Causes of loss of interest in String program

[tom.stoer]

I am not so sure; I think he simply follows and continuously criticizes a way taken by a small minority of string theorists.

 

[marcus]

...Second some physicists think that discussing these problems weakens the position of the research program;... That results in supressing discussions and therefore hinders, slows down or even stops progress of science.

Third (and this is a kind of self-fulfilling prophecy) unfairly dismissing objective criticism strengthens the position of the critics. ...

Thanks Tom, excellent points! Emotional ad hom defensiveness is just another symptom.

There is, I think, some factual and useful information in this thread (and related ones) of a sort that our string-friends would do well to heed.

All the defensive noise tends to drown out the information content, so I will try to recall and summarize a few essentials.

 

[marcus]

I think any objective observer realizes that the String program is in a period of difficulty and is in flux. There is, for the time being, no clear direction.

It does not hurt the program to acknowledge this, and try to understand it. We are not playing some "I'm better than you" game of scoring prestige points. A better understanding can actually help.

I would like to understand the reasons. I can't discover them by myself although I have some guesses and suspicions. Some of the discussion in the "real disappointment" has shed unexpected light on underlying physics issues.

 

[atyy]

As we now know from relative locality, marcus is in his own momentum space with respect to "an objective observer of string theory."

 

[marcus]

As we now know from relative locality, marcus is in his own momentum space with respect to "an objective observer of string theory."

Heh heh, by the principle of relative locality, so is each one of us including you, Atyy
ABJM? Anybody for twistors? Anti-deSitter condensed matter?

One trouble seems to be that the mirror in which String looks at itself is broken into many pieces.

String experts have decided after several decades experience that one should NOT think in terms of strings and branes in a geometry with compactified extra dimensions. What is the theory if one discards the central paradigm?

 

[atyy]

Heh heh, by the principle of relative locality, so is each one of us including you, Atyy
ABJM? Anybody for twistors? Anti-deSitter condensed matter?

Yeah, but actually I'm searching for relative nonlocality

 

[marcus]

...continuously criticizes a way taken by a small minority of string theorists.

Tom, I'm curious. What is this "way taken by a small minority"?

I realize there is a general trend to abandon compactified extra dimensions, but I don't criticize this. I am actually glad to see it!

Pointing out that the program is troubled is not the same as criticizing some line of theoretical development. I don't criticize trends I see today, like getting away from explicit string/brane models. I welcome several of these visible research trends.

Maybe what you meant by the "minority way" was Anthro Landscape Multivism , but I suspect that is largely dead among the researchers now and is mainly pop-market fodder. I heartily deplore it but don't waste much time criticizing it.

My main concern is not with criticizing individual research gambits (some of which I actually welcome!) but with the fact that the program seems to have lost an overall Gestalt and direction. It needs to find its way.

 

[fzero]

String experts have decided after several decades experience that one should NOT think in terms of strings and branes in a geometry with compactified extra dimensions. What is the theory if one discards the central paradigm?

You keep saying this, but your evidence is scant. With all due respect to surprised, both Haelfix and I have explained several times now how CY compactifications are thought to be universal in the space of critical superstring CFTs. You will find very few string theorists that have "discarded the central paradigm," which is tied to a mathematical construction and particular interpretation of the degrees of freedom that it represents. At the same time, it is no doubt worthwhile to also study different formulations to find other consistent string theories. So far as I can tell from the literature, many of these theories are probably related to CY compactifications, though the connection is not as well established as for standard Gepner models. Many of the ones which are not have physically undesirable properties, such as massless fractionally charged particles.

It may very well be that there is a description of nonperturbative degrees of freedom in which spacetime geometry is less fundamental. This would not invalidate the CY description at scales sufficiently below the string scale, though it might cause us to reassess whether or not there is any physical limit in which extra dimensions are large. If there is no phase of the universe in which they are large, then it probably doesn't make sense to call them true dimensions, but we can still use the techniques of CY geometry where they apply.

 

[marcus]

With all due respect to surprised, both Haelfix and I have explained several times now how CY compactifications are thought to be universal...

Thanks fzero! I think what you are showing me is that it is controversial. Many in the String program (but not all!) have concluded that strings/branes in compactified extraD are the wrong way to go. I can't say which POV is in the majority and maybe that does not matter.

You commented about evidence. Here is some supporting evidence. This is a sample of famous stringsters whose names just happened to occur to me and to PAllen. I didnt look at their papers first before deciding to put them on the list. DESY librarians make a professional classification of papers---they decide which papers to tag "string model" and "membrane model". The indication is that the top people USED to write papers explicitly involving strings/branes and that they do that much less. Not HARD evidence, but a suggestive straw in the wind.

This seems to support what a respected Pro said here earlier about "many" String people. I'll not paraphrase since I might unintentionally err. But I would say this suggests that among the top people there has been a huge shift out of explicitly string/brane research proper. If you want the Spires links, go back to post #63.

          1995-1998      1999-2002      2003-2006      2007-2010
Witten         38             29              9              5
Strominger     23             14             22              4
Maldacena      27             33             24              9 
Polchinski     21             17             11              4
Harvey,J       16             15              9              2
Duff,M         24             17              8              5
Gibbons,G      17             29             11              2
Dijkgraaf      18             11              9              7
Ooguri         31             18             13              8
Silverstein,E  16             15             16             10
Seiberg,N      19             16             22              1

One wants to ask how one characterizes what these people are working on NOW. Is there a coherent form and direction to it? What is the String program about if you ditch parts of the core paradigm?
Or "de-emphasize" if you prefer.

I can't avoid noticing that the big decline happened 2003-2006, which is also when there was a huge drop in overall String-of-any-kind representation in the Spires Top-cite Fifty.

