Strings 2010: Schedule of Talks

[marcus]

More titles were posted today, so I'll update:

Davide Gaiotto (IAS Princeton)
Towards a classification of four dimensional N=2 gauge theories

Edward Witten (IAS Princeton)
From Gauge Theory To Integrability And Liouville Theory

Gregory W. Moore (Rutgers U.)
Say ''Halo!'' to new walls and new indices

Fernando Quevedo (Cambridge U. & CERN)
Phenomenological Implications of Toric Singularities

Xi Yin (Harvard, U.)
High Spin Gauge Theory and Holography

Savdeep Sethi (Chicago U. EFI)
Fluxes, Geometries and Non-Geometries

Nima Arkani-Hamed (IAS Princeton)
Scattering Amplitudes and the Grassmannian

Steven Weinberg (U. of Texas, Austin)
Gravity at High Energyhttp://mitchell.physics.tamu.edu/Conference/string2010/TitleofTalks.html
+++++++++++++++++++++++++++

Weinberg's talk is almost certainly 4D and about the running of gravity at high energy. His asymptotic safety explanation of (1) inflation without an exotic "inflaton" field and (2) a graceful exit from inflation as the energy scale eases down from early universe conditions.
The title "Gravity at High Energy" strongly hints that he will present stuff from his two recent papers on this. I've blued talks that are likely to be 4D or non-stringy for some other reason.

for (4D gauge theory) background on Witten's talk:
http://arxiv.org/abs/1002.0888 (Nekrasov and Witten)
"...Omega-deformation of four-dimensional gauge theory ... linking the Omega-deformation to integrable Hamiltonian systems in one direction and Liouville theory of two-dimensional conformal field theory in another direction."
http://arxiv.org/abs/1001.2933 (Witten)
"..analytic continuation of three-dimensional Chern-Simons gauge theory... analytic continuation of three-dimensional quantum gravity ... twisted version of N=4 super Yang-Mills theory in four dimensions."
http://arxiv.org/abs/0908.4052 (Nekrasov et al)
"Quantization of Integrable Systems and Four Dimensional Gauge Theories"

The Princeton contingent is leaning 4D these days. Gaiotto and Witten, and let's not forget:
Yuji Tachikawa (IAS Princeton)
2d CFTs from 4d N=2 gauge theories

Two other papers of note:
Nikita Nekrasov (IHES)
The uses of Omega-backgrounds
Andrew Strominger (Harvard U.)
The Kerr-Fermi Sea (already checked, a 4D paper)

About Arkani-Hamed's talk, his last three papers are about N=4 SYM (N=4 super Yang Mills). Which, although plenty of connections with e.g. twistor string theory are pointed out, is primarily a 4D QFT, or?
Anybody want to correct me on this? I see this page on N=4 SYM says 4D:
http://www.physics.thetangentbundle.net/wiki/Quantum_field_theory/N%3D4_super_Yang-Mills_theory
How to classify?

 

[Physics Monkey]

Not rain on anyone excited about the return to 4d, but I don't think this means string people are tired of extra dimensions. Here are some examples of what I mean:

The people talking about 4d \mathcal{N} = 2 gauge theory are mostly talking about highly artificial math theories that have nothing or almost nothing to do with our world. Moreover, these theories draw their power from extra dimensions anyways, for example, there are constructions in M theory of these things. Additionally, the 4d 2d connection that tachikawa is talking about can be understood as various different kinds of compactification in 6 dimensions. I think Nima is also talking about an incredibly artificial theory, the \mathcal{N} = 4 theory. This thing doesn't have much to do with the real world despite being 4 dimensional (except possibly at finite T as a model of the rhic plasma).

Xi Yin's talk is about doing holography on the O(N) vector model in 3d which seems to require a complete tower of massless higher spin fields in the bulk. The other talks about holography are also mostly what marcus calls applications of "string math". The possible exception is Eva Silverstein, when I heard her talk, she said the partial goal was to have a relatively realistic 4d theory of quantum gravity, albeit in AdS.

Washington Taylor is explicitly in 6d. The F-theory people are working on compactifications from 12d.

Overall I feel that the apperance is 4d is not really because of an interest in realistic physics, but more because that's where the math has been leading lately. So not to sound too cynical, but mostly I see the usual dominance of mathematical excitement plus holography. It just happens to have something to do with 4d this time!

