Causes of loss of interest in String program

[marcus]

I'm not at all surprised that String researchers are slowly tranforming what they study into something more involved with cosmology, or as part of AdS/CFT. Even though something can be science even if it is untestable (we may be able to test it in the future), let's be honest - we don't want to forever be equation manipulators becoming ever more detached from the so-called experimental physics community. We want to see our ideas validated. It's no use being the world's greatest bus driver if you're driving in the wrong direction (and with regards to the String community, I have nothing but admiration for their bus driving skills, which in many cases are second to none).

Of course, my own views on this have been made plain in the past. We have to very careful that the ideas we put forward are themselves guided by physical intuition derived from experiment. Physics is an experimental science by definition. I say this as a theorist. I am under no illusions about the role of my work and I enjoy this subservience to observation and experiment. Science advances by incremental steps in theory and experiment with experiment leading the way, and physics is not exempt from this just because a large portion of the theoretical physics community imagine that the methods of Faraday, Maxwell and (early) Einstein are too primitive and old-fashioned to work.

Dax is back! I was really glad to see your post, Lieutenant. I'd like to invite you to take a look at the program of next week's "Mixed Quantum Geometry/Gravity" conference
https://www.physicsforums.com/showthread.php?p=3348219#post3348219
and would very much like to know your thoughts on it.

It is the first major international conference I know of that mixes presentations of Noncommutative field theory and NC Geometry with Supergravity with explicitly Stringy with Loop QG, and even Renate Loll's Triangulations QG and Martin Reuter's asymptotic safety QG research. I think it is something of a triumph to get representative people from all these different approaches into one hall to listen to each other. I hope they share ideas and problems---I hope it is actually productive. Maybe some postdocs will be enabled to jump fences.

The titles of all 30-odd talks are posted. Should give some idea of the character of the conference. ETH Zurich. Nice venue, except Zurich hotels seem very expensive.

 

[marcus]

A half-dozen more titles have been posted of talks to be given at the annual string conference. The conference starts in about two weeks. There are now 20 titles listed.


Niklas Beisert (AEI Potsdam) "Counterterms and E7 Symmetry in N=8 Supergravity"

Henriette Elvang (University of Michigan) review talk "Recent progress on amplitudes"

Rajesh Gopakumar (Harish-Chandra Research Institute, Allahabad) "Holographic Minimal Models"

David Gross (KITP, Santa Barbara) opening talk

Jeff Harvey (University of Chicago) summary talk

Thomas Klose (Uppsala University) "Recent Results for Holographic Three-Point Functions"

Andrei Linde (Stanford University) "Chaotic inflation in supergravity"

Marcos Mariño (University of Geneva) "Exact results and stringy effects in ABJM theory"

Liam McAllister (Cornell University) review talk "String cosmology"

Juan Maldacena (IAS, Princeton) "Comments on de Sitter perturbation theory"

Greg Moore (Rutgers University) review talk "The Recent Role of (2,0) Theories in Physical Mathematics"

Yaron Oz (Tel Aviv University) "Holography and Hydrodynamics"

Subir Sachdev (Harvard University) review talk "Quantum matter and gauge-gravity duality: quantum criticality, superconductivity, and Fermi surfaces"

Nathan Seiberg (IAS, Princeton) review talk "Recent advances in SUSY"

Ashoke Sen (Harish-Chandra Research Institute, Allahabad) "What can black holes tell us about microstates?"

Tadashi Takayanagi (IPMU, the University of Tokyo) "Holographic Entanglement Entropy and its New Developments"

Dimitrios Tsimpis (Université de Lyon) "Uses of 3d toric varieties"

Frank Wilczek (MIT) "Three Ways Beyond the Standard Model"

Edward Witten (IAS, Princeton) "Chern-Simons theory from four dimensions"

Fabio Zwirner (University of Padua) review talk "LHC results and prospects from a theorist's viewpoint"

======
Here is the link:
http://www-conference.slu.se/strings2011/programme_NEW.html

I have highlighted the Frank Wilczek talk because it stands out as the one talk apt to provide a challenging vision---alternative to the future lines of development assumed likely by the other speakers.

 

[marcus]

In the previous post I listed Strings 2011 invited talks and gave a link to the conference website. There does clearly seem to be a significant change in the climate of interest surrounding the string research program (however different people prefer to describe it) and this annual showcase conference provides an excellent window on what is happening.

I think it's an important development we should try to understand---and doing that is not in any way to "bash" string mathematics---a fascinating and ingenious analytical toolkit with potential applications in several areas.

What we should be trying to understand are the reasons for the striking changes going on around the string program. It has been suggested that comparatively few of the Uppsala talks explicitly involved string. The majority of them were basically about QFT. Verlinde's remarkable talk referred to string thought as "motivation" and "inspiration" for his attempt to find some "underlying" description.

Could it be that a significant number of string researchers are finding their way out of the field and back into QFT? Or, in Verlinde's case, into someplace entirely new? I sometimes hear work that does not directly involve string described as "string inspired" and "guided by insights from string theory".

Anyway the Uppsala conference is over and we can try to summarize what we've learned from the videos. I have some observations and hope others have some as well.

 

[marcus]

One of the most telling points came right at the start of this video of Chris Hull's talk
http://media.medfarm.uu.se/flvplayer/strings2011/video16

At lunch today one of the organizers was observing that my talk was unusual in being one of the few talks actually about string theory. It would be interesting to speculate on what that might mean about the state of the field, but it would be invidious to do so here.
​

Evidently this is a sensitive subject (potentially invidious to point out). String researchers have noticed that collectively their work involves less and less actual string theory proper, and some are worried enough by this so that it can be considered untactful to speculate about why that is happening.

As I said, it's obvious that one can generally draw some connection between whatever and something studied in the string program. So presumably one can usually say that this or that is "string inspired" or "guided by insights from string" if it makes people feel better. As for instance Verlinde tactfully did in the introduction to his talk. It's good for morale. But Chris Hull and the conference organizer he quoted were taking a harder look.

It's helpful, I think, to see that against these features of the background:

1. String jobs have fallen way off. First time faculty hires in Usa and Canada are essentially nil this year---not the case for particle theory as a whole.

2. Annual citations to recent string research have fallen--this reflects how useful/significant the researchers themselves find their own recent work.