And those sharp drops happened right after the 2003 KKLT paper and Susskind's IMHO panicky reaction to it. There could be no connection but it could be argued that these things that surfaced in 2003 MIGHT have something to do with those changes in research focus and ratings.

 

[fzero]

Thanks fzero! I think what you are showing me is that it is controversial. Many in the String program (but not all!) have concluded that strings/branes in compactified extraD are the wrong way to go. I can't say which POV is in the majority and maybe that does not matter.

This is incorrect. There are a handful of groups studying alternatives and much of the results in this direction are by two separate groups involving Faraggi and collaborators and Schellekens and collaborators. The vast majority of model building papers focus on CY compactifications (the U Penn and Lust groups are representative).

You commented about evidence. Here is some supporting evidence. This is a sample of famous stringsters whose names just happened to occur to me and to PAllen. I didnt look at their papers first before deciding to put them on the list. DESY librarians make a professional classification of papers---they decide which papers to tag "string model" and "membrane model". The indication is that the top people USED to write papers explicitly involving strings/branes and that they do that much less. Not HARD evidence, but a suggestive straw in the wind.

I've tried to explain multiple times why the DESY keywords cannot be completely trusted. In some cases they are correct, in others they are misleading. Since I was looking at recent Lust papers, here's another example: http://www-library.desy.de/cgi-bin/spiface/find/hep/www?eprint=arXiv:1007.5254 . The paper is a model-independent analysis of production of the lightest massive string states in intersecting D-brane models. DESY has chosen not to label it as "string model" or "brane model," though it is certainly objectively within one or both of those classes. There is no substitute for having an expert actually looking at the paper to decide what it is about. As far as I understand the DESY process, this is supposed to be done to some extent, so perhaps the errors are due to a subjective analysis of the best N keywords and others are left off.

In any case, DESY keywords not withstanding, many string theorists are working on topics such as AdS/CFT that are not model building, or otherwise exploring topics in gauge theories that may or may not be string inspired. The best that can really be said without asking these people directly is that they're working on topics which are more interesting and directly productive for them than others. The choice of research topics is often not decided by which are the most important problems, which are usually very difficult, but also by the requirement to publish, both to secure funding and jobs for younger collaborators. Also, most ideas do not survive to be published. Looking at publications does not show you what topics were pursued and abandoned as incorrect or incomplete.

Since most physicists do not publish their thoughts on broad topics not directly related to their technical publications, it isn't possible to rely on paper titles or DESY keywords to tell what they think. As I've mentioned previously, one place in which physicists do lay out their broad beliefs is in grant applications. Most of the NSF funded proposals are a matter of public record, so you could look some of those up and see if there's evidence there that most string theorists have abandoned the possibility that strings might be the correct description of nature. I believe that the vast majority of these grants will include language such as "string theory remains the best candidate for a theory that unifies general relativity and the Standard Model of particle physics," independent of what precise topics are being directly proposed.

 

[fzero]

This seems to support what a respected Pro said here earlier about "many" String people. I'll not paraphrase since I might unintentionally err. But I would say this suggests that among the top people there has been a huge shift out of explicitly string/brane research proper. If you want the Spires links, go back to post #63.

In post #24, I made a detailed analysis of Witten's publications, being very conservative about which papers should be considered string theory. There was no evidence that he had shifted out of string theory.

You are free to quibble over what constitutes string theory proper by using some keywords that are associated to model building papers. In this regard, the vast majority of papers since 1995 are not about string theory proper. Even the string duality papers of 1995 and beyond were not strictly about model building, but were about much more abstract topics.

I'm sure that you would see a similar phenomenon if you were to study lattice gauge theory papers over the last 2 decades. A certain reasonably large fraction might be about explicit calculations of hadronic mass spectra, but an equally large fraction would be about technical details or [STRIKE]unphysical[/STRIKE] nonphenomenological models that still have something to teach us about harder problems.

 

[marcus]

...
I've tried to explain multiple times why the DESY keywords cannot be completely trusted. In some cases they are correct, in others they are misleading...

No indicator is perfect. I see a huge decline and I doubt that there is a conspiracy on the part of the librarians to engineer a systematic misclassification.
This is informal of course---suggestive straws in the wind that can contribute marginally to trends many of us acknowledge.

==quote fzero==
... many string theorists are working on topics such as AdS/CFT that are not model building, or otherwise exploring topics in gauge theories that may or may not be string inspired...
==endquote==
RIGHT! Thanks for acknowledging this!

This is a large part of the point I wanted to make in this thread. There has been a major shift in research activity---sometimes I refer to it as research "interest" but what I'm looking at is objective stuff like citation counts and papers written and what topics get featured at the annual Strings 2010 or 2011. At least quality-wise, in terms of highly cited papers, there has been a decline of activity in core areas of the program.

Naturally one wants to know why. And what the new picture is that is taking shape.

I see that you have offered some reasons for the shift of research attention by "many string theorists". This is just the sort of thing that I was looking for in this thread---hopefully some objective physics reasons, but basically any kind of cause whatever that may have contributed to the observed change.


BTW may I assume you mean the grant requests that people put in for funding? Not the grants themselves but the grant proposals?
==quote==
I believe that the vast majority of these grant [proposals] will include language such as "string theory remains the best candidate for a theory that unifies general relativity and the Standard Model of particle physics," independent of what precise topics are being directly proposed.
==endquote==

 

[fzero]

This is a large part of the point I wanted to make in this thread. There has been a major shift in research activity---sometimes I refer to it as research "interest" but what I'm looking at is objective stuff like citation counts and papers written and what topics get featured at the annual Strings 2010 or 2011. At least quality-wise, in terms of highly cited papers, there has been a decline of activity in core areas of the program.