 

[marcus]

...Overall I feel that the apperance is 4d is not really because of an interest in realistic physics, but more because that's where the math has been leading lately...

Thanks for sharing your perspective on this. It's really helpful. In fact you partly confirm what i had myself begun to gather from looking over the papers!
Just because a number of them are homing in on 4D (and lower dimensions like 6D) does not mean they are necessarily getting more real world.

I would agree with your characterization of some of the work as extremely artificial and mathematics-driven.

BTW what is your view about the Wednesday group?

Wednesday
1.Gary Horowitz (UC Santa Barbara)
Recent Developments in Holographic Superconductors
2. Jerome P. Gauntlett (Imperial College)
Holographic Superconductors in M-Theory
3. Joseph Polchinski (KITP, Santa Barbara)
Semi-holographic Fermi Liquids
4. Christopher P. Herzog (Princeton U.)
Holographic Superconductors with Pencil and Paper

This research gambit strikes me as NOT directed towards unification, or ToE, or a fundamental theory of nature. It looks like part of a broad retreat from those earlier central goals.
More like a specialized application of some math techniques (which happened to be developed in the string context). Again, however, one should probably not expect the "holographic superconductor" research to be actually real world applicable---it could be more of what you described as artificial and math-driven---or on the other hand it could turn out useful. I'd appreciate your take on it.

 

[marcus]

Putting the whole Strings 2010 program together, it looks to me tentatively as if about 12 or the 41 talks are not about string theory as generally understood. Quite a few look like exit strategies from extra dimensions.

Monday
1. Michael Dine (UC Santa Cruz)
Symmetries in String Theory
2. Davide Gaiotto (IAS Princeton)
Towards a classification of four dimensional N=2 gauge theories
3. Yuji Tachikawa (IAS Princeton)
2d CFTs from 4d N=2 gauge theories
4. Jaume Gomis (Perimeter Institute)
The Virtue of Defects in Gauge Theories and 2d CFTs
5. Nadav Drukker (Humboldt U., Berlin)
A supermatrix model for ABJM theory
6. Gregory W. Moore (Rutgers U.)
Say ''Halo!'' to new walls and new indices
7. Xi Yin (Harvard, U.)
High Spin Gauge Theory and Holography
8. Fernando Quevedo (Cambridge U. & CERN)
Phenomenological Implications of Toric Singularities
9. John Ellis (CERN)
Searching for new physics at the LHC

Tuesday
1. Hirosi Ooguri (CALTECH)
Instability with Chern-Simons Terms
2. Johannes Walcher (CERN)
Compact Open Topological String
3. Savdeep Sethi (Chicago U. EFI)
Fluxes, Geometries and Non-Geometries
4. Nikita Nekrasov (IHES)
The uses of Omega-backgrounds
5. Edward Witten (IAS Princeton)
From Gauge Theory To Integrability And Liouville Theory
6. Andrew Strominger (Harvard U.)
The Kerr-Fermi Sea
7.Jan de Boer (U. of Amsterdam)
(Non) geometric Aspects of Black Hole Microstates
8. Ashoke Sen (Harish-Chandra I. )
Black holes and discrete symmetry
9. Washington Taylor (MIT)
Global aspects of the 6D supergravity landscape
10. Mirjam Cvetic (U. of Pennsylvania)
Non-perturbative effects for Type II and F-theory vacua

Wednesday
1.Gary Horowitz (UC Santa Barbara)
Recent Developments in Holographic Superconductors
2. Jerome P. Gauntlett (Imperial College)
Holographic Superconductors in M-Theory
3. Joseph Polchinski (KITP, Santa Barbara)
Semi-holographic Fermi Liquids
4. Christopher P. Herzog (Princeton U.)
Holographic Superconductors with Pencil and Paper
5. Silverstein TBA
6. Ilarion V. Melnikov (AEI Potsdam)
Linear sigma models and heterotic moduli spaces