3. Conference attendance is down. Registered participants at Strings 2011 numbered 257.

It may indeed be time for people to redefine their interests. Peter Woit had this comment:

One can make as much hype as one wants claiming that all good ideas in the hot topics of today (amplitudes, N=2 SUSY, various applications of gauge-gravity dualities, etc.) historically come from string theory, but the undeniable fact of the matter is that if you watch the talks at Strings 2011, virtually no one is talking about string theory itself or using string theory anymore to do anything. A student who wants to work on any of the hot topics has no reason to bother to learn string theory anymore.

What’s remarkable is that this seems to be true even in those areas where string theory has had some success, far away from the heavily promoted ones. Besides virtually no talks about string theory and unification, there’s also almost nothing about string theory as a theory of quantum gravity. The hot topic of recent years, the idea that string theory would explain heavy ion physics, seems to have completely disappeared.
​

http://www.math.columbia.edu/~woit/wordpress/?p=3811&cpage=1#comment-94426

 

[marcus]

Jeff Harvey, who had the important job of giving the summary talk at the end of the Strings 2011, compared string theory to the dead parrot in the Monty Python sketch, where the pet store clerk is trying to sell the customer a parrot is insisting that it isn't dead. He said string unification was not dead, it was "just sleeping" (quoting the M.P. pet store clerk.)
http://media.medfarm.uu.se/flvplayer/strings2011/video37
The specific reference to the Monty Python parrot, comes almost exactly 1/4 of the way along the timebar, where he starts talking about String as applied to Physics, as contrasted with mathematics.

Harvey acknowledged near the beginning (about 1/8 of the way along the timebar) that a lot of people at the conference had been asking "Where are the Strings?" He addressed that issue and put the best possible face on it, I thought. In fact, he said, many of the results presented at the conference could have been (or were) derived without any reference to strings, BUT many of those were inspired/motivated by IDEAS--or based on INSIGHTS--from string theory.
====================

I would urge people to also watch David Gross's opening talk (often the opening and summary talks give valuable perspective on the current state of the field in question). By comparison with Harvey, I thought Gross seemed more forlorn, apologetic, less upbeat. You might see what you think.
http://media.medfarm.uu.se/flvplayer/strings2011/video1

 

[atyy]

Did the parrot go to heaven or hell?

 

[marcus]

Atyy, you would have to go back and listen to Jeff Harvey's talk about the the current state of the field, and the conference papers. He reminded the audience of the salient details of the Monty Python skit.

As I recall John Cleese was the customer. It was clearly a stuffed parrot, and he was trying to make this clear to the salesman. "My good fellow, this...is...an ex-parrot!"

 

[JollyJoker]

The Monty Python sketch

http://www.youtube.com/watch?v=npjOSLCR2hE"

 

[atyy]

The Monty Python sketch

http://www.youtube.com/watch?v=npjOSLCR2hE"

Cool! String theory was right!

 

[marcus]

Cool! String theory was right!

Definitely! it is uncanny how it has proven to be so right all along
Post #274 on the previous page mentioned some reasons that could help to explain the change in the climate of interest surrounding the program.
https://www.physicsforums.com/showthread.php?p=3333598#post3333598 We should try to fill out the picture and put that together with the fact that at Strings 2011 the observation kept being made that the talks did not use string theory. This struck several people at the conference as odd. (Stringy thinking can well have contributed ideas, motivation, inspirations, insights but when it came right down to it the talk was about something else.) So it required comment.

Could this have something to do with the decline in string jobs? Drop in offers of first-time faculty positions, at least in Usa and Canada, possibly elsewhere? I will summarize some of the relevant numbers.

Annual first-time faculty hires (US and Canada) in HEP theory as a whole, and in string, averaged over 3 year periods

period                           1999-2001    2002-2004   2005-2007    2008-2010
annual HEP theory hires as a whole      18           24          23           13
annual string hires                      9            8           6            2

Registered participants in the annual conference (some years omitted for brevity)

Strings 2003 Kyoto     396
Strings 2005 Toronto   415
Strings 2007 Madrid    440
Strings 2009 Rome      450
Strings 2010 Texas A&M 193
Strings 2011 Uppsala   257

Number of recent string papers making the top fifty in the annual Spires HEP topcite list

year (some omitted for brev.)   2001    2003    2005    2007    2009    2010
recent work highly cited in year  12       6       2       1       1       0

Here a paper is counted as recent if it appeared in the previous five years. This gauges the quality/significance of current work by how other researchers in the field receive it.

Links to sources here
https://www.physicsforums.com/showthread.php?p=3373453#post3373453

=============================
Atyy, when Jeff Harvey referred to the dead parrot in the Monty Python sketch, he was specifically talking about STRING UNIFICATION, not about other areas of string research FWIW.
"This parrot is not dead, it's only resting."

It's quite possible that the program of string unification is "only resting"!
He suggested that it was only resting and that we might see a major advance, such as a solution to the Landscape Problem or something comparable to that, in the next few years.

 

[atyy]

Atyy, when Jeff Harvey referred to the dead parrot in the Monty Python sketch, he was specifically talking about STRING UNIFICATION, not about other areas of string research FWIW.
"This parrot is not dead, it's only resting."

It's quite possible that the program of string unification is "only resting"!
He suggested that it was only resting and that we might see a major advance, such as a solution to the Landscape Problem or something comparable to that, in the next few years.

Jeff Harvey is like the shop keeper.

I remember Moshe Rozali saying strings, as the focus of research, had died many years ago, and how he wished the general public knew about it.

 

[marcus]

Jeff Harvey is like the shop keeper.
...

I think when Jeff Harvey said "string unification" was just "resting" he did not mean string in any narrow sense. He meant all the stuff we usually associate with the term: superstring/M, dualities of different stringy theories in different numbers of dimensions, gravity/gauge duality.
It was pointed out that there was surprisingly little of any of that at Strings 2011.
A substantial number of the people, perhaps a majority, were back to doing Quantum Field Theory.

So this was commented on by people at the conference.

We are not talking about some perception of the general public, and how the experts know better, I'm sure you realize. We are talking about something that surprised the experts this year and so they were talking about it, asking "Where's the Strings?" Harvey, in his summary talk, had to respond somehow to that question because it was on a lot of the participants' minds. And he did, early on in his talk.

As I recall it was about 1/8 of the way thru---maybe earliest 10%, or 12%, of the timebar.

 

[atyy]

I think when Jeff Harvey said "string unification" was just "resting" he did not mean string in any narrow sense. He meant all the stuff we usually associate with the term: superstring/M, dualities of different stringy theories in different numbers of dimensions, gravity/gauge duality.
It was pointed out that there was surprisingly little of any of that at Strings 2011.
A substantial number of the people, perhaps a majority, were back to doing Quantum Field Theory.