Naturally one wants to know why. And what the new picture is that is taking shape.

Like I said in my other post, even many papers written from 1995-2000 probably do not fit into the narrow area of string theory proper that you want to apply to recent papers. If you wanted to discuss a couple of papers for comparative purposes, I could probably help. Otherwise it's hard for an expert to objectively say that a particular paper on say heterotic/type II duality is more or less a core string paper than one that examines a new facet of the AdS/CFT correspondence. Neither one is probably telling us that there are three generations of matter or what the electron mass is, but both are probably saying something deep about the core theory anyway.

BTW may I assume you mean the grant requests that people put in for funding? Not the grants themselves but the grant proposals?

Yes, if you go to http://www.nsf.gov/awardsearch/ you can obtain information about grants awarded. This includes the investigators, the institution, and the abstract included in the grant proposal, among many other sundry details. Full proposals are not distributed (which would contain details of ongoing research that should really be kept confidential for many reasons), but the abstracts are probably still useful for the suggested purpose.

 

[unusualname]

yawn, yet more attacks on marcus and his perfectly reasonable attempts to portray the modern research programs in fundamental physics,

geez, you string guys had your time, we got it, fundamental reality might be 1d oscillating strings, or it might be 0d branes (ie points ala feynman e^i.theta) or it might be higher dimensional branes.

yawn again. maybe you're just partially correct like everybody else, maybe all that oh so friggin difficultly constructed mathematics will fit in , but it's a convoluted way to construct reality.

Just sayin'

 

[smoit]

In post #24, I made a detailed analysis of Witten's publications, being very conservative about which papers should be considered string theory. There was no evidence that he had shifted out of string theory.

It does not matter for him, fzero! He'll keep ignoring this point over and over and over again because it does not fit his agenda. He'll copy and paste a part of your response that he finds useful to promote his propaganda. Marcus has reposted his "data analysis" about 10 times now, while fzero's much more careful estimate is buried in the middle of the thread. This is a classic strategy - "If you repeat a lie often enough, it becomes the truth." The end result is that some lay people will be left with impression that there is indeed some decline, not because Marcus is right, but because he's better at repeating the garbage. At the same time, in a different thread, Marcus is promoting an idea that some papers on the theory of angular momentum, computing 12j and 15j symbols, constitute research on LQG :rofl: . Any well informed person realizes how ridiculous that is but it does not matter.

I will say where I am coming from, regarding these issues. I think Final Theory is a wild goose El Dorado. Physics must be pragmatic and incremental. ...

So any theory of gravity must at least include a positive cosmological constant. Like the classic gravity equation does. I'm happy to be contradicted on this and be given counterarguments, but this is where I am coming from. String program leaders misguide the program if they do not confront this---and maybe they already do and I just didn't hear about it.

They do not confront what? The positive cosmological constant? Have you ever looked at the title of the KKLT paper, which came out in 2003? FYI, it it called "de Sitter vacua in String Theory".

 

[smoit]

As I said before, this whole "discussion" and "data mining" is directed towards the uninformed souls, interested in BSM physics, in an attempt to steer them away from string-oriented research by convincing them that there is some decline in the String program.
Below is the very reason for why this and similar threads with data "confirming" the thread title were started in the first place.

But I'm not convinced of your general statement that anyone interested in QG shoud first study String.
...
If someone is interested in QG they might do well to go to Penn State's Institute for Gravitation and the Cosmos and talk to Abhay Ashtekar. They might do well to learn some cosmology and quantum cosmology. And also get some handle on the current and projected job terrain.

Really, Marcus? Is that what it's all about? Seriously, until you change your criteria and follow fzero's suggestion for a more accurate analysis, instead of repeating the garbage, your point is moot. I'm sure that suprised, Haelfix, fzero and other reputable people on this forum see the same thing, they are just a bit more diplomatic in expressing their frustration with what you've been doing here. I'm much more blunt b/c I can't stand the BS you are spreading.

 

[unusualname]

As I said before, this whole "discussion" and "data mining" is directed towards the uninformed souls, interested in BSM physics, in an attempt to steer them away from string-oriented research by convincing them that there is some decline in the String program.
Below is the very reason for why this and similar threads with data "confirming" the thread title were started in the first place.

Really, Marcus? Is that what it's all about? Seriously, until you change your criteria and follow fzero's suggestion for a more accurate analysis, instead of repeating the garbage, your point is moot. I'm sure that suprised, Haelfix, fzero and other reputable people on this forum see the same thing, they are just a bit more diplomatic in expressing their frustration with what you've been doing here. I'm much more blunt b/c I can't stand the BS you are spreading.

You really are a very rude person.

This type of speech will look funny in restropect when the dust settles, you should reign in your vitriol so as not to appear too ridiculous,

 

[smoit]

You really are a very rude person.

This type of speech will look funny in restropect when the dust settles, you should reign in your vitriol so as not to appear too ridiculous,

Thanks for the complement! What really looks ridiculous in retrospect is this quote from 2004 addressed to a student (note the ridiculous hype of LQG in the quote below and contrast this to his tone in this thread):

Hello Tom I hope you had a good summer. You are heartily welcome to read some LQG with me in spare moments as long as you are spending enough time on a well-rounded realworld program.

