# String theory today

1. Jul 11, 2012

### marcus

Each year, the annual String conference provides us with a kind of snapshot of the field as it is today. The lineup of invited speakers and the titles of their talks give an idea of the current activity and interests of string researchers.

This year Strings 2012 is in Munich and starts on Monday 23 July. The organizers plan to have 45 talks. As of today titles of 16 of the 45 are listed.

F. Alday Mixed correlators in N=4 SYM
T. Dimofte Building blocks in 3d SCFT
M. Gaberdiel Minimal Model Holography
G. Horowitz Why General Relativity is like a High Temperature Superconductor
N. Iqbal Friedel oscillations and horizon charge in 1D holographic liquids
A. Karch Recent Applications of the Gauge/Gravity Correspondence to QCD and Condensed Matter Physics
S. Kortner Status and latest results of the LHC
H. Nicolai Alternative approaches to quantum gravity: a brief survey
H.P. Nilles Heterotic supersymmetry: the legacy of D=10 and N=4
S. Raju Scattering Amplitudes and AdS/CFT Correlators
J. Schwarz Opening Lecture
A. Strominger Progress in dS/CFT
A. Uranga Update on string phenomenology
E. Witten Superstring Perturbation Theory Revisited
M. Yamazaki Networks, Quivers and 3-manifolds
X. Yin Higher Spin Holography

Overall attendance figures for some past conferences. In several cases (e.g. Madrid) a cap was placed on attendance and registration was only allowed up to a certain limit:

Registered participants in the annual conference (some years omitted for brevity)
Code (Text):
Strings 2003 Kyoto     396
Strings 2005 Toronto   415
Strings 2009 Rome      450
Strings 2011 Uppsala   265
Strings 2012 Munich    384 (prelim.)

So far 384 people have registered to attend the conference, of which roughly half are listed as "student", "graduate student", "PhD student", or "postdoc."

The state of the field is also reflected in what kinds of theorists physics departments are most interested in hiring: e.g. which particle theory specializations (cosmology, phenomenology, string, lattice...) currently figure most prominently. The particle theory job picture for this year (Usa + Canada, first-time faculty positions) is the same as it was 8 June, over a month ago. Twelve HEP theorists have offers, of whom one is a string theorist. Faculty hiring for the fall semester could still change but now seems approximately complete for the year.

Annual first time faculty hires in theoretical particle physics (Usa + Canada)
(Up through 2010, the rates are averaged over 3 years intervals.)
Code (Text):

period          1999-2001   2002-2004   2005-2007   2008-2010  2011   2012
HEP theory hires   18         24          23          13        11     12
string hires        9          8           6           2         1      1
The source used for the preliminary 2012 estimates: http://particle.physics.ucdavis.edu/rumor/doku.php
Source for previous years: http://www.physics.utoronto.ca/~poppitz/Jobs94-08

Last edited: Jul 11, 2012
2. Jul 11, 2012

### Mark M

Great job putting this together. Of the talks currently listed, the two that look most interesting to me are Strominger's talk on dS/CFT, and Uranga's talk on string phenomenology.

3. Jul 11, 2012

### marcus

Thanks! I tend to agree with you. Phenomenology is the key area, a kind of information bottleneck, and any development there would be highly significant. Also Strominger (I have a high regard for him) often gives one of the more interesting talks at the annual conference. In this case the restriction to AdS has been a major handicap for something like 10 years. Given the apparent positive cosmo constant they in some sense HAVE to break out of the AdS trap. So (IMHO as nonexpert observer) everybody is going to be interested by what he presents.

Here is the website's speaker list with titles posted so far:
http://wwwth.mpp.mpg.de/members/strings/strings2012/strings_files/program/talks.html
We can check back periodically with this link to see how it shapes up as more talk titles are added.

I also find it interesting that Hermann Nicolai (another of my favorite string people) is giving a survey talk on non-string QG alternatives. The organizers apparently thought this topic would interest those attending the conference.

Last edited: Jul 11, 2012
4. Jul 11, 2012

### Mark M

I wonder if Strominger will make any mention of the result of Hawking/Hartle/Hertog. That is, the paper in which they attempted to show that a negative cosmological constant would result in a positive acceleration of expansion.

