Causes of loss of interest in String program

[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.

 

[MTd2]

If the LHC applies only to the particle side, what motivation is left to study strings (not counting xyz/CFT stuff) ? Anything else is just too convoluted and complicated.

 

[arivero]

If the LHC applies only to the particle side, what motivation is left to study strings (not counting xyz/CFT stuff) ? Anything else is just too convoluted and complicated.

Well, just from the definition, it seems clear that string theory is to riemannian geometry as homotopy is to topology, so it seems reasonable to have it in the basic toolbox. Plus, the fact that the worldsheet has the right units to match the Riemann tensor implies suggests that it is relevant to the Einstein Hilbert action.

for particles, we told of a "wrong turn" of string theory. For gravity, it is even worse, because gravity -metric, EH action, etc- has never been seriously a lead for the development of ST. But it is clearly a basic tool. Of course, same could be said of Connes Spectral Action.

 

[MTd2]

What you are saying is an aesthetic argument. You mention "imply", "suggest", but what really decides is the experimental evidence of this kind of thing, which is null up to now. People will at start to move on.

 

[arivero]

You mention "imply", "suggest", but what really decides is the experimental evidence of this kind of thing,

Well, for the gravity side of the string, the only contradictory experimental evidence is the dark energy, isn't it? I mean, the usual way for the string to produce 4D gravity was to have AdS kind of metric, which is not compatible with positive cosmological constant. And even here, this is related to vacuum energy, a problem that usually is contemplated also from the particle side.

In any case, note that my use of implies/suggests was in a phrase about mathematical relationships.

 

[marcus]

Well, just from the definition, it seems clear that string theory is to riemannian geometry as homotopy is to topology, so it seems reasonable to have it in the basic toolbox...
...a basic tool. Of course, same could be said of Connes Spectral Action.

In fact I gather that a substantial number of people do view it as a set of mathematical tools, not as a definite physical theory, having directly to do with nature.

It will be interesting to see how the Munich Strings 2012 conference shapes up. It impresses me so far as a serious well-intentioned effort to re-vitalize the field. The list of plenary speakers was posted today:
http://wwwth.mpp.mpg.de/members/strings/strings2012/strings_files/program/speakers.html

Opening, closing, and overview speakers names were posted at the site earlier, but here is the new list posted today:

M. Aganagic (UC, Berkeley)
F. Alday (Oxford University)
L. Anderson (Harvard University)
I. Antoniadis (CERN)
N. Arkani-Hamed (IAS, Princeton)
C. Bachas (*) (ENS, Paris)
F. Cachazo (Perimeter, Waterloo)
A. Castro (McGill, Montréal)
M. Cvetič (UPenn, Philadelphia)
T. Dimofte (IAS, Princeton)
B. Freivogel (*) (MIT, Cambridge)
M. Gaberdiel (ETH, Zürich)
D. Gaiotto (IAS, Princeton)
C. Gomez (Universidad de Madrid)
J. Heckman (IAS, Princeton)
G. Horowitz (UC, Santa Barbara)
N. Iqbal (KITP, Santa Barbara)
S. Kachru (Stanford University/SLAC)
Z. Komargodski (Weizmann Institute, Rehovot)
S. Kortner (MPI Physik, München)
J. Maldacena (IAS, Princeton)
H.P. Nilles (Universität Bonn)
A. Polyakov (Princeton University)
L. Rastelli (C.N. Yang Institute, Stony Brook)
N. Seiberg (IAS, Princeton)
E. Silverstein (Stanford University/SLAC)
A. Strominger (Harvard University)
E. Witten (IAS, Princeton)
M. Yamazaki (Princeton University)
B. Zwiebach (MIT, Cambridge)

(*) to be confirmed

Correct me if I'm mistaken, but I can't see anyone here likely to talk about the "anthropic string landscape" or "multiverse" statistics. Those sorts of talks were excluded from Strings 2008 and have normally not been featured at the annual Strings conference since then. To the extent that I can judge, it looks like a strong speakers list---as if the organizers are putting more into it compared with, say, 2010 and 2011.

 

[marcus]

Today the Strings 2012 conference organizers put the (still incomplete) list of talks online:
http://wwwth.mpp.mpg.de/members/strings/strings2012/strings_files/program/talks.html

By pleasant coincidence the first (only, so far) talk title listed illustrates the growing interest in non-string QG:
Hermann Nicolai Alternative approaches to quantum gravity