...

the reason LQG is heating up now is because it gives some indications of approaching that point. It doesn't have to do with being beautiful or divinely inspired. it has to do with the fact that without much fanfare a version of
LQG has, curiously enough, already been falsified. Synchrotron radiation from the Crab Nebula tested and shot down Smolin's Version A of LQG and it looks like Version B will be testable within maybe 4 years.

this is why, if you ever want to know about LQG, you should read
"Invitation to LQG" by smolin. It has almost no formulas--you can probably understand an important 20 or 25 percent of it. It has an FAQ written for
physicists from other fields. And most importantly it describes the
near term experimental situation

this paper is dynamite and it is the one of the very few papers I can imagine wanting to read with you or anyone at PF at this moment
...

from here: https://www.physicsforums.com/showthread.php?p=3023815#post3023815"

 

[marcus]

Marcus is promoting an idea that some papers on the theory of angular momentum, computing 12j and 15j symbols, constitute research on LQG :rofl: . Any well informed person realizes how ridiculous that is but it does not matter.
...

Here is the post that you are referring to:
https://www.physicsforums.com/showthread.php?p=3262991#post3262991

I don't have to "promote" that idea, since it is obvious. One of the authors already has a LQG paper out. Two of the authors have spent time at Marseille with Rovelli's group. Two of the authors will be attending Loops 2011 next month. Several of the papers contain extensive references to LQG research and discuss their relevance to the Loop program.

The fact is that the Wigner 15j is key to 4d spinfoam LQG, just as the 6j was key to Ponzano-Regge 3d gravity. Understanding the asymptotics of the 15j is critical for establishing the large-scale limit of LQG. Large scale means large j---so one needs to understand the limit of the 15j symbol for large j.

The papers in question are explicitly connected with LQG, and as I said, two of the authors will be at this year's Loops conference. So I really don't have to explain why you are wrong. You just need to consult the facts.

 

[atyy]

marcus, as you know, I disagree with your definitions. But I want to find out how strict they are. Let's say LQG goes in the direction of AdS/LQG, would you count that as LQG or not?

 

[smoit]

The fact is that the Wigner 15j is key to 4d spinfoam LQG, just as the 6j was key to Ponzano-Regge 3d gravity. Understanding the asymptotics of the 15j is critical for establishing the large-scale limit of LQG. Large scale means large j---so one needs to understand the limit of the 15j symbol for large j. ...

...
Is this Loop? You know from review papers that Loop draws heavily on several of the types of mathematics mentioned by the DESY librarians as keywords. But that does not make the paper Loop. I have to use an automatic criterion in order to tabulate changes---so I do not try to second-guess the DESY, I just go by what keywords they tag on the paper. They don';t say "quantum gravity, loop space" or "quantum cosmology, loop space" or "spin, foam" so I don't count it.

So, let's try your favorite approach on some of the allegedly LQG papers from Berkeley:

http://www-spires.fnal.gov/spires/find/hep/wwwtopics?key=9038191"
List of keywords assigned to the paper: Semiclassical Analysis of the Wigner $12J$-Symbol with One Small Angular Momentum: Part I

invariance, gauge
quantum mechanics
angular momentum
semiclassical
WKB approximation
invariance, gauge

http://www-spires.fnal.gov/spires/find/hep/wwwtopics?key=9030654"
List of keywords assigned to the paper: Semiclassical Analysis of the Wigner $9J$-Symbol with Small and Large Angular Momenta

invariance, gauge
phase, geometrical
angular momentum
factorization
semiclassical
rotation
spinorhttp://www-spires.fnal.gov/spires/find/hep/wwwtopics?key=8787883"
List of keywords assigned to the paper: Semiclassical Mechanics of the Wigner $6j$-Symbol

phase space, reduced
spin, network
semiclassical
mechanics
higher-dimensional
WKB approximation
angular momentum
Poisson bracket
integrability
symplectic

So, are these papers LQG or not, Marcus?

 

[smoit]

Several of the papers contain extensive references to LQG research and discuss their relevance to the Loop program. ...

According to your logic, any mathematician working on Calabi-Yau manifolds, G2 manifolds and related things, who may have attended some string conference should be classified as a string theorist, right?

 

[marcus]

Post#91 strikes me as irrelevant---argument for argument's sake. Smoit misrepresents what I have said, it's called "straw man" I use an automatic criterion to get paper counts so as to have an easy way to keep approximate track of changes.

Keeping track of developments at UC Berkeley physics department is a completely separate activity. I don't use keywordsearch statistics. I did not claim that Liang Yu papers were LQG! Nor would I have imagined adding them to a count of 2011 Loop papers. I let DESY librarians to the classification so there is some hope of consistency and changes in the numbers over time meaning something.

The situation with UC Berkeley is exactly as I have said.
UCB faculty and PhD students have either been visitors at Rovelli's LQG group on several occasions for extended periods or will attend the main Loop conference this year, or both, and collaboration with Rovelli's group has been possible. One of Littlejohn's PhD students is doing a Loop thesis and has already posted an explicitly Loop paper which I expect will be accepted for publication.

I have not said that Liang Yu's papers are specifically Loop. However all that work towards analytical understanding of the 15j symbol is enormously important to the Loop program and although Liang Yu himself may not be part of that program, he is in Littlejohn's group. And Littlejohn has at least one student doing a Loop thesis. So one has to see this as part of a pattern, in context. So that should certainly be pointed out!

The overall picture is that Berkeley is on the Loop map. That much is clear

So, let's try your favorite approach on some of the allegedly LQG papers from Berkeley:

...
...

http://www-spires.fnal.gov/spires/find/hep/wwwtopics?key=8787883"
List of keywords assigned to the paper: Semiclassical Mechanics of the Wigner $6j$-Symbol

phase space, reduced
spin, network
semiclassical
mechanics
higher-dimensional
WKB approximation
angular momentum
Poisson bracket
integrability
symplectic
So, are these papers LQG or not, Marcus?