So this was commented on by people at the conference.

We are not talking about some perception of the general public, and how the experts know better, I'm sure you realize. We are talking about something that surprised the experts this year and so they were talking about it, asking "Where's the Strings?" Harvey, in his summary talk, had to respond somehow to that question because it was on a lot of the participants' minds. And he did, early on in his talk.

As I recall it was about 1/8 of the way thru---maybe earliest 10%, or 12%, of the timebar.

But how can one's *literary sense* allow a resting parrot?

 

[marcus]

But how can one's *literary sense* allow a resting parrot?

That reminds me, the most adept talk in a *literary sense* (among all the Uppsala talks I've watched so far) was the one by Frank Wilczek.

He opened by saying he had been asked to talk about the state of physics and its possible future---and that he took that to mean particle physics and cosmology. Then looked around a bit diffidently and said that of course he may have been wrong to assume that.

Then he launched into discussion of standard model QUANTITATIVE UNIFICATION saying that what with LHC and the new cosmology observations expected in the next few years it was a good time to talk about these things. So he pointed to all the signs that there probably was some aesthetic improvement, say some SO(10) unification, out there to be had. By then, the talk was about 1/8 along the timebar, and he commented:

If you find yourself wondering "what does this all have to do with string theory"...well, you're asking a very good question.​

It was elegantly honest, double-edged and scalpel-sharp.

Wilczek bears watching. Depth. Literary finesse. Gentle disarming manner.

David Gross apologetic opening talk could be watched to provide a sense of contrast.

=======================
But more to the point of your question. Do parrots never sleep? And if a literary parrot is desired, shall we not sing a lullaby to one?

Rockabye Polly in the tree top.
Where the beams meet, the femtobarns rock.
Symmetry breaks and the Higgsy will fall,
And down will come...[etc etc]

[for reasons of meter, I considered "per femtobarn" as a synonym for "inverse femtobarn", which has too many syllables, as does "Higgs boson", to fit the line. Finally settled on simply "fb".]

 

[atyy]

So he pointed to all the signs that there probably was some aesthetic improvement, say some SO(10) unification, out there to be had. By then, the talk was about 1/8 along the timebar, and he commented:

If you find yourself wondering "what does this all have to do with string theory"...well, you're asking a very good question.​

I think it's moot whether string theory is dead. In the search for quantum gravity, it has achieved at least as much as Nordstrom gravity for relativistic gravity.

I think F-theory predicts not SO(10)? http://arxiv.org/abs/0904.3932 says "Nevertheless, it has been explicitly demonstrated that charged exotics cannot be completely removed by internal fluxes in SO(10) models and this likely extends to higher rank groups as well. While one can try to engineer models that utilize additional mechanisms to remove exotics, these difficulties seem to single out SU(5) models, where exotic-free spectra can be obtained"

 

[marcus]

I think it's moot whether string theory is dead. In the search for quantum gravity, it has achieved at least as much as Nordstrom gravity for relativistic gravity...

I agree, it is rather a moot point. And oh my yes! The program has achieved a vast lot in the 43 years during which string research has been conducted.

Wilczek was brought in by the Strings 2011 organizers specifically to talk about the future of physics beyond the standard model. More specifically particle physics and cosmology, or at least that is how he took his assignment.

 

[marcus]

Went back and listened carefully to make sure I got any possible quotes right.
http://media.medfarm.uu.se/flvplayer/strings2011/video24
==my attempt at transcribing Wilczek's talk==
I was asked to speak on my view of the current state--and future--of fundamental physics--I took that to mean high energy physics and cosmology...maybe that was an error here, but that's what I took...

I will start with a word of warning--that my perspective is very much a zero-brane perspective (that's b-r-a-n-e)--and, without further ado: three ways that I see we should be going beyond the standard model.

I will discuss quantitative unification, axions, and portals. [Actually he only covered the first two, had to skip over most of the third because of the time limit.]

The standard model is astoundingly successful, but it has major esthetic flaws:
Several moving parts, tenuously connected.

Many continuously adjustable parameters.

Some of these shortcomings may reflect pure "environmental accidents", others may reflect selection bias ("anthropic principle").​

In those conditions it might be diffcult to maintain the traditional high standards of theoretical physics. We might be reduced to accommodating facts as opposed to constructively explaining them. In particular in the case of attempting to determine those continuous parameters that appear in the standard model.

We can identify a few outstanding empirical facts, however, that seem unlikely to be explained away along those lines:

The gauge group and multiplet structure of the Standard Model, that practically beg us to construct a unified theory.

And then if we go ahead and do it, that it works quantitatively remarkably well.

(reference to the approximate unification of gauge couplings at high energy.)

There are small but nonzero masses of the neutrinos. Very small compared to the masses of the other particles. (That's a qualitative fact. None of these facts appear at any reasonable level to have anything to do with the existence of an intelligent observer. So these are things which, even in a Landscape picture, we would still be required to understand.)

And the last one is the smallness of the QCD theta parameter.​

There may be others, but these are the ones that will appear in this talk.

These facts have inspired truth-worthy theoretical proposals--with wide-ranging implications.

With the coming of the LHC, and expected advances in observational cosmology, the trial date for those ideas is approaching--which is what makes it appropriate to talk about it.
==that may be all of the talk I have time to transcribe right now==

 

[marcus]

Mitchell and Lieutenant Dax have both suggested reasons for the decline in interest. I don't see any others. If you see some please point them out!

Earlier, atyy seemed to be pushing for me to define what measures of interest to use in this thread. So I did specify some. Attendance at the annual Strings conference, for one. Annual citations to recent string research, for another. (Essentially how string theorists show their interest in their own colleagues recent work---I use a 5-year cutoff for recent.)
We could also include as measure the annual rate that (US+Canada) physics departments hire stringers as new faculty---the first-time faculty hires that the theoretical particle physics grapevine tracks. What I'm looking for are objective real-world measures.

They all point the same way. The question is WHY? What's the cause of the trend?

Dax had some constructive things to point out---cause-type things, explanations. And now I find that what she said is consistent with what several other people said at the recent Strings 2011 conference at Uppsala. So I'll quote Dax and we can read it thoughtfully.

I'm not at all surprised that String researchers are slowly tranforming what they study into something more involved with cosmology, or as part of AdS/CFT. Even though something can be science even if it is untestable (we may be able to test it in the future), let's be honest - we don't want to forever be equation manipulators becoming ever more detached from the so-called experimental physics community. We want to see our ideas validated. It's no use being the world's greatest bus driver if you're driving in the wrong direction (and with regards to the String community, I have nothing but admiration for their bus driving skills, which in many cases are second to none).