Thursday
1. Nima Arkani-Hamed (IAS Princeton)
Scattering Amplitudes and the Grassmannian
2. Jan Louis (Hamburg U.)
Spontaenous N=2 -> N=1 supersymmetry breaking
3. Dieter Lüst (Max Planck Institute & ASC Munich)
Supersymmetry breaking on generalized geometries
4. Sakura Schafer-Nameki (KITP, Santa Barbara)
F-theory GUTs in Three Steps
5. Natalia Saulina (Perimeter Institute)
Compact F-theory GUT's with PQ symmetry
6. Steven Weinberg (U. of Texas, Austin)
Gravity at High Energy
7. Petr Horava (UC & LBL Berkeley)
Quantum Gravity with Anisotropic Scaling
8. Lance J. Dixon (SLAC)
Perturbative Ultraviolet Behavior of N=8 Supergravity
9. Michael B. Green (Cambridge U.)
String Dualities and Ultraviolet Behaviour of Supergravity

Friday
1. Juan Maldacena (IAS Princeton)
Minimal surfaces in Anti-de-Sitter, Wilson loops and scattering amplitudes
2. Dario Martelli (King's College)
Interpolating geometries and gauge/gravity duality
3. Vladimir Kazakov (ENS and Paris U. VI-VII)
Y-system for the spectrum of planar AdS/CFT: news and checks
4. Shamit Kachru (KITP, Santa Barbara)
New Horizons in AdS/CFT
5. Liam McAllister (Cornell U.)
Nonperturbative Contributions to D3-brane Potentials
6. Igor Klebanov (Princeton U. )
Branes with Topological Charges and AdS/CFT
7. Leonard Susskind (Stanford U.)
Eternal Inflation and Holography

The schedule:
http://mitchell.physics.tamu.edu/Conference/string2010/Conference.html
The titles:
http://mitchell.physics.tamu.edu/Conference/string2010/TitleofTalks.html

+++++++++++++++++++++++++++

Weinberg's talk is almost certainly 4D and about the running of gravity at high energy. His asymptotic safety explanation of (1) inflation without an exotic "inflaton" field and (2) a graceful exit from inflation as the energy scale eases down from early universe conditions.
The title "Gravity at High Energy" strongly hints that he will present stuff from his two recent papers on this. I've blued talks that are likely to be 4D or near-4D, like 6D with no use of compactified dimensions.

for (4D gauge theory) background on Witten's talk:
http://arxiv.org/abs/1002.0888 (Nekrasov and Witten)
"...Omega-deformation of four-dimensional gauge theory ... linking the Omega-deformation to integrable Hamiltonian systems in one direction and Liouville theory of two-dimensional conformal field theory in another direction."
http://arxiv.org/abs/1001.2933 (Witten)
"..analytic continuation of three-dimensional Chern-Simons gauge theory... analytic continuation of three-dimensional quantum gravity ... twisted version of N=4 super Yang-Mills theory in four dimensions."
http://arxiv.org/abs/0908.4052 (Nekrasov et al)
"Quantization of Integrable Systems and Four Dimensional Gauge Theories"

The Princeton contingent is leaning 4D these days. Gaiotto and Witten, and let's not forget:
Yuji Tachikawa (IAS Princeton)
2d CFTs from 4d N=2 gauge theories

Two other papers of note:
Nikita Nekrasov (IHES)
The uses of Omega-backgrounds (appears based on a 4D paper)
Andrew Strominger (Harvard U.)
The Kerr-Fermi Sea (already checked, a 4D paper)

About Arkani-Hamed's talk, his last three papers are about N=4 SYM (N=4 super Yang Mills). Which, although plenty of connections with e.g. twistor string theory are pointed out, is primarily a 4D QFT, or?
Anybody want to correct me on this? I see this page on N=4 SYM says 4D:
http://www.physics.thetangentbundle.net/wiki/Quantum_field_theory/N%3D4_super_Yang-Mills_theory
How to classify?

I wasn't sure about the Holographic Superconductors talks on Wednesday. Tentatively colored a couple of them green to indicate doubtful connection with central string concerns such as unification and fundamental particle physics.

 

[Haelfix]

Of the authors listed, only Weinberg and Horava are working on decidedly non stringy material. The rest is basically business as usual.

Eyeballing the list, the biggest change from recent years is the large amount of interest in Ftheory (both the phenomenology and some of its ramifications) and the new holographic superconductor ideas (nearly a whole day devoted to that!).

Meanwhile there is less ABJM stuff than last year.

 

[MTd2]

Witten's talking about 4D is no surprising. His most important contributions, since the beginning of his career, were about 3D and 4D theories. He got a fields for that.