:zzz:

I had an earlier discussion with Atyy about this. When all you are interested in is the SLOPE, basically. When you don't care about the gross amount but you want to see if something is increasing and how steeply or has leveled off, or is declining, then the convenient thing is to have some automatic yearly tally generated the same way year after year. I don't WANT my subjective judgment involved because that might influence things. So you pick some keywords and use them year after year----let DESY do the work and don't mess with it.
Here's my post to Atyy
==quote from me, page 2 of this thread==

Originally Posted by atyy
Tell me whether these papers are stringy or not:
http://arxiv.org/abs/hep-th/0501052
http://arxiv.org/abs/1010.5009

Is this an LQG paper or not:
http://arxiv.org/abs/math/0201177
​

I will do what you say, since you ask. I have not been counting "stringy" papers because the idea is too vague to make a well-defined time series. I set up a criterion "core String" depending only on the DESY library's cataloguing, so I could measure the same thing the same way year after year without and notice changes.

You mention Loop! But we are not playing some game of "string versus loop" here. It's boring when I point out something good happening in Loop and somebody immediately gets defensive and thinks they have to tell me why String is good (to keep them "even" I guess.) And if I see that the String program has a problem (which various people have attributed to various "wrong turns" and I find interesting) that is not intended as a game of competing theories, which one is "better".

I want to see as fairly and accurately how things are, not play "one-up".

People are always trying to make it seem that the two theories are "even", to balance the points. But they are not on a level. They are actually in very different circumstances as regards speed of development towards a finished formulation and testabilty and probably other things. Also the leadership style is noticeably different. And one has only about 200 active researchers who basically all know each other. And they have very different program goals.

So it seems ridiculous to try to equate the two on merits and demerits, or even spend much time comparing.

What I want to do in this thread is study the loss of expert interest in the String unification program. And hope to hear more about what the causes might be. If it has to do primarily with program management and vision then we might see a turnaround if the causes can be identified and remedied.

=================
about the papers. Here are their DESY keywords. When trying to track an index over time the thing is not to insert one's own judgment and most importantly, measure the same thing each time. So I count "core String" papers to be those the DESY librarians tag with keywords 'string model' or 'membrane model' The following two are not "core String" in that sense.:

...

The paper by Justin Roberts you mentioned is classified mathematics, not physics, and is not in Spires, so it has no keywords. Spires is basically HEP, not math. However Spires does have one paper, from the year before, by Justin Roberts!

http://www-library.desy.de/cgi-bin/spiface/find/hep/wwwtopics?key=4817060
Rozansky-Witten theory
field theory, topological
differential forms, symplectic
algebra, Lie
category
knot theory
mathematical methods

Is this Loop? You know from review papers that Loop draws heavily on several of the types of mathematics mentioned by the DESY librarians as keywords. But that does not make the paper Loop. I have to use an automatic criterion in order to tabulate changes---so I do not try to second-guess the DESY, I just go by what keywords they tag on the paper. They don';t say "quantum gravity, loop space" or "quantum cosmology, loop space" or "spin, foam" so I don't count it.
=====endquote=======

 

[mitchell porter]

String experts have decided after several decades experience that one should NOT think in terms of strings and branes in a geometry with compactified extra dimensions.

But what you get from AdS/CFT are low-dimensional field theories in flat space being equivalent to an AdS space times a compact space, containing strings and branes. The radial AdS dimension encodes the RG flow, and the compact space (and the objects with extension in it) is "made from" the space of ground states of the field theory. From this perspective, string theory is the universal theory of emergent RG geometry in quantum field theory. At the moment, it only works properly for an emergent AdS space, but if the dS/CFT correspondence can be understood, then this will be true for spaces of positive curvature as well. (In dS/CFT the boundary is purely spacelike and lies in the infinite past and future, rather than being timelike as in AdS/CFT, so it's as if the timelike direction in the Lorentzian gravitational space is emerging from Euclidean field theory on a sphere in the infinite past.)

So not only are people still doing flat-space string phenomenology, complete with branes and extra dimensions, but branes and extra dimensions have proved to be implicit in standard quantum field theory, where they emerge from the existence of a continuous degeneracy of ground states. That multidimensional moduli space of ground states is where the extra dimensions come from, in this case! Branes are domain walls separating regions in different ground states, strings are lines of flux connecting these domain walls. Furthermore, in gauge theories with a small number of colors, it looks like the extra dimensions will be a noncommutative geometry, it's only in the "large N" limit of many colors that you get ordinary space. (Consider that the noncommutative standard model of Connes et al is a theory of gravity on an "almost commutative" space - product of a Riemannian space and a finite noncommutative geometry - with the gauge bosons coming from gravity on the noncommutative part of the product geometry. This seems to be consistent with the picture coming from string theory.)

 

[smoit]

Reposting specifically for you, Marcus.

Marcus, I've tried to explain to you before that these keyword search statistics are extremely bad science. Besides not taking into account many statistical concepts such as sample size, it is not even clear that keywords are an effective substitute for just looking at the papers and recognizing what they are about. If you want to do statistics in a way that any scientist can respect, you must actually understand the properties of the sample, have some quantity in mind that is supposed to be of statistical significance, and then actually attempt to quantify the degree of correlation of your hypothesis with the sample. Absence of any of these results in a garbage in-garbage out situation.

To see how far off the mark your keyword searches were, I actually looked at all Witten papers for the periods > 2002- < 2007 and > 2006 - < 2011. These were obtained by using your date ranges in inspire, without the keywords. There is some overlap between the two periods, possibly because papers that appeared in the arxiv in 2006 also appeared in journals in 2007. Statistically, the overlap is not of much significance.