Of course, my own views on this have been made plain in the past. We have to very careful that the ideas we put forward are themselves guided by physical intuition derived from experiment. Physics is an experimental science by definition. I say this as a theorist. I am under no illusions about the role of my work and I enjoy this subservience to observation and experiment. Science advances by incremental steps in theory and experiment with experiment leading the way, and physics is not exempt from this just because a large portion of the theoretical physics community imagine that the methods of Faraday, Maxwell and (early) Einstein are too primitive and old-fashioned to work.

Strings 2011 as a conference was very much about theorists "slowly transforming what they study" as Dax said to something more timely and closer to the real world of LHC and observation cosmology.

One of the big themes at the conference was "Where's the strings?" Jeff Harvey made that the legend on one of his first slides in his summary talk at the conclusion of the conference. The prominent people invited to present talks at Uppsala are using actual string and brane and M-thinking less and less.

Dax pointed out something very simple: the incremental style of progress. And one of the most important talks at String 2011 echoed that. Wilczek's talk about "3 ways beyond the SM" was about how to make progress and the main ideas were incremental and timely. Wilczek proposed the criteria of plausible and accessible.
He presented two research thrusts: quantitative unification (threeway) and axion cosmology. And he said that now was a good time to talk about these things because they are now accessible---the ideas are now going to be put on trial.

The gentle message that Wilczek was presenting throughout his talk was that theorists should talk about what is timely---what is accessible.

By coincidence you can also see this idea in Dax second paragraph. And you can see it in prominent string theorist's behavior. They are percolating out of string/brane-centered research, and noticing that, and even, at the conference, asking about it.

Mitchell had something earlier to say about how this shift or percolation should be viewed.
I am still trying to integrate what he and Dax said, and what was said at the conference.

Here's the kind of thing we're trying to explain---find physics-based causes for---in this thread:

Annual first-time faculty hires (US and Canada) in HEP theory as a whole, and in string, averaged over 3 year periods, with prelim. estim. for 2011

period                   1999-2001    2002-2004   2005-2007    2008-2010    2011
annual HEP theory hires    18           24          23           13          11 
annual string hires         9            8           6            2           0

http://particle.physics.ucdavis.edu/rumor/doku.php

Several comments so far have been relevant to understanding this and related trends.

 

[mitchell porter]

Marcus, I guess you're referring to my remarks quoted in comment #261 (page 17 of this thread), about strings and branes perhaps being interpreted as abstract entities living in the "RG space" of a quantum field theory. I gave some problems for this perspective in comment #271. But just to recapitulate: this is essentially a question of how to interpret the appearance of a string theory in the holographic AdS bulk of a conformal field theory in flat space. You could take the attitude that the CFT, the boundary theory, is the real theory, and the string theory is a sort of auxiliary construct, an unphysical representation of composite states in the boundary theory, in a "space" (anti de Sitter) which is actually just a parametrization of energy scale and a few other properties of the boundary states. And certainly, in many of the applications of AdS/CFT, the AdS space is treated as just a helpful construct.

If you tried to take this perspective seriously, you might conclude that M-theory is the universal theory of a very large class of CFTs, when represented in this way. That in itself is a mysterious and interesting fact - why should M2-branes and M5-branes and the rest of the apparatus show up so naturally, in the expanded holographic interpretation of CFTs satisfying a few simple properties like http://arxiv.org/abs/0907.0151" ? The fact that CFTs also define a "skeleton" of the space of all possible QFTs (from the perspective of RG flow) only serves to underline the obscure intuition that M-theory here has a fundamental relationship to QFT in general.

But if we try to limit the significance of M-theory to being a master theory of RG flow for QFTs in flat space, we run up against the problem that string theory has been defined on backgrounds other than anti-de-Sitter! For most of the subject's history, string theory was studied on flat space backgrounds, and cosmological realism has led to the study of string theory in expanding space-times such as de Sitter space. The de Sitter example is interesting, because one version of "dS/CFT" would say that time is the extra holographic dimension here (as opposed to the extra radial dimension of space in AdS/CFT) - the CFT is a timeless Euclidean CFT which exists at past infinity, and the RG flow of that theory is the phenomenological time in which we perceive events as happening! That would also mean that time exists in the holographic bulk, where the strings and branes also live; with the further implication that if we regard our everyday space and time as physical, then we will have to regard the strings and branes as physical too, and the CFT as the peculiar asymptotic construct which lives at past infinity. Though I'm sure some people would convince themselves that they had found a way to tune into the timeless pre-holographic pre-big-bang reality... :-) Of course, this is all severe speculation, about the future of physics and about how it will be received, way beyond the present state of the art.

Coming down to earth, there's the more factual question of string theory's relationship to experiment, and how that will evolve in future. Well, string theory research clearly has a broad span that stretches from high theory and the mathematical study of strings in spaces quite unlike reality, to the numerous models that are produced by string phenomenologists. Dax's implication that string theorists are becoming "ever more detached" from experimental physics just isn't true, or else we wouldn't have new papers every month trying to realize the standard model, and extensions of it, in string theory. The new data from the LHC (i.e. the complete absence of anything beyond the standard model below 1 TeV, and the probable absence of the Higgs) is first of all going to roil the waters in ordinary field theory - there will be an attempt to establish which model should become the next standard model. This will certainly affect string phenomenology, in that people will now be trying to construct the "next standard model", and it won't just be one-way traffic either, since ideas about how to break supersymmetry are greatly informed by the available options in string theory.

Just as there is a spectrum of opinions in fundamental physics about what comes next, there's a spectrum of skepticisms - some are just skeptical about string theory, some are skeptical about supersymmetry, some about the Higgs and grand unification... some about relativity :-) ... etc. In certain respects, I think the interesting question for the immediate future will be attitudes towards supersymmetry, not string theory. If the LHC shows nothing new, the skeptics who reject, not just string theory, but also SUSY and perhaps GUT, will become more vocal. We might get a few more surprising "apostates" among the "elders" of physics. A failure of the Higgs to show will in any case be bringing new theories into prominence, and a lot of people will be clamoring for attention.