 

[marcus]

If anyone wants to check for trends here is the website for Strings 2005, for comparison.
Strings 2005 had some 415 registered participants. It was at the U. Toronto, in July
http://www.fields.utoronto.ca/programs/scientific/04-05/string-theory/strings2005/index.html
Strings 2010 has 192 participants. Maybe we can compare the titles of talks and get an idea if there is any shift. In 2005 there were 45 regular talks (plus the public lectures and the evening panel discussion concerning "The Next Superstring Revolution")

==quote 2005 talks==
Strings 2005 (July 11-16, 2005)

Panel Discussion: The Next Superstring Revolution
Robbert Dijkgraaf (Amsterdam), Strings05 Public Lecture:
Strings, Black Holes, and the End of Space and Time
Leonard Susskind (Stanford), Strings05 Public Lecture:
Cosmic Landscape: String Theory and the Illusion of Intelligent Design

Nima Arkani-Hamed, Harvard:
HEP circa 2010
Vijay Balasubramanian, Pennsylania:
The Library of Babel: Holography and Quantum Foam
Melanie Becker, Maryland:
M-theory Cosmology
Niklas Beisert, Princeton:
Applying Integrability in AdS and CFT
Iosif Bena, UCLA:
Geometric Transitions, Black Rings and Black Hole Microstates
Dick Bond, CITA, Toronto:
Measuring Cosmic Parameters
Freddy Cachazo, Perimeter Institute:
Recent Progress in Perturbative Gauge Theories
Atish Dabholkar, Tata Institute:
Going beyond Bekenstein and Hawking
Frederik Denef, Rutgers:
Constructions and distributions of string vacua
Albert de Roeck, CERN: (no audio available)
Physics beyond the Standard Model at the LHC
Bernard de Wit, Institute for Theoretical Physics & Spinoza Institute, Utrecht:
Supersymmetric Black Hole Partition Functions
Michael Dine, Santa Cruz Institute for Particle Physics:
Branches of the Landscape
Michael Douglas, I.H.E.S., Rutgers:
Is the number of string vacua finite?
Henriette Elvang, UC Santa Barbara:
Black rings
Sergey Frolov, Max-Planck-Institut fur Gravitationsphysik Albert-Einstein-Institut, Potsdam:
Multi-parameter deformations of AdS_5 x S^5 geometry
Amihay Hanany, MIT:
Brane Tilings, Dimers and Quiver Gauge Theories
Petr Horava, California, Berkeley & LBNL: (no audio available)
Noncritical M-Theory in 2+1 Dimensions as a Nonrelativistic Fermi Liquid
Gary Horowitz, UCSB:
A new endpoint for Hawking evaporation
Shamit Kachru, SLAC, Stanford:
A classical type IIA landscape
Renata Kallosh, Stanford:
String cosmology and the index of the Dirac operator
Anton Kapustin, Caltech:
Disorder operators in gauge theories and duality
Per Kraus, UCLA:
Attractors, Anomalies, and Black Hole Entropy
Martin Kruczenski, Brandeis:
Strings from N=1 superconformal gauge theories
Hong Liu, MIT:
Black hole singularities in Yang-Mills theories
Oleg Lunin, IAS:
Marginal deformations of field theories and their gravity duals
Juan Maldacena, IAS:
Free fermions and BPS geometries
Dario Martelli, CERN:
New results in AdS/CFT
Hirosi Ooguri, CalTech:
Topological String Theory
Joseph Polchinski, KITP, UCSB:
Update on cosmic strings
Fernando Quevedo, Cambridge:
Exponentially large extra dimensions and soft supersymmetry breaking in type IIB flux compactifications
Vyacheslav Rychkov, ITFA, Amsterdam:
Geometry quantization from supergravity
Nathan Seiberg, IAS:
New Phenomena in 2d String Theory
Ashoke Sen, Harish-Chandra Research Institute:
Extremal black holes in higher derivative gravity
Eva Silverstein, SLAC, Stanford:
The Tachyon at the End of the Universe
Andrei Starinets, Perimeter Institute:
Holography and hydrodynamics
Andrew Strominger, Harvard:
Fun with Black Holes
Shigeki Sugimoto, Yukawa Institute for Theoretical Physics, Kyoto:
Analysis of QCD via Supergravity
Tadashi Takayanagi, Harvard:
Time-like Linear Dilaton and Open-Closed Duality
Alessandro Tomasiello, ITP, Stanford:
The Generalized Complex Geometry of Supersymmetry
Henry Tye, Cornell:
Wavefunction of the Universe
Angel Uranga, Universidad Autónoma de Madrid:
Infrared dynamics of duality cascades and warped throats
Erik Verlinde, ITF, Amsterdam:
A Matrix Big Bang
Edward Witten, IAS:
Axions in String Theory
Shing-Tung Yau, Harvard:
Superstring theory with torsion
Barton Zwiebach, MIT:
Is there a closed string tachyon vacuum?
==endquote==

 

[marcus]

Right now Nekrasov is giving his talk and I was trying to listen to the live audio stream. But the audio keeps going out, like a loose connection.