I attempted to classify papers which were string-related and those which were not. Basically my criteria were:

String: About strings, branes or 2d topological qft. Also includes AdS/CFT, the initial twistor amplitude paper and any Langlands papers that refer directly to 2d mirror symmetry.

Other: Papers about straight qft including particle physics, Chern-Simons and exotic qfts that don't directly imply string relations in their abstract or title. Also includes papers about pure 3d quantum gravity.

Results are:

2003-2006 http://inspirebeta.net/search?ln=en...+2002+AND+DATE+<+2007&f=&action_search=Search

-52 total papers

-15 conference proceedings
* 8 QFT
* 7 string

-37 journal articles
* 15 QFT
* 3 QG
* 19 string2007-2010 http://inspirebeta.net/search?ln=en...n_search=Search&sf=&so=d&rm=&rg=25&sc=0&of=hb

-25 total papers

-5 conference proceedings
* 5 QFT

-20 journal articles
* 9 QFT
* 2 QG
* 9 stringThe first thing to notice is that Witten's total output in 2007-2010 was half that for the 3 yrs prior. Measurements for this period will be less statistically significant as a result. As for relevant ratios,

2003-2006: 50% of total were string, 51% of journal articles were string
2007-2010: 36% of total were string, 45% of journal articles were string

It is amusing to do some statistics. Suppose that Witten's papers are randomly distributed between string and nonstring physics, and that the topics of papers are independent of previous papers. Then we have a binomial distribution. With 35 string papers in 77 trials, we have $$p=0.45$$. For the two periods we have

2003-2006: expected number of string papers: 52(0.45) = 24
variance: 52(0.45)(0.55) = 13
actual number of string papers: 26
expected: $$24\pm 3.6$$

2007-2010: expected number of string papers: 25(0.45) = 11
variance: 25(0.45)(0.55) = 6
actual number of string papers: 9
expected: $$11\pm 2.4$$

In both cases the number of string papers produced is within one standard deviation of the expected result. There is no reason to conclude that Witten has lost interest in string theory between these two periods.

You are free to conduct a similar analysis over a larger data sample, or for other notable string theorists. The results might be interesting. Keyword search results with no analysis will not be.

When you do a careful and proper statistical analysis you'll see that there is no decline of interest, as fzero has already confirmed. This is the point that YOU are deliberately ignoring. In particular, in your estimates you are completely ignoring the decline in the total number of papers put out by the same author in a given time period. It is completely natural for older professors to be less active and put out fewer papers. For instance, Eva Silverstein is from the younger generation and is still rather active, hence her absolute number of all papers, includings those on string theory, has not at all declined.

 

[marcus]

marcus, as you know, I disagree with your definitions. But I want to find out how strict they are. Let's say LQG goes in the direction of AdS/LQG, would you count that as LQG or not?

For one thing, Atyy, that's too speculative.

Another thing is we have to make a clear distinction between what gets tabulated to indicated changes, as a convenient index, versus one's own subjective casebycase assessment.

For a handy index to watch I let DESY do the work. I'm only interested in changes not absolute numbers, I want a rough idea. Maybe they overcount, maybe they undercount, but as long as they are reasonably consistent over time, their tally will PARALLEL the real world, roughly at least. So it is a convenient objective thing to refer to.

But in my own subjective mind there is no such thing as Loop apart from the self-selecting elite community of scientists. Same way with Mathematics. It has no verbal formula defining what is and what is not. No dictionary definition. No "essence". The content of Mathematics changes historically. It is what Mathematicians do.

Mathematicians are clearly identified for us by institutions. What is interesting deep valuable etc is determined by the self-selecting elite community, an aristocracy so to speak. Therefore it is capable of evolving. The field and the community co-evolve

In a lesser way perhaps, types of physics are like that. What Loop is is determined by things like the Zakopane school, and whose PhDs get postdocs where, and whose postdocs get jobs. And the lineup of invited speakers at Loops 2011, and what they talk about.

There is no "eternal essence".

Let's not waste time on "metaphysics". We know who the leaders are in LQG, if I saw them doing "AdS/LQG" whatever that means then I'd probably say yes that is included in Loop gravity. And our idea of who the leaders are, the central figures, evolves with time.
Now it's Ashtekar Rovelli Freidel Lewandowski...But in 10 years from now who can say? Could it contain Krajewski? Or Livine or Speziale or Bianchi or Dittrich or Ryan? just to name a few that happen to come randomly to mind. The trendsetter and field-changers will emerge, we will recognize them, we will see what they do. This will define the field. The field will evolve.
============================

With String the field seems to be in a crisis. Citations have fallen off sharply. Many fewer recent string papers make the top-cited list now than say in 2003. The field is in flux but there seems to be no clear direction. I'm really in suspense about where String is going.

Right now I'm thinking that this crisis of direction goes back to 2003 with KKLT, the 10^{too many} vacuums, and Susskind's panicky response. KKLT was a FAILED attempt to address the positive cosmological constant. And Susskind spooked people and they stampeded into the Multiverse. The leadership squelched Multivism in 2008, but it did a lot of damage and continues to. Recently here a highly respected Pro has said "We should not consider the Landscape to be a disaster". Translated, this means "Don't panic." I would say Landscape may indeed be a disaster, but one should remain calm in such a case and try to carry on business as usual. Panic only makes things worse.

 

[atyy]

Let's not waste time on "metaphysics". We know who the leaders are in LQG, if I saw them doing "AdS/LQG" whatever that means then I'd probably say yes that is included in Loop gravity.

OK, you said it.