I can't say anything reliable about how that will play out, but I pay attention to a few rather heterodox ideas myself, so I can at least describe my own thinking. First, I should say that the more I've learned, the more I've appreciated the logic of various "orthodox" positions. The Higgs performs a function, supersymmetry performs several functions, string theory provides a further unification and a UV completion. This hegemonic view of what's next was not arrived at arbitrarily. In any case, when I study something that's really from left field, like Marni Sheppeard's motivic twistorial octonionic extension of Bilson-Thompson's braids, I don't do it just because it's a radical alternative to the stringy status quo. Inevitably there is also some possibility of hybridization or reinterpretation of string at stake, too. If you look at the ingredients of Sheppeard's synthesis, twistors are already mainstream, motives are definitely coming up, only the octonions are a little fringy. (As for the braids, the idea that particles are "octopi in the spin foam" is definitely fringe, but you can have knotted Wilson loops in perfectly orthodox gauge theories, so there's a good chance that some of the mathematics will cross over.) It is entirely possible that completely mainstream string phenomenological models have a mathematical re-expression in terms of motivic, twistorial, octonion-valued loop observables! The conceptual revolutions internal to string theory are definitely not over; the http://arxiv.org/abs/hep-th/0111068" , in particular, remains thoroughly unexplained.

So I think one can reliably predict that the future of string theory includes further conceptual change ("M is for motive"), and changes in the focus of phenomenological work, as new experimental data arrives. The big practical question is, I believe, string cosmology, and this will decide whether the eternal inflationary landscape that, say, Susskind favors is the right way to approach vacuum selection, or whether some other approach (a set of disjoint AdS superselection sectors, corresponding to different boundary CFTs?) ends up dominating. The centrality of CFTs to QFT, and of strings to AdS/CFT duality, also guarantees that strings will remain part of physics so long as QFT remains part of physics.

 

[marcus]

Mitchell, thanks for so much thoughtful and hopeful comment. Each paragraph deserves a detailed answer and I hope we get some from other interested people.
Much of what you say links the continued individual subjective fascination of the subject to the diffusion and dissipation of its thrust---and the present tendency to blend in with other fields, fields not specifically stringy braney eMmy or even extraDeeful.
So, paradoxically, you are giving compelling reasons for our seeing a realworld loss of interest while morally and at a speculative level one's interest can be as strong as ever.
We can see the prospects for SUSY dwindle, and first-time faculty string hires drop off, and yet we know that string will always be with us, because of its intrinsic fascination and the fact that it is (as you explain) inextricably interwoven with ordinary 4D quantum field theory!

I find what you say here particularly compelling:

The centrality of CFTs to QFT, and of strings to AdS/CFT duality, also guarantees that strings will remain part of physics so long as QFT remains part of physics.​

Of course there are degrees of "remaining a part of", and degrees of "centrality." But for many people, even as they percolate out into more ordinary d=4 quantum field theory research, the string inspiration will remain alive in their hearts.

I hope everyone reads the comments at Woit's blog to his 25 July post:
"String theorists throw SUSY under the bus."
http://www.math.columbia.edu/~woit/wordpress/?p=3864
John Baez and Bee Hossenfelder both commented.

 

[marcus]

I am gradually coming to some conclusions about the dwindling of interest in the string (unification) program. I think it has to do with a SWING BACK TOWARDS INCREMENTALISM and timely advance in theory---away from grand visionary leaps. Dax struck this note. So did Frank Wilczek in his talk to Strings 2011 conference. He stressed how theory must progress in a timely manner, in step with what is observationally accessible.

The decline/shift in interest is certainly real, and begs some attempt to determine causes. I summarized it in a different thread, which you may consult if you want sources.

Significant developments at the professional level can be summarized by saying that faculty hires for string are way down. (First-time faculty hires in Usa+Canada at or near zero this year.)
See post #241 above.

The annual string conference attendance has fallen off, and at the last one few of the talks were actually about string/M---people were asking "where are the strings?" and speculating as to the significance of that.

Annual citations to recent string/M research papers are sharply down from their earlier (say 2001-2003) levels.

On an anecdotal, individual level one can see a tendency for prominent string researchers to get out of the field and into related or neighboring areas of research. Perhaps "string-inspired" but not actually dealing with string brane and space with extra rolled-up dimensions. String unification seems to have been side-tracked or put on hold, with more emphasis on finding applications of the math tools in other areas. One hears a more sophisticated view that the string pictures may not necessarily be how the world is but rather one analytical approach---convenient in some context but not essential or fundamental.

There has also been some shift in views on Supersymmetry recently. Since signs of SUSY have not been showing up at the CERN collider. Quotes from string theorists have been assembled in this blog post.
http://www.math.columbia.edu/~woit/wordpress/?p=3864
...

Also recalling some relevant stuff from this thread:

...Strings 2011 as a conference was very much about theorists "slowly transforming what they study" as Dax said to something more timely and closer to the real world of LHC and observation cosmology.

One of the big themes at the conference was "Where's the strings?" Jeff Harvey made that the legend on one of his first slides in his summary talk at the conclusion of the conference. The prominent people invited to present talks at Uppsala are using actual string and brane and M-thinking less and less.

Dax pointed out something very simple: the incremental style of progress. And one of the most important talks at String 2011 echoed that. Wilczek's talk about "3 ways beyond the SM" was about how to make progress and the main ideas were incremental and timely. Wilczek proposed the criteria of plausible and accessible.
He presented two research thrusts: quantitative unification (threeway) and axion cosmology. And he said that now was a good time to talk about these things because they are now accessible---the ideas are now going to be put on trial.

The gentle message that Wilczek was presenting throughout his talk was that theorists should talk about what is timely---what is accessible.

By coincidence you can also see this idea in Dax second paragraph. And you can see it in prominent string theorist's behavior. They are percolating out of string/brane-centered research, and noticing that, and even, at the conference, asking about it.
...
Here's the kind of thing we're trying to explain---find physics-based causes for---in this thread:

Annual first-time faculty hires (US and Canada) in HEP theory as a whole, and in string, averaged over 3 year periods, with prelim. estim. for 2011

period                   1999-2001    2002-2004   2005-2007    2008-2010    2011
annual HEP theory hires    18           24          23           13          11 
annual string hires         9            8           6            2           0

http://particle.physics.ucdavis.edu/rumor/doku.php
...

So what we are seeing could simply be due to a natural tendency of professional theorists not to get themselves dug into a fortified ideological position but to be willing to swing back to a more pragmatic incremental mode of progress---more in step with current observation.

What I'm seeing is that many of the theory pros are testing alternative waters, while the more diehard voices are coming from peripheral people (whose realworld jobs have not actually been in string theory proper.)