College Station is in East Texas, near Houston TX. So the timezone is Central Usa.
Two hours ahead of Pacific, so in Texas it is now 11:40 in the morning
Witten's talk begins around 12:10. In just a few minutes.

Too bad about their audio breaking up all the time---or maybe it is just my server's fault.

If you want to try to listen, go here:
http://mitchell.physics.tamu.edu/Conference/string2010/index.html
and see where it says "webcast with live streaming"
and click on "webcast".

AFAICS it is pretty minimal. They don't have video, at least at this point, and there is no indication that stuff is being archived. And there is no sign of online slides PDF. But that presumably could change.

 

[marcus]

I just listened to the whole Witten talk, from 12:10 to 12:55 Texas time.
My impression is it lends credence to something Physicsmonkey said earlier in this thread.

The talk was incredibly 4D but also incredibly stringy.

He often reiterated that he was working on a 4D manifold M. And then sometimes he went DOWN to even lower dimension, like 2D, by for instance compactifying.
The talk was extremely background DEpendent. The 4D manifold M was sometimes set up to be a 3sphere X R, or sometimes it was a 2D cylinder surface X something, or sometimes it had a toroidal (donut surface) component. By introducing symmetries in the underlying space you could to mathematical tricks with fields defined on it.

So, it was very different from Witten's Strings 2007 talk about mere 3D Quantum Gravity. That 2007 talk surprised some people because it was so unstringy. Someone at the end asked him a question like "but what about string theory?" because he hadn't talked enough string shop during the talk. But this 2010 talk was quite different!

There were no questions after, because it was time for lunch. And although the dimensionality was chopped down to what I'd call "toy" model levels, the vocabulary was heavily string.

Also MTd2, notice that the work Witten talked about involves a LOT of people. Including three others Nekrasov Tachigawa and Gaiotto who had each already given papers about it at the conference. And he was constantly referring to other people as well
The themes of Omega background, and N=2 or N=4 super YangMills in 4D.

This all presents a riddle. What has led to this convergence on 4D? Using elaborate string math methods. Physicsmonkey suggests that it was simply that "the math led them to 4D".
That is possible but why and how. Or is this merely toy-modeling. Work something out in lower dimensionality and then jack it up to 11D or whatever. It doesn't come across that way, but it could be.

Now it is getting close to 14:10 Texas time, and Strominger will be talking. Strominger is another one whose talk is 4D this time, if we go by his arxiv paper with the same title.
But it doesn't seem to be part of the cluster of papers that Witten was talking about. He is coming from a different direction.

===============
EDIT well, the live streaming audio is kaput again. It was OK all thru Witten's talk this morning but it broke up sporadically with Nekrasov and now, at the moment, it is completely out for Strominger.

 

[Haelfix]

Wittens focus is on Geometric Langlands, that's the primary motivation for the admittedly technical paper.

It uses stringy or semi stringy math (generalized quiver diagrams) to analyze a toy model of the more general correspondance, trying to get a physics foothold into the subject.

The hope is twofold.. One is an eventual 'physics' proof of the duality, and conversely a language/dictionary that interpolates between geometric Langlands and certain integrable systems, where you would presumably have a powerful new quantization method available for that class of gauge theories..

It should be emphasized that, at first glance this has absolutely nothing to do with phenomenology except in so far as certain of these gauge theories might eventually correspond, be dual too, or be dimensionally reduced to certain quantum systems of interest.

