological constant with "w = -1". This suggests that the future will look much like the past, and it makes it natural to think about the cyclic Universe - which he also presented with an animation of two branes bouncing off each other many times.

Again here if one did not understand the nature of the vacuum, it would have been less likely that the bounce might have been understood.

What is the true vacuum in these cases? How would you express this in a universe that could move in such a way to speak to the friedmann equations like it does?

So early on here, I with others, looked at the Casimere plates for analogy here in consideration.

Whether it's right or not, it was the action inbetween the plates that coordinated some thinking here.

reader Fyodor Uckoff said...

Why is the blog so quiet?

reader betsythedevine said...

Hi Lubos--I'm glad you wrote up the SidneyFest, and you did a lovely job. My vanity makes me want to add that Frank Wilczek spent our honeymoon with Sidney Coleman because Frank left for Sicily (Erice summer school) the very day after we got married. We had zero money, so I stayed behind in Princeton. I blogged here about how great email would have been: http://betsydevine.weblogger.com/2004/02/07

reader Jack Sarfatti said...

Emergent Gravity from Vacuum ODLRO
by Jack Sarfatti

The Theory of Everything for Everyone

The negative energy virtual electron Dirac Sea is unstable and forms the Higgs Ocean with the Vacuum ODLRO PSI. For simplicity assume a toy model with G/H = S1.

The Einstein-Cartan Tetrad 1-form is

e = I + B

I = identity

Higgs Ocean Spontaneous Symmetry Breaking in the inflation phase transition

B = (Lp/2pi)"dArgPSI"

B is also the the local gauge potential from local gauging of T4 to Diff(4).

B is closed but not exact.

Integrals of B on non-bounding cycles are NLp with integer winding number N.

Flux without flux is

NLp = A(dB)

F = (dB) =/= 0

dF = 0

d*F = *J

even though dB = 0

For a vortex in ordinary space on z axis where |PSI| = 0, in cylindrical coord

(dB) = NLp/4pir^2

Einstein's emergent curved space time is from the EEP

g(curved) = (I + B)(Minkowski)(I + B)

Under a Diff (4) GCT

g' = X(I + B)(Minkowski)X(I + B)

Quantized Goldstone vibrations in argPSI are not spin 2 gravitons.

No gravitons ever. No quantum foam.

That's All Folks!

reader Debbie said...

Sid was a much beloved friendly acquaintance, whom I have not seen for several years, and sadly missed. I was glad to find this, almost three years later and after hearing of his death.

Thank you.

reader R.DILEEP said...

Hi there!

I am R.DILEEP , from Kerala,India.
(At present I hold an M.Sc. in Physics...hope soon to become a real Theoretical Physicist!)
This blog really attracted me...simply because it nourished and polished my thinking about physics and physicists...the author of this blog has done a crucial step in making the informal atmosphere accessible to anyone with a serious quest to understand physics and physicist's views!

Really an outstanding blog!

Through this site..."I wish the very best of Health and Happiness to Professor Sidney Coleman and of course to this blog's Physicist author"!

Best,
R.DILEEP.
hTTP://dileepphysicist.blogspot.com

reader Martín said...

Hi Lubos,

do you know if the interviews recorded by Errol Morris are available on the web?

Thanks.

reader sedrik said...

Bravooo!