Again, want to call attention to the Woit post about throwing SUSY under the bus. Some of the quotes are revealing of a shift in attitudes.
http://www.math.columbia.edu/~woit/wordpress/?p=3864

Also want to re-iterate (for the N-th time) that I admire and respect string mathematics. I'm not a "string critic" in some cliché sense. I want to get an accurate picture of what is going on in physics theory, without distortion by sentimental loyalties and the like. As a body of mathematical theory it is great, and related to a lot of other good mathematics!

The road towards unification in fundamental physics however could be more gradual however and might for example involve
1. 3-way unification (as suggested by Wilczek's talk on quantitative 3-way unif.)
2. better models of cosmology, esp. the beginning of expansion
3. quantum treatment of the geometry of space time (related to step 2.)
4. placing part 1. on a new geometrical footing (as per step 3.)

 

[mitchell porter]

3-way unification (as suggested by Wilczek's talk on quantitative 3-way unif.)

Do you mean his remarks on bottom-tau-top unification? i.e. looking for models in which all three particles have the same mass at high energies?

 

[marcus]

I'm talking about the first 20 or 25 minutes of his talk. It was the first topic he covered, called "quantitative unification". Wasn't limited to one particular conjectured means to the end.

He gave many aspects, including several reasons that (3-way) unif. was plausible, timely, accessible to verification/experimental guidance.

Gave several reasons he thought SM was just asking for it. Who knows? maybe he's wrong! (Seems to lean on SUSY a bit much.) But right or wrong, it illustrates the concrete incremental direction theory seems to be swinging.

Here's the link to Wilczeks talk. Because of its context I think it is a landmark. I think it should be on everybody's watch list.
http://media.medfarm.uu.se/flvplayer/strings2011/video24

 

[marcus]

I should complete the "resting parrot" lullaby song in reply to Atyy's question.

The Monty Python sketch

http://www.youtube.com/watch?v=npjOSLCR2hE"

Jeff Harvey is like the shop keeper.

I remember Moshe Rozali saying strings, as the focus of research, had died many years ago, and how he wished the general public knew about it.

But how can one's *literary sense* allow a resting parrot?

... Do parrots never sleep? And if a literary parrot is desired, shall we not sing a lullaby to one?

Rockabye Polly in the tree top.
Where the beams meet, the femtobarns rock.
Susy will break and the Higgsy will fall,
And down will come string theory, Polly, and all!

 

[MTd2]

The main cause, right now: LHC.

 

[marcus]

In this thread we are talking about the causes of the current loss of interest in the String resarch program. Several longer-term causes have been brought up, that have caused some attrition over the course of the last decade, but probably, as MTd2 says,

The main cause, right now: LHC.

Rockabye Polly in the tree top.
Where the beams meet, the femtobarns rock.
Susy will break, the Higgsy will fall,
And down will come string theory, Polly, and all!

And then there is this:

Annual first-time faculty hires (US and Canada) in HEP theory as a whole, and in string, averaged over 3 year periods, with prelim. estim. for 2011

period                   1999-2001    2002-2004   2005-2007    2008-2010    2011
annual HEP theory hires    18           24          23           13          11 
annual string hires         9            8           6            2           0

http://particle.physics.ucdavis.edu/rumor/doku.php
http://www.physics.utoronto.ca/~poppitz/Jobs94-08
http://www.math.columbia.edu/~woit/wordpress/?p=3864
https://www.physicsforums.com/showthread.php?p=3373453#post3373453

 

[marcus]

It's interesting to speculate as to the reasons for the longterm decline of interest in String over the past 10 years (not that immediately associated with LHC startup).

The decline itself is clear from the available indices: there has been a downtrend in the rate of first-time faculty hires, starting around 2001.
This is visible both in terms of absolute numbers (from average about 9 per year down to around 1 per year) and also in terms of string hires as a fraction of total Particle Theory hires.

There has been a decline in annual citations to recent string research by the theorists themselves. And in the past couple of years String conference attendance has fallen off, though that may be just temporary.
Number of recent string papers making the top fifty in the annual Spires HEP topcite list

year (some omitted for brev.)   2001    2003    2005    2007    2009    2010
recent work highly cited in year  12         6         2         1         1        0

Here a paper is counted as recent if it appeared in the previous five years. This gauges the quality/significance of current work by how much other researchers in the field refer to it.
Links to sources here
https://www.physicsforums.com/showthread.php?p=3373453#post3373453

I think clues to the causes of this decline might be sought in the special issue of the journal Foundations edited by Gerard 't Hooft. He invited a reputable bunch of string and other theorists to contribute articles for a retrospective issue called Forty Years of String Theory.

It's also interesting to speculate about what developments might re-energize the program.

I'll try to bring this thread up to date with current links and information.

For one thing, the table in post #306 (which was as of early August 2011) can be updated.
This is first-time faculty hires, Usa and Canada, in HEP theory overall and the String portion of that.
The source is http://particle.physics.ucdavis.edu/rumor/doku.php
Annual hires smoothed by averaging over 3 years intervals.
A physicist at the U Toronto (Erich Poppitz) charts first time faculty hires in High Energy Physics Theory by year and keeps track of what fraction of these are in string, which fraction are in lattice field theory, and so on.
http://www.physics.utoronto.ca/~poppitz/Jobs94-08
His chart shows 11 HEP theory hires in 2011 of which one was string.
2011 was the first year (since the record started in 1994) when "lattice" hires exceeded "string".

period                 1999-2001    2002-2004   2005-2007    2008-2010    2011
annual HEP theory hires   18             24            23             13            11 
annual string hires           9              8              6               2              1

19 institutions have posted openings for 2012. Of those, 14 show "short lists" of people they're considering, the average list being 63/14 between 4 and 5 in length. In aggregate, the short lists now contain 32 distinct names.
Too early to say anything about possible hires.

A new webpage has been started that reports on postdoc fellowships in a broader category (gen. rel. and quantum cosmology) which includes quantum gravity. So, something to keep an eye on:
http://sites.google.com/site/grqcrumourmill/

 

[marcus]

One of the things I've been wondering about is the possibility that part of the decline of interest in String could be due NOT to any fault of the String program itself but instead to the emergence of interesting alternative approaches to quantum gravity.
Steven Weinberg used the phrase "Plan B". He gave an invited talk at the Strings conference of 2010 in which he focused on his recent Safety QG research which he explained to the string theorists as Plan B in case their approach didn't work out.

The thing is, some of these Plan B approaches have started being pursued more energetically in recent years and some have made considerable progress.
So String has shifted from being overwhelming favorite ("our one best hope") into rough parity with some other approaches.