 

[marcus]

Well fortunately the audio came back and I was able to listen to a portion of Strominger's talk called The Kerr-Fermi Sea. As far as I could tell, it followed closely the paper by the same name:

http://arxiv.org/abs/0912.4265
The Kerr-Fermi Sea
17 pages, 1 figure
(Submitted on 21 Dec 2009)
"The presence of a massive scalar field near a Kerr black hole is known to produce instabilities associated with bound superradiant modes. In this paper we show that for massive fermions, rather than inducing an instability, the bound superradiant modes condense and form a Fermi sea which extends well outside the ergosphere. The shape of this Fermi sea in phase space and various other properties are analytically computed in the semiclassical WKB approximation. The low energy effective theory near the black hole is described by ripples in the Fermi surface. Expressions are derived for their dispersion relation and the effective force on particles which venture into the sea."

This paper is about objects in the real world, not about extra dimensions and fancy mathematics. It is of general interest to Relativists who model realworld black holes. At the end of his talk he got right down to considering if the effects of this sea could be observed. The black hole does not have to be extremal, his analysis extends down to low angular momentum---but the lower the spin, the less the effect and the Fermi sea becomes negligible.

 

[marcus]

Strings 2010 doesn't seem to have gotten much notice or comment in the physics blogs. Does anyone have links to some reactions from those attending? Comment from string theorists or possibly from some non-string physicists who might have been in the audience?

Today I was listening to part of Dieter Lüst's talk and heard him mention that his group at Munich intends to host Strings 2012. That might be an interesting conference, in part because there could finally be some statistically significant results from LHC. Whether or not they have any real bearing on supersymmetry or on superstrings, LHC data could be stimulating some new ideas, by that time.

What do you make of this blog comment from a heavy ion physicist who was attending Strings 2010 at College Station, TX?
==quote==
lun says:
March 17, 2010 at 4:25 pm
As a heavy ion physicist with an interest in AdS/CFT, the presentations I saw absolutely shocked me.

The tone of the speakers, and I am talking about the leading lights of string theory, was essentially “we learned everything there is to learn about heavy ions, so we are not interested in it anymore, let us do condensed matter physics”.

While AdS/CFT was, and still is, a promising field, its “objective” impact to understanding the system created at RHIC is zero: I mean, there are neat calculations of highly idealized models, but there is no evidence that these models actually apply to the real world. Worse than that, there was very little effort to _look_ for this evidence. For the string theorists to now behave as if the job is finished, and they can concentrate on something else, is simply preposterous. It would be bad enough to admit failure (its premature, this approach has potential!), but they behave as if it was an unqualified success (and surely enough, PR annoucements will continue to claim this). Heavy ion phenomenologists (not to speak of the experimentalists) have every right to be extremely annoyed at this attitude.

No idea how the condensed matter community will receive this interest. The people I know working on high-Tc superconductivity and related problems (a sample of ~5) have either never heard of AdS/CFT, or are dismissive of it. From my admittedly naive outsider perspective, the models described in the talks are largely too “artificial” to teach us anything we do not know already (in comparison the heavy ion models are actually pretty simple and natural, something I have in the past found very attractive), so it looks very much a repeat of the heavy ion performance: A few technical calculations of models that “look like” the system they claim to represent, little phenomenological effort, and a lot of PR.

Honestly, if this is the best the field can offer, we are in deep trouble.
==endquote==
http://www.math.columbia.edu/~woit/wordpress/?p=2794&cpage=1#comment-53886

 

[MTd2]

Where is this blog?

 

[MTd2]

Oh, that's just Peter Woit's blog. What can I say? If that's what he thought, string theorists should just for another job.

 

[marcus]

The comment is by Lun, who says his field is Heavy Ion Physics. I have never seen any comment by him before at Woit's blog. My guess is that he must have had a very positive hopeful attitude toward String, to have even caused him to fly out to east Texas to attend the conference in the first place. And his comment suggests that, in fact, he was expecting some of the presentations to be relevant to RHIC research.

But was disappointed.

 

[marcus]

I just listened to portions of talks by Weinberg, Horava, and Lance Dixon.
Weinberg's was the most interesting talk of the conference, for me. And the most nonstringy.
He highlighted recent work by Benedetti Machado Saueressig, and also by Niedermayer. He got more and livelier questions after the talk than any speaker I heard all week, with the most exciting 5 minutes of the conference being a rapid-fire Q&A between Weinberg and Edward Witten.

Witten seemed seriously interested by Weinberg's talk, and jumped right in with questions. The two seemed to immediately understand each other so no time was wasted on hem and haw. Good to hear that level of engagement.