Another talk that looks interesting is the one that will be given by Kortner regarding the latest results at LHC.

5. Jul 14, 2012

### marcus

I think he almost has to make some reference to that paper---the authors are so prominent.
You're right about the Kortner talk, it's likely to be well worth watching!

I'll do an update on the conference while I'm at it. About a week to go. Registration is at 384, half are listed as grad student, postdoc and the like.
As of today titles of 24 of the 45 planned talks are listed. The strongest common theme appears to be CFT-based holography, i.e. gauge/gravity correspondence and its applications. To show thematic emphasis I've highlighted the CFT/holo talks:

M. Aganagic Knots, Mirror Symmetry and Large N Duality
F. Alday Mixed correlators in N=4 SYM
M. Cvetič Non-perturbative Effects in F-theory Compactifications
T. Dimofte Building blocks in 3d SCFT
M. Gaberdiel Minimal Model Holography
D. Gross Outlook/Vision
G. Horowitz Why General Relativity is like a High Temperature Superconductor
N. Iqbal Friedel oscillations and horizon charge in 1D holographic liquids
A. Karch Recent Applications of the Gauge/Gravity Correspondence to QCD and Condensed Matter Physics
S. Kachru New Horizons in Finite Density Field Theory and String Theory
S. Kortner Status and latest results of the LHC
H. Nicolai Alternative approaches to quantum gravity: a brief survey
H.P. Nilles Heterotic supersymmetry: the legacy of D=10 and N=4
H. Ooguri Conference Summary
E. Rabinovici (In) Stabilities and complementarity in AdS/CFT
S. Raju Scattering Amplitudes and AdS/CFT Correlators
O. Schlotterer Hidden simplicity in superstring amplitudes
J. Schwarz Opening Lecture
A. Strominger Progress in dS/CFT
A. Uranga Update on string phenomenology
C. Vafa Topological Strings and Their Diverse Applications
E. Witten Superstring Perturbation Theory Revisited
M. Yamazaki Networks, Quivers and 3-manifolds
X. Yin Higher Spin Holography

Strings 2013 will be held in Seoul, June 24-28.

Last edited: Jul 14, 2012
6. Jul 14, 2012

### Mark M

Great job again with the update.
I'm curious about what he'll have to say, considering the lackluster performance of string theory over the past few years.

7. Jul 15, 2012

### tom.stoer

Have a look at these slides from "string 2007" and "strings 2009":

http://strings2009.roma2.infn.it/talks/Gross_Strings09.pdf, slide #16
http://www.ift.uam.es/strings07/040_scientific07_contents/transparences/gross.pdf [Broken], slide#22

where Gross asked some interesting questions - on which he probably is still waiting for reply:

WHAT IS STRING THEORY?
This is a strange question since we clearly know what string theory is to the extent that we can construct the theory and calculate some of its properties. However our construction of the theory has proceeded in an ad hoc fashion, often producing, for apparently mysterious reasons, structures that appear miraculous. It is evident that we are far from fully understanding the deep symmetries and physical principles that must underlie these theories. It is hoped that the recent efforts to construct covariant second quantized string field theories will shed light on this crucial question.

We still do not understand what string theory is.
We do not have a formulation of the dynamical principle behind ST. All we have is a vast array of dual formulations, most of which are defined by methods for constructing consistent semiclassical (perturbative) expansions about a given background (classical solution).

What is the fundamental formulation of string theory?

WHAT IS MISSING ?
Perhaps “String theory” is like quantum field theory - a framework and not a definitive theory.
Perhaps we are missing a fundamentally new principle of symmetry, of dynamics, of consistency, .... that leads to a unique solution --- not a “vacuum” but a space-time, a cosmology.
Emergent Space-Time

Last edited by a moderator: May 6, 2017
8. Jul 15, 2012

### Blackforest

Unfortunately, I have no holydays next week... I would have appreciate to ear some of the conferences. My preference goes to G. Horowitz. Do you know if outsider like me can get abstracts from a part of the conferences?