 

[marcus]

You've got me curious now. Do you have anything particular in mind for AdS/LQG? Any research paper? Freidel wrote something about AdS/CFT correspondence a while back: 2008? But I would not call that AdS/LQG, not in a serious moment anyway.

==========EDIT===========
Atyy, you seem to have issues with DESY classification. I am flexible in individual cases, see connections, try to operate and discuss in good faith, and so forth. But to generate tables like this with Spires I simply pick the best available keywords and pay attention to the changes (not the absolute numbers). I do the same thing willynilly with LQG tabulations. This I think is what you consider "inflexible" and take issue with. So please tell me what your interpretation of this is! It's pretty stark so it has to mean something. If you don't think it reflects a change in the research focus/activity of these top people, then what? The classifiers used were "string model" and "membrane model"---BTW can you find another two or three DESY tags that you prefer, that you would propose running for comparison?

          1995-1998      1999-2002      2003-2006      2007-2010

Strominger     23             14             22              4
Maldacena      27             33             24              9 
Polchinski     21             17             11              4
Harvey,J       16             15              9              2
Duff,M         24             17              8              5
Gibbons,G      17             29             11              2
Dijkgraaf      18             11              9              7
Ooguri         31             18             13              8
Silverstein,E  16             15             16             10
Seiberg,N      19             16             22              1

PS: There were loud objections to having Witten on the list. So I have removed his name. We now have a sample of 10 top people. What are these people working on NOW? What is the String program about if you deemphasize basic parts of the paradigm, like brane and string (and compactified extraD)? If you want the Spires links, go back to post #63.

 

[atyy]

You've got me curious now. Do you have anything particular in mind for AdS/LQG? Any research paper? Freidel wrote something about AdS/CFT correspondence a while back: 2008? But I would not call that AdS/LQG, not in a serious moment anyway.

My point was that if you are so flexible with "LQG", then being similarly flexible with "string" will show that interest in string has not declined.

AdS/LQG doesn't really exist yet, but I am watching to see if it develops from

1) http://arxiv.org/abs/0907.2994 which links tensor networks and LQG

2) http://arxiv.org/abs/0905.1317, a speculative attempt to link tensor networks and AdS/CFT that has been cited by Vidal http://www.emergentgravity.org/drupal/sites/default/files/EGIV_presentations/Vidal.pdf and Evenbly http://pirsa.org/index.php?p=speaker&name=Glen_Evenbly in their talks and by http://arxiv.org/abs/1102.5524

3) http://arxiv.org/abs/1103.6264 which summarizes the known links between spin foams, lattice gauge theory and tensor networks

I know spin foams try to be more background independent than AdS/CFT, but if they work, I'd expect them to contain (or at least overlap) it a special case. I doubt it's a coincidence that Smolin (the LQG heretic who loves string), Freidel (who with Livine, Oriti, and Ryan represent a branch of LQG has often tried to interpret the formalism in "emergent" ways), Vidal, and Cachazo are all somewhere in Canada.

 

[marcus]

Atyy,
You seem to be taking issue with DESY cataloguing. What impresses me is the huge decline during the period 2003-2005, among a sample of top people. It would be interesting to know what other areas (whether or not you want to say they are "really" String) those people went into. Someone was claiming that the Langland's program was "really" String and "should" be counted. This is questionable. But that was just in the case of one person out of 10 or so. They pretty much all showed the same abrupt drop. So far not adequately explained away.

Still, if the DESY classification bothers you, here is a measure of declining interest that is not based on DESY. In making the following counts I tried to be inclusive in deciding what was string. I don't recall anyone pointing out a paper I missed: i.e. one not counted which they think is "really" a string paper. Make your own counts, if you want, and see if your numbers agree with mine.

Cites to recent String papers reflect the researchers' assessment of the value of their own colleagues' current output.
Spires top cited articles during odd years 2001-2009
(with number of recent string papers making the top fifty shown in parenthesis)

http://www.slac.stanford.edu/spires/topcites/2001/annual.shtml (twelve)
http://www.slac.stanford.edu/spires/topcites/2003/annual.shtml (six)
http://www.slac.stanford.edu/spires/topcites/2005/annual.shtml (two)
http://www.slac.stanford.edu/spires/topcites/2007/annual.shtml (one)
http://www.slac.stanford.edu/spires/topcites/2009/annual.shtml (one)

A paper is counted as recent here if it appeared in the past five years.
=========================

 

[atyy]

Atyy,
You seem to be taking issue with DESY cataloguing. What impresses me is the huge decline during the period 2003-2005, among a sample of top people. It would be interesting to know what other areas (whether or not you want to say they are "really" String) those people went into. Someone was claiming that the Langland's program was "really" String and "should" be counted. This is questionable. But that was just in the case of one person out of 10 or so. They pretty much all showed the same abrupt drop. So far not adequately explained away.

Still, if the DESY classification bothers you, here is a measure of declining interest that is not based on DESY. In making these counts I tried to be inclusive in deciding what was string. I don't recall anyone pointing out a paper I missed: i.e. one not counted which they think is "really" a string paper. Make your own counts, if you want, and see if your numbers agree with mine.

Cites to recent String papers reflect the researchers' assessment of the value of their own colleagues' current output.
Spires top cited articles during odd years 2001-2009
(with number of recent string papers making the top fifty shown in parenthesis)

http://www.slac.stanford.edu/spires/topcites/2001/annual.shtml (twelve)
http://www.slac.stanford.edu/spires/topcites/2003/annual.shtml (six)
http://www.slac.stanford.edu/spires/topcites/2005/annual.shtml (two)
http://www.slac.stanford.edu/spires/topcites/2007/annual.shtml (one)
http://www.slac.stanford.edu/spires/topcites/2009/annual.shtml (one)

A paper is counted as recent here if it appeared in the past five years.
=========================

Maldacena's paper was cited 392 times in 2001, and 696 times in 2009, clearly showing a decline in interest in string?