Weinberg pointed out unresolved issues with the Asymptotic Safe gravity approach. We should not take for granted. However: "there's no question Newton's constant runs." And
"effective field theory may be all there is up to arbitrarily high energy."

He was especially interested in applying A.S. to cosmology. It isn't clear yet that the conjectured explanation of inflation will work. If we follow Benedetti Machado Saueressig analysis, there would not be enough "e-foldings" of inflation produced by the running of the constants. Some inflationary episode but ending too soon. Needs work, but judged worth investigating.
=============
Horava said explicitly that his approach is indeed a "plan B to string theory". In other words a lifeboat in case of trouble with the ship of string. But he emphasized the common elements, how techniques could be carried over, so he presented it as an attractive transition path for emigré string theorists. A new but not altogether unfamiliar line of research that some could shift over into.

 

[MTd2]

Did horava say something about his work with Cenke Xu, the one where he cites CDT?

http://arxiv.org/abs/1003.0009

There is a discussion about it here:
https://www.physicsforums.com/showthread.php?t=382873

 

[marcus]

Did horava say something about his work with Cenke Xu, the one where he cites CDT?

http://arxiv.org/abs/1003.0009

There is a discussion about it here:
https://www.physicsforums.com/showthread.php?t=382873

Yes! He made much of the apparent kinship with CDT, and he said some quite favorable things about CDT, but I cannot quote verbatim. He likes it.

 

[MTd2]

So, Witten has basically gave up on strings?

 

[marcus]

"give up"? I don't see how anyone could say that!

A complex creative mind can set one interest aside and turn to another, and then again. We can't see into each other's minds.

I take him at face value, what he says. In 2006 he came out to UC Berkeley to give a series of 3 talks, each 90 minutes, about his research interest, which was Geometric Langlands. I attended all three talks and he spoke for 270 minutes without mentioning string theory.

Then at the end of the last talk, it occurred to someone to wonder "what about string theory?" And so they raised their hand and asked, when it was time for questions. He put them off with a one-sentence reply.
"Oh! I still hope that string theory will turn out to have something to do with Nature."

I see no reason not to believe that he expressed his inner state of mind precisely, and that he still feels the same way. I have not heard anything to the contrary.

Plus there is some very interesting mathematics! And a mathematician does not "give up" on some inherently interesting mathematics whatever the connection or non-connection with Nature.

However I could be wrong. If you hear anything that suggests to you that Witten's enthusiasm for string is less than it was, say, in 2006 when I heard him talk, that would be interesting I suppose, so please let me know.

He is not the most important bellwether in the string community now, however, IMHO. I think it is the younger ones, under 40, who lead now, and it is them that we should be watching. Witten's influence may be exaggerated.

 

[MTd2]

I was just kidding!

 

[marcus]

Oh, just kidding. I see
Well the answer is that what Witten does or doesn't do is not so important now, but he hasn't shown much real interest in string since around 2006.

In 2007 he gave a talk at Strings 2007 that wasn't about string---it was 3D quantum grav.
He didn't attend Strings 2008.
He gave no paper at Strings 2009, but delivered an evening lecture to the public, that was not about string. And also in 2009 gave a major perspective talk at CERN about the future of physics "away from the high energy frontier" which barely mentioned string.
Practically speaking he has made it clear to the string community that he is a free agent and that they can't exactly count on him. On the other hand there continue to be attractive projects in string mathematics...

 

[marcus]

MTd2 I think your "just kidding" reference to Witten might distract readers. I didn't think his talk was all that interesting or important. We should try to focus on what we can learn from the conference. Weinberg's talk got a lively response. It was probably the most interesting talk that day, maybe the whole week!

I'll copy my post about it, to refresh the memory.

I just listened to portions of talks by Weinberg, Horava, and Lance Dixon.
Weinberg's was the most interesting talk of the conference, for me. And the most nonstringy.
He highlighted recent work by Benedetti Machado Saueressig, and also by Niedermaier. He got more and livelier questions after the talk than any speaker I heard all week, with the most exciting 5 minutes of the conference being a rapid-fire Q&A between Weinberg and Edward Witten.

Witten seemed seriously interested by Weinberg's talk, and jumped right in with questions. The two seemed to immediately understand each other so no time was wasted on hem and haw. Good to hear that level of engagement.