9. Jul 15, 2012

### marcus

I hope and expect that video of all the talks will eventually be freely accessible online.
This is how it was last year when the Strings 2011 conference was held at Uppsala Sweden.

I'll do an update on the conference while I'm at it. Next year's Strings will be held in Seoul, June 24-28, 2013. Strings 2012 starts Monday 23 July. Registration at 384, about half being grad student, postdoc and the like. A prevalent topic appears to be CFT-based holography so I've highlighted the CFT/holo talks. As of today, titles of 28 of the 45 planned talks are listed.:

M. Aganagic Knots, Mirror Symmetry and Large N Duality
F. Alday Mixed correlators in N=4 SYM
J. Carrasco Generic multiloop methods for gauge and gravity scattering amplitudes, a guided tour with pedagogic aspiration
A. Castro Path integrals in 3D gravity
M. Cvetič Non-perturbative Effects in F-theory Compactifications
T. Dimofte Building blocks in 3d SCFT
M. Gaberdiel Minimal Model Holography
D. Gross Outlook/Vision
G. Horowitz Why General Relativity is like a High Temperature Superconductor
N. Iqbal Friedel oscillations and horizon charge in 1D holographic liquids
S. Kachru New Horizons in Finite Density Field Theory and String Theory
A. Karch Recent Applications of the Gauge/Gravity Correspondence to QCD and Condensed Matter Physics
S. Kortner Status and latest results of the LHC
H. Nicolai Alternative approaches to quantum gravity: a brief survey
H.P. Nilles Heterotic supersymmetry: the legacy of D=10 and N=4
H. Ooguri Conference Summary
A. Polyakov Quantum Instability of the de Sitter space
E. Rabinovici (In) Stabilities and complementarity in AdS/CFT
S. Raju Scattering Amplitudes and AdS/CFT Correlators
O. Schlotterer Hidden simplicity in superstring amplitudes
J. Schwarz Opening Lecture
A. Strominger Progress in dS/CFT
A. Uranga Update on string phenomenology
C. Vafa Topological Strings and Their Diverse Applications
E. Witten Superstring Perturbation Theory Revisited
M. Yamazaki Networks, Quivers and 3-manifolds
X. Yin Higher Spin Holography
B. Zwiebach Glimpses of Double Field Theory Geometry

I was intrigued by the title of Polyakov's talk: Quantum Instability of the de Sitter space
http://arxiv.org/abs/1106.1558
A String Model for AdS Gravity and Higher Spins,
I speculate that he tried to do something similar for dS space and found it didn't work. Hence a kind of negative result.

Last edited: Jul 15, 2012
10. Jul 18, 2012

### atyy

Last edited: Jul 18, 2012
11. Jul 21, 2012

### w4k4b4lool4

yes, that's an interesting paper .. you should have been at the Brussels conference a few weeks ago, where all three, namely Hartle, Hawking, Hertog, and also Strominger, Susskind, ..., among others were present:
http://www.solvayinstitutes.be/events/cosmology2012/cosmology.html [Broken]
Hartle presented the paper you are referring to. Strominger's dS/CFT talk was a bit more vague.

The above statistics make me sad by the way ...

But thanks Marcus for gathering all this interesting info in one place!

Wakabaloola

Last edited by a moderator: May 6, 2017
12. Jul 21, 2012

### marcus

You are very welcome Waka! And I am concerned that some stats sadden you.
I am sad myself about what appears to me to be too many gradstudents and postdocs in the pipeline. There is definitely demand but there is an oversupply I think. This is just my hunch since I am very far from having direct knowledge.
There are also (I think) valid research problems to work on, but with an oversupply of people there could be a fair amount of duplication.
I worry mainly about the gradstudents and postdocs, not the established people.

On a more cheerful note, if you are the flexible creative person you seem to be from a few of your posts (with subtlety and a sense of humor as well I would think) then prospects can't really be so bad. You must be primarily worried about other people. I shouldn't be so foolish as to make a wild guess like that based on superficial first-impression appearances, but there it is.