You see that in the major conferences. In the parallel sessions of the triannual Marcel Grossmann 2012 there is rough parity between sessions concerned with Loop and with String. It wasn't always that way.
Also in the 2012 International Colloquium on Group Theoretical Methods in Physics (called "Group 29" because it's the 29th in the series) there is rough parity. The first year that Loop has been included, and making quite a strong showing.
Invited talks on Triangulations QG, Safe QG, and Horava QG are featured at MG this year.
You see nonstring QG emerging in importance at another major conference as well, the triannual GR conference (or GRG = general relativity and gravitation.) BTW I think there's a chance that in 2013 http://www.fuw.edu.pl/~lewand/Bid-GR20.pdf GR will be held in Warsaw.

You also see it at the level of first time faculty jobs. Jon Engle, Bianca Dittrich, Hanno Sahlmann, Kristina Giesel, Param Singh, Catherine Meusburger...new people and in some cases positions in new places. Nonstring QG becoming more visible. The situation may not actually be good but it looks better than it did a few years back.

So there could be less of the "string=only game in town" mentality, and that could be contributing to the declining string activity/interest that we see. In other words the crowding into string that we saw earlier was an abnormal situation, which has been easing off. In that sense the decline shouldn't be seen as evidence of any program fault or an occasion for criticism.

 

[arivero]

One of the things I've been wondering about is the possibility that part of the decline of interest in String could be due NOT to any fault of the String program itself but instead to the emergence of interesting alternative approaches to quantum gravity.

To substantiate this, you should compare the evolution or three different fields: string theory intrinsic, string theory for quantum gravity, and string theory for particle models.

 

[marcus]

==quote==
One of the things I've been wondering about is the possibility that part of the decline of interest in String could be due NOT to any fault of the String program itself but instead to the emergence of interesting alternative approaches to quantum gravity.
==endquote==
To substantiate this, you should compare the evolution or three different fields: string theory intrinsic, string theory for quantum gravity, and string theory for particle models.

Hi Arivero, nice to hear from you. You know a lot about the history of different branches of the String program, having watched (and occasionally participated) for over 20 years, if I remember correctly.

You could sketch how you see it--I'd be interested. From my viewpoint, I suspect that the decline may be due to the rise of interesting other things to work on MAINLY BECAUSE I CAN'T THINK OF ANYTHING WRONG with the String program that wasn't already recognized back in 2001, say. What else could it be? (besides human factors like simple exhaustion, progress stalling, stuff getting stale)?
==============

BTW you know how David Gross is always saying "something important is missing, we may need a new idea of space and time..."
What that says is that QG could be a crucial step towards unification. I think a lot of the young researchers realize this. One or more of the various QG gambits could turn out to be a key step towards it even though it does not have unification as final goal. So working on a new conception of space and time can be just as interesting and just as historically important as working directly on unification. Maybe more doable/testable as well.

So the decline we see could simply be relaxation from an artificially narrow focus (the "only game in town" mentality) especially in the Usa. For that to happen all you would need is appearance of other exciting (potentially historically signicant) things to work on.

My two cents, maybe you have a different historical perspective. I remember your mountain river flash flood image as you were recalling developments in the 1990s which you experienced directly.

 

[arivero]

Hi... I do not believe to be able to sketch anything, I was only curious about your statistics. But, well, when you say that

From my viewpoint, I suspect that the decline may be due to the rise of interesting other things to work on

I think you are right if you speak of other things as interesting as the ones they were working on. Here it helps to understand what "interesting" means: for a team of theoretical physicists, it means that it is unsolved and intriguing and that a contribution -if not a full solution- can be done in a short time interval with the tools available to the team. And then...

human factors like simple exhaustion

make the rest, as the lead people who contributed the problems (say, Witten) becomes exhausted.

MAINLY BECAUSE I CAN'T THINK OF ANYTHING WRONG with the String program that wasn't already recognized back in 2001, say. What else could it be?

Here tell you again, do you mean the "string program for quantum gravity" or the "string program for QFT Standard Model"? Consider it. I would not even tell that the former has failed: they have most of the expected properties of gravity, do they?. The later, on the other side, has been unable to reduce the number of free parameters of the standard model.

 

[marcus]

...I think you are right if you speak of other things as interesting as the ones they were working on. Here it helps to understand what "interesting" means: for a team of theoretical physicists, it means that it is unsolved and intriguing and that a contribution -if not a full solution- can be done in a short time interval with the tools available to the team. And then... make the rest, as the lead people who contributed the problems (say, Witten) becomes exhausted.

To illustrate with some numbers FWIW. If one just looks at stuff that the librarians classify as string, AdS/CFT, or M-theory (they use the keyword "membrane") then one sees a gradual decline. A substantial number of these people must be finding other interesting stuff to work on that, whatever it is, does not fall into those categories.

The same thing was noticed and pointed out by several people at last year's Strings conference.
STRING,MEMBRANE,AdS/CFT RESEARCH BY YEAR
(search terms "string model", "membrane model" and "AdS/CFT correspondence")

2006 http://inspirebeta.net/search?ln=en...2y=2006&sf=&so=a&rm=citation&rg=10&sc=0&of=hb (1029 found)
2007 http://inspirebeta.net/search?ln=en...2y=2007&sf=&so=a&rm=citation&rg=10&sc=0&of=hb (1050 found)
2008 http://inspirebeta.net/search?ln=en...2y=2008&sf=&so=a&rm=citation&rg=10&sc=0&of=hb (1128 found)
2009 http://inspirebeta.net/search?ln=en...2y=2009&sf=&so=a&rm=citation&rg=10&sc=0&of=hb (1133 found)
2010 http://inspirebeta.net/search?ln=en...2y=2010&sf=&so=a&rm=citation&rg=10&sc=0&of=hb (1044 found)
2011 http://inspirebeta.net/search?ln=en...2y=2011&sf=&so=a&rm=citation&rg=10&sc=0&of=hb (927 found)
2012 http://inspirehep.net/search?ln=en&...2y=2012&sf=&so=a&rm=citation&rg=10&sc=0&of=hb (646 annualized from 136 found)

http://www.calendardate.com/todays.htm 17 March = 77/366

So other non-string stuff has arisen. Other lines of investigation are attracting the researchers' attention. This could be the main reason for the decline (which is most noticeable in citations to current research and in the drop off of job offers to string theorists for firsttime faculty positions in Usa and Canada. Bright people seem to be going into other theory lines and people in other fields of theory are getting the job offers.

Here tell you again, do you mean the "string program for quantum gravity" or the "string program for QFT Standard Model"? Consider it. I would not even tell that the former has failed: they have most of the expected properties of gravity, do they?. The later, on the other side, has been unable to reduce the number of free parameters of the standard model.