 

[mitchell porter]

AdS/LQG

Last month, MTd2 said something about https://www.physicsforums.com/showthread.php?t=484836#6". My intuition says that's another possible starting point for "AdS/LQG". The reason is just that braids mean something in (2+1) dimensions, and ABJM is the prototypical d=3 theory with an AdS4 dual.

edit: Also, a while back I https://www.physicsforums.com/showthread.php?p=3170483#8" if Marcolli's "topspin foams" might find a use in AdS/CFT.

 

[atyy]

Last month, MTd2 said something about https://www.physicsforums.com/showthread.php?t=484836#6". My intuition says that's another possible starting point for "AdS/LQG". The reason is just that braids mean something in (2+1) dimensions, and ABJM is the prototypical d=3 theory with an AdS4 dual.

Via Bilson-Thompson's ideas? That'd be sweet. I was thinking more conventionally, like using a supersymmetric spin foam to make a lattice version of ABJM.

 

[marcus]

Maldacena's paper was cited 392 times in 2001, and 696 times in 2009, clearly showing a decline in interest in string?

What I am tracking here is the value or quality of CURRENT STRING RESEARCH output.
I arbitrarily chose 5 years as the window. A paper of M from 1998 was recent in 2001 and no longer so in 2009.

I suppose one way to interpret---one way you could put it---is to say that there are a lot more string theorists now than in 2001, and their work is less significant, less interesting. They don't value each other's current research output as much as formerly was the case.

So the citation number crashed from 12 in 2001 down to 1 in 2009.
See post #100 of this thread.

BTW PAllen had some interesting reflections earlier on why this happened. I'll look back tomorrow and find his post.

I would say that there was a big decline in the interest/value of current String program research. And that is like a "leading indicator". It was followed in the next 3-5 years by many of the top people venturing out into more remote areas, with only partial or tenuous connection to program's homebase.

 

[smoit]

The numbers which Marcus is presenting here are completely meaningless. He measures people's interest in string-related papers by choosing his own phony criteria he calls "core string" and deliberately uses an absolute number of papers on a specific topic while failing to take into account the yearly change in the total number of papers output by the same author. fzero kindly went out of his way to explain to Marcus why his analysis was "garbage in => garbage out" and did a more careful job by doing some statistics on Witten's papers. As a result fzero finds no decline of interest, contrary to Marcus' allegation. Below I repost fzero's estimate.

Marcus, I've tried to explain to you before that these keyword search statistics are extremely bad science. Besides not taking into account many statistical concepts such as sample size, it is not even clear that keywords are an effective substitute for just looking at the papers and recognizing what they are about. If you want to do statistics in a way that any scientist can respect, you must actually understand the properties of the sample, have some quantity in mind that is supposed to be of statistical significance, and then actually attempt to quantify the degree of correlation of your hypothesis with the sample. Absence of any of these results in a garbage in-garbage out situation.

To see how far off the mark your keyword searches were, I actually looked at all Witten papers for the periods > 2002- < 2007 and > 2006 - < 2011. These were obtained by using your date ranges in inspire, without the keywords. There is some overlap between the two periods, possibly because papers that appeared in the arxiv in 2006 also appeared in journals in 2007. Statistically, the overlap is not of much significance.

I attempted to classify papers which were string-related and those which were not. Basically my criteria were:

String: About strings, branes or 2d topological qft. Also includes AdS/CFT, the initial twistor amplitude paper and any Langlands papers that refer directly to 2d mirror symmetry.

Other: Papers about straight qft including particle physics, Chern-Simons and exotic qfts that don't directly imply string relations in their abstract or title. Also includes papers about pure 3d quantum gravity.

Results are:

2003-2006 http://inspirebeta.net/search?ln=en...+2002+AND+DATE+<+2007&f=&action_search=Search

-52 total papers

-15 conference proceedings
* 8 QFT
* 7 string

-37 journal articles
* 15 QFT
* 3 QG
* 19 string


2007-2010 http://inspirebeta.net/search?ln=en...n_search=Search&sf=&so=d&rm=&rg=25&sc=0&of=hb

-25 total papers

-5 conference proceedings
* 5 QFT

-20 journal articles
* 9 QFT
* 2 QG
* 9 string


The first thing to notice is that Witten's total output in 2007-2010 was half that for the 3 yrs prior. Measurements for this period will be less statistically significant as a result. As for relevant ratios,

2003-2006: 50% of total were string, 51% of journal articles were string
2007-2010: 36% of total were string, 45% of journal articles were string

It is amusing to do some statistics. Suppose that Witten's papers are randomly distributed between string and nonstring physics, and that the topics of papers are independent of previous papers. Then we have a binomial distribution. With 35 string papers in 77 trials, we have $$p=0.45$$. For the two periods we have

2003-2006: expected number of string papers: 52(0.45) = 24
variance: 52(0.45)(0.55) = 13
actual number of string papers: 26
expected: $$24\pm 3.6$$

2007-2010: expected number of string papers: 25(0.45) = 11
variance: 25(0.45)(0.55) = 6
actual number of string papers: 9
expected: $$11\pm 2.4$$

In both cases the number of string papers produced is within one standard deviation of the expected result. There is no reason to conclude that Witten has lost interest in string theory between these two periods.

You are free to conduct a similar analysis over a larger data sample, or for other notable string theorists. The results might be interesting. Keyword search results with no analysis will not be.