I think if I was in your shoes (as I imagine or guess the situation) I would talk to Hermann Nicolai. that might be a vacuous suggestion: you may know him and already have gotten his ideas. I think he understands the borderland areas around String and to some extent the whole map of QG. One should be prepared to be mobile and cross boundaries, not be too much limited by formalities and conventional approaches.

At the Max Born symposium in 2009, Nicolai talked a bit about some work of Shaposhnikov---he seems to me to be another "amphibian". http://www.ift.uni.wroc.pl/~planckscale/

I think the list of Strings 2012 talks is now complete. I should post a link and hope that people study the list, and think about it. Do you have any comment on the major themes that seem to be emerging? Anything new?

You mentioned Asymptotic Safety. I'm interested by that too. I'm trying to understand better how the world might look from your perspective as a string theorist with some acquaintance with bordering fields such as Loop, Asymptotic Safety, probably applied AdS/CFT and doubtless much more.

I almost forgot, cosmology. It is the testing ground for all these approaches: String, Loop, Asym. Safety, and surely several more. I think if I were young (not a retired person just watching) I would try to learn all the active approaches that bear on understanding the start of expansion and the background radiation, inflation, etc etc. Understand the "big bang/bounce" from every possible avenue and viewpoint. Try to see how to distinguish by observational testing.

Last edited: Jul 21, 2012
13. Jul 21, 2012

### marcus

The program of Strings 2012 is complete! Here is the list of talks:
http://wwwth.mpp.mpg.de/members/strings/strings2012/strings_files/program/talks.html

Let's hope there are many interesting ones and that they become available as online video, or at least as slides PDF.

I'd like very much to get other people's comment on the lineup of talks and the predominant topics.
Maybe I should paste it in:

M. Aganagic Knots, Mirror Symmetry and Large N Duality
F. Alday Mixed correlators in N=4 SYM
L. Anderson New Aspects of Heterotic Geometry and Phenomenology
I. Antoniadis Aspects of string phenomenology in the new LHC era
N. Arkani-Hamed Scattering Amplitudes and the Positive Grassmannian
C. Bachas AdS4/CFT3 and Gravity Localization
F. Cachazo Gravity in Twistor Space
J. Carrasco Generic multiloop methods for gauge and gravity scattering amplitudes, a guided tour with pedagogic aspiration
A. Castro Path integrals in 3D gravity
M. Cvetič Non-perturbative Effects in F-theory Compactifications
T. Dimofte Class R: A User's Guide
S. Dimopoulos What has the LHC done to Theory?
B. Freivogel Predictions from Eternal Inflation
M. Gaberdiel Minimal Model Holography
D. Gaiotto Domain walls and RG flows
C. Gomez Black holes as graviton condensates at the critical point of a quantum phase transition
D. Gross Outlook and Vision
J. Heckman Covariant Non-Commutative Geometry From String Theory
G. Horowitz Why General Relativity is like a High Temperature Superconductor
N. Iqbal Friedel oscillations and horizon charge in 1D holographic liquids
S. Kachru New Horizons in Finite Density Field Theory and String Theory
A. Karch Recent Applications of the Gauge/Gravity Correspondence to QCD and Condensed Matter Physics
Z. Komargodski Comments on the Renormalization Group and Diverse Applications
S. Kortner Status and latest results of the LHC
C. Kounnas Non-singular Superstring Cosmologies
J. Maldacena Constraining theories with higher spin symmetry
H. Nicolai Alternative approaches to quantum gravity: a brief survey
H.P. Nilles Heterotic supersymmetry: the legacy of D=10 and N=4
H. Ooguri Conference Summary
A. Polyakov Quantum Instability of the de Sitter space
E. Rabinovici (In) Stabilities and complementarity in AdS/CFT
L. Rastelli Bootstrapping the Superconformal Index
O. Schlotterer Hidden simplicity in superstring amplitudes
J. Schwarz Opening Lecture (I)
N. Seiberg Chern-Simons Contact Terms
E. Silverstein RG and unitarity in spacetime-dependent QFT
A. Strominger Progress in dS/CFT
A. Uranga Update on string phenomenology
C. Vafa Topological Strings and Their Diverse Applications
G. Veneziano Opening Lecture (II)
E. Witten Superstring Perturbation Theory Revisited
M. Yamazaki Networks, Quivers and 3-manifolds
X. Yin Higher Spin Holography
B. Zwiebach Glimpses of Double Field Theory Geometry