I could be wrong, Arivero, but I mostly am talking about string as an approach to quantum gravity. It is THERE where the rival approaches have appeared and I think have attracted researcher attention.
I recall Nima Arkani-Hamed back in 2009 saying string not likely to tell us anything about particle theory but might tell us something about gravity. So he agrees with what you just said. Gravity (spacetime geometry) is the main arena of competition. It's both the strong point of string and also the focus of the newer rivals. I think it is widely recognized that we have to get a new representation of space and time--a quantum geometry--before other things can follow on from that.

Like any of the newer approaches to QG, string should be expected to provide the same amenities that they do: it should offer a mathematical representation of the universe's dynamic geometry, it should resolve the initial singularity, it should be testable by early universe observations, it should be non-perturbative background independent and so on...
I think the reason for the decline in activity is not that it has failed or that it is somehow flawed, but rather that some new efforts have appeared on the scene and attracted research attention. It's natural for researchers to spread out a bit and work on several alternative approaches. String's no longer "only game in town" for bright young theorists. Also the growth in Loop phenomenology...ideas for testing...probably has some effect on the direction people's interest is going.

Anyway I was thinking mainly of the quantum geometry side of string.

 

[marcus]

So anyway, non-string QG is in course of achieving parity in the various real-world measures. It is no discredit to string, just that it is no longer "only game in town", and one simply has to register the fact. Departments need to diversify, and the "top dog" mentality can be dispensed with.

This year the main international conference relating to general relativity and gravitation is the 13th triennial Marcel Grossmann meeting (Stockholm July). There is a kind of balance.
In the parallel session schedule, Loop has about as much time as string allotted to it.
http://www.icra.it/MG/mg13/parallel_sessions.htm
Session L is Loop, session P is string.

In the invited plenary talks, there is a rough balance with 3 non-string QG speakers (Ambjorn, Horava, Reuter). It simply reflects growing interest in non-string QG---it's becoming a fashionable line of research. The Loop-theorist Laurent Freidel gave a plenary talk at the last MG meeting, now it's the turn of 3 other approaches to be showcased: triangulation, Horava-type, and asymptotic safe QG.

A similar rough balance was struck in this year's biennial conference on Group Theoretical Methods in Physics. It looks like Loop and String get about equal emphasis. Four years ago that was unimaginable, Loop did not appear on the program at all.
http://www.nim.nankai.edu.cn/activites/conferences/hy20120820/pdf/1st-Announcement.pdf
Sessions 8 and 9 are Loop and the related GFT.

I think a "no-fault" viewpoint could be the best to take. Some people who formerly did string are moving over into new areas of research part or full time--presumably because those new areas appear interesting. This naturally translates into declining activity in the older area. But it doesn't mean the older approach was a mistake, and maybe it didn't need that many researchers working on it in the first place.

Does anyone disagree and want to argue for another interpretation? Can you propose a different explanation for the declines in citations and job offers noted here in post #307?
https://www.physicsforums.com/showthread.php?p=3813260#post3813260

 

[marcus]

The main cause, right now: LHC.

That indicates a different viewpoint from the simple "no-fault" explanation I was proposing.

LHC results have been running against String expectations and this could be dampening enthusiasm in the field, among some practitioners though certainly not all.

No evidence of supersymmetry so far, or extra dimensions. I think we would be seeing a far busier string scene now if some evidence of low energy supersymmetry had appeared (something many people spoke confidently of a few years back).

An interesting side aspect: there was a workshop on a line of string research called F-theory at Stonybrook's Simons Center for Geometry and Physics this past week March 19-23:
http://scgp.stonybrook.edu/archives/1493
Michael Dine was the main organizer. F-theory seems to have made a bunch of predictions which have not panned out, so you could say it has been refuted.
The Thursday morning session was on F-theory phenomenology and included a video recorded discussion with Dine, Moore, and Seiberg titled “A Critical Look at Phenomenological Issues in F-theory”
http://media.scgp.stonybrook.edu/video/video.php?f=20120322_1_qtp.mp4

Beginning shortly after minute 52:30 of this video discussion, Michael Dine sums up the situation (rather gloomily) as he sees it:
"A lot of us I think are resigned to the idea that maybe there’s supersymmetry and it’s going to look tuned, or maybe there’s not low energy supersymmetry. I think a challenge I’ve always said for string theory is to try and think about theories without supersymmetry and that has proven to be hard. But you know, that’s certainly a direction which maybe we’re being confronted with."

It may be that LHC results, as they accumulate, are tending to deflate the String program. That's not my take on it but I'd be interested to hear what others might have to say along the lines of what MTd2 said. In any case, that is mostly in the particle theory area, where as Arivero pointed out the String program has already been a disappointment:

Here tell you again, do you mean the "string program for quantum gravity" or the "string program for QFT Standard Model"? Consider it. I would not even tell that the former has failed: they have most of the expected properties of gravity, do they?. The latter, on the other side, has been unable to reduce the number of free parameters of the standard model.

I'm mainly interested in the various approaches to quantum geometry (QG). In that area, what I see is simply what I would call a return to normalcy, with non-string approaches gradually achieving parity. No direct connection with LHC there and more of a "no-fault" explanation.

 

[arivero]

I'm mainly interested in the various approaches to quantum geometry (QG). In that area, what I see is simply what I would call a return to normalcy, with non-string approaches gradually achieving parity. No direct connection with LHC there and more of a "no-fault" explanation.

Well, a return to normal would imply, what, about two or three papers every year ? Point is, which was the production and number of people involved in quantum gravity in the seventies? De Witt and some alike minds.

Asthekar lead a revolution in the field, but given that it was done at the time where string theory had attracted more people to think that the QG problem was approachable, it is not easy to assess what "normality" had been without the coexistence with string based arguments.

An interpretation of "parity" could be to argue that without particles nor GUTs probably a variant of the string had appeared anyway, because the Riemann tensor has dimensions of area, and really Riemann curvature is an average about different combinations of planes to cut space and measure local curvatures (people who is surprised that string theory produces gravity has not really thought a lot about Riemann tensor and the different n-dimensional generalizations of the concept of curvature). So some quantisation using world-surfaces had existed anyway, but surely with the same level of attention span that other approaches.


The LHC explanation applies only to the particle side, and in this case I believe it is really a case of attention span. The number of physicists is more or less constant, or at least slowly changing, and then a higher emphasis on LHC results will detract effort from other venues, even if they had similar quality.