Weinberg pointed out unresolved issues with the Asymptotic Safe gravity approach. We should not take for granted. However: "there's no question Newton's constant runs." And
"effective field theory may be all there is up to arbitrarily high energy."

He was especially interested in applying A.S. to cosmology. It isn't clear yet that the conjectured explanation of inflation will work. If we follow Benedetti Machado Saueressig analysis, there would not be enough "e-foldings" of inflation produced by the running of the constants. Some inflationary episode but ending too soon. Needs work, but judged worth investigating.
=============
Horava said explicitly that his approach is indeed a "plan B to string theory". In other words a lifeboat in case of trouble with the ship of string. But he emphasized the common elements, how techniques could be carried over, so he presented it as an attractive transition path for emigré string theorists. A new but not altogether unfamiliar line of research that some could shift over into.

And then the topic of HOLOGRAPHIC SUPERCONDUCTIVITY has definitely been hot. A lot of people have started working in that area, and gave papers on it.

I think we are seeing a variety of "exit strategies" being presented. Good things for string theorists to work on that are more in the direction of 4D and/or real world. Yet have some carry-over in terms of math techniques---some familiar aspects.

I'm hoping to see more of these "bridges" that will allow string theorists to put their skills to use and steer their careers in more productive directions in the coming years.

Horava's move is kind of ideal in this respect, and he has a lot of followers. Another hopeful sign, IMHO, what Andy Strominger is doing. He is studying real 4D black holes, at least in part, and finding out new stuff. He could go to GR19 and present his Fermi sea paper to the regular GR research community, if he chose to, I think. He is not just a string theorist any more. It would be good if more of them developed that kind of breadth, don't you think?

 

[MTd2]

He is not just a string theorist any more. It would be good if more of them developed that kind of breadth, don't you think?

I think it is great when people start thinking like t'Hooft! Never get attached to any concept as fundamental, like quantum mechanics! Thinking outside the box, instead of clinging to a concept, such as string theory, when we still do not have the means to test it.

It would be a huge win for all theoretical physics if Witten discussed any physics that didn't have any supersymmetry in it.

I like the fundamental of things, like the manufacture of transistors of computers and concepts of nature. So, I didn't take interest in the Kerr-Fermi sea. But is there anything fundamental there?

 

[marcus]

... So, I didn't take interest in the Kerr-Fermi sea. But is there anything fundamental there?

i'm not necessarily the person to ask, and I hope some other(s) may respond. But as far as I know NOT. But I think it has empirical potential. There could be observable consequences. We have to respect anybody who can derive some new observable phenomena from quantum gravity models, or even from classical black hole models. It is such a deep and difficult problem, any kind of authentic phenomenology deserves consideration.

So I think it is maybe not fundamental particle physics, but at this point in history it might turn out to be as important as a modest particle theory innovation might be.

Why wouldn't Strominger get in touch with Bee Hossenfelder, who is running a QG phenom conference this summer? Are these people all so fragmented they don't talk to each other?
Why wouldn't Strominger contribute a presentation to GR19 in Mexico City this July?
I want to see some getting together and some crossing of lines.

 

[MTd2]

The slides of many of the talks are already available:

http://mitchell.physics.tamu.edu/Conference/string2010/TitleofTalks.html

 

[MTd2]

Horava and Weinberg's talk are already available:

http://mitchell.physics.tamu.edu/Conference/string2010/documents/slides/Weinberg.tamu10sw.pdf

http://mitchell.physics.tamu.edu/Conference/string2010/documents/slides/Horava.tamuP4.pdf

Ha! Horava cited Benedetti, Loll, Jacobson and Verlinde!

BTW, his talk have totally new content!

 

[yoda jedi]

string and loop are dead.

 

[petergreat]

string and loop are dead.

My uninformed guess is that string theory won't eventually die unless the LHC 1)Finds no supersymmetry 2) Finds no extra dimension 3) More importantly, finds something completely new which has nothing to do with string theory (4th generation?), so people get distracted away from strings and jump on some new bandwagon.

Another possibility is that the Planck Satellite, soon to release data, discovers some crazily non-Gaussian CMB, so people flow from particle theory to cosmology. Although some aspects of cosmology are also depressing. For example they have been chasing the idea of cosmic strings since the time people didn't know about string theory, but such objects still have no experimental proof. Inflation remains a field which promotes wild guesses about its cause, but no one can convince others.

 

[yoda jedi]

astrophysical high energy photons.