Last edited: Jul 22, 2012
14. Jul 23, 2012

### marcus

*speakers giving hour talks ("survey talks"). others have 30 minutes
http://wwwth.mpp.mpg.de/members/strings/strings2012/strings_files/program/talks.html

Monday 23
J. Schwarz Opening Lecture (I)
G. Veneziano Opening Lecture (II)
A. Strominger Progress in dS/CFT
E. Silverstein RG and unitarity in spacetime-dependent QFT
F. Alday Mixed correlators in N=4 SYM
A. Karch* Recent Applications of the Gauge/Gravity Correspondence to QCD and Condensed Matter Physics
S. Kachru New Horizons in Finite Density Field Theory and String Theory
G. Horowitz Why General Relativity is like a High Temperature Superconductor
N. Iqbal Friedel oscillations and horizon charge in 1D holographic liquids
E. Rabinovici (In) Stabilities and complementarity in AdS/CFT

Tuesday 24
X. Yin* Higher Spin Holography
M. Gaberdiel Minimal Model Holography
E. Witten Superstring Perturbation Theory Revisited
A. Castro Path integrals in 3D gravity
J. Maldacena Constraining theories with higher spin symmetry
J. Carrasco* Generic multiloop methods for gauge and gravity scattering amplitudes, a guided tour with pedagogic aspiration
N. Arkani-Hamed Scattering Amplitudes and the Positive Grassmannian
O. Schlotterer Hidden simplicity in superstring amplitudes
F. Cachazo Gravity in Twistor Space

Wednesday 25
A. Uranga* Update on string phenomenology
M. Cvetič Non-perturbative Effects in F-theory Compactifications
B. Zwiebach Glimpses of Double Field Theory Geometry
J. Heckman Covariant Non-Commutative Geometry From String Theory
L. Anderson New Aspects of Heterotic Geometry and Phenomenology

Thursday 26
S. Dimopoulos* What has the LHC done to Theory?
S. Kortner Status and latest results of the LHC
H.P. Nilles Heterotic supersymmetry: the legacy of D=10 and N=4
I. Antoniadis Aspects of string phenomenology in the new LHC era
N. Seiberg Chern-Simons Contact Terms
H. Nicolai* Alternative approaches to quantum gravity: a brief survey
B. Freivogel Predictions from Eternal Inflation
C. Gomez Black holes as graviton condensates at the critical point of a quantum phase transition
A. Polyakov Quantum Instability of the de Sitter space

Friday 27
C. Vafa* Topological Strings and Their Diverse Applications
M. Aganagic Knots, Mirror Symmetry and Large N Duality
D. Gaiotto Domain walls and RG flows
M. Yamazaki Networks, Quivers and 3-manifolds
T. Dimofte Class R: A User's Guide
Z. Komargodski Comments on the Renormalization Group and Diverse Applications
C. Bachas AdS4/CFT3 and Gravity Localization
L. Rastelli Bootstrapping the Superconformal Index
C. Kounnas Non-singular Superstring Cosmologies
H. Ooguri Conference Summary
D. Gross Outlook and Vision

Last edited: Jul 23, 2012
15. Jul 23, 2012

### marcus

All these eight people's slides PDF (or powerpoint in some cases) are now posted online.
I've looked at Strominger's and thought it was interesting. Would have liked an audio with it explaining some of the diagrams and cartoons:

A. Strominger Progress in dS/CFT
E. Silverstein RG and unitarity in spacetime-dependent QFT
F. Alday Mixed correlators in N=4 SYM
A. Karch* Recent Applications of the Gauge/Gravity Correspondence to QCD and Condensed Matter Physics
S. Kachru New Horizons in Finite Density Field Theory and String Theory
G. Horowitz Why General Relativity is like a High Temperature Superconductor
N. Iqbal Friedel oscillations and horizon charge in 1D holographic liquids
E. Rabinovici (In) Stabilities and complementarity in AdS/CFT

Also looked at Horowitz and Kachru's slides. All nice presentations. Seem to be basically about finding apps for AdS/CFT. See also Karch survey talk. (applications of gauge/gravity). Probably applied holography is the main topic for Monday.
Strominger's talk somehow bolder more ambitious---opens up wide horizon of unanswered questions about deSitter space, see the end of his talk. Just some preliminary impressions of mine. To get a better idea you should check it and some other talks out.

*Karch gave the hour talk ("overview talk") today. The other's had 30-minute slots.

Last edited: Jul 23, 2012
16. Jul 23, 2012

### tom.stoer

Let me as a question: which talks address physical isues (like quantum gravity, big bang, black holes, particles and symmetries, unification, ...) and which talks address "home-made" problems of string theory?

17. Jul 23, 2012

### marcus

That's a fascinating question!
Could you take a copy of the list in post #13 (or post #14) above
and put a star* or @ symbol beside each talk that is about a physical issue?
We could separate them out. Looking at the two lists might stimulate insights
I would very much like to see a rough division like that!

Last edited: Jul 23, 2012
18. Jul 24, 2012

### tom.stoer

marcus, as a non-expert in string theory I don't dare to answer these questions based on headlines; abstracts would be helpful

19. Jul 24, 2012

### marcus

The full set of slides of each talk seems to be posted after the talks of the day are over. So we will be able to see, day by day, which talks address the realworld problems that you mentioned. (I think.) Maybe grade them on a scale 1 to 5? Where 5 is for all out tackling what has to be done and 1 is for only solving "home made" problems?
If anybody wants, they can grade the first day talks (which have their PDF posted) and send me PM. I would keep the scoring anonymous. Or Tom you could be the scorekeeper.
Or we could set up a poll? I'm getting sleepy. It is nearly 11:30 PM. Long day. Maybe we can decide how to do this tomorrow.

I did notice that there were almost no talks about understanding how the big bang might work. There was something about non-singular cosmology which sounded like it might be.
I'll get back to this tomorrow.

20. Jul 24, 2012

### marcus

Videos are now available for the Monday talks.
http://www.theorie.physik.uni-muenchen.de/videos/strings2012/index.html

So, for example, Strominger's talk can be heard, which I expect will make the slides more comprehensible.

==============
EDIT, yes! It really does. I just watched the full talk and some of the Q&A following it.
The split screen video format is nice visually. The only drawback is you can't see a moving dot on the slide where he is pointing to something. You have to guess what part of the slide he's indicating, but that's usually possible.
It's a good talk! He makes no reference to Hartle Hertog Hawking recent paper. He's really interested in deSitter space come hell-or-high-water, and throwing everything he's got at it. Nice to see.
==============
Apparently the 30 minute timeslot the regular speakers get is supposed to be just 20 minutes for the talk leaving 10 minutes for Q&A discussion.
================
EDIT: A paper relating to Strominger's talk came out today:
http://arxiv.org/abs/1207.5517
The Wave Function of Vasiliev's Universe - A Few Slices Thereof
Dionysios Anninos, Frederik Denef, Daniel Harlow
(Submitted on 23 Jul 2012)
We study the partition function of the free Sp(N) conformal field theory recently conjectured to be dual to asymptotically de Sitter higher-spin gravity in four-dimensions. We compute the partition function of this CFT on a round sphere as a function of a finite mass deformation, on a squashed sphere as a function of the squashing parameter, and on an S2xS1 geometry as a function of the relative size of S2 and S1. We find that the partition function is divergent at large negative mass in the first case, and for small $S^1$ in the third case. It is globally peaked at zero squashing in the second case. Through the duality this partition function contains information about the wave function of the universe. We show that the divergence at small S1 occurs also in Einstein gravity if certain complex solutions are included, but the divergence in the mass parameter is new. We suggest an interpretation for this divergence as indicating an instability of de Sitter space in higher spin gravity, consistent with general arguments that de Sitter space cannot be stable in quantum gravity.30 pages plus appendices, 6 figures

Last edited: Jul 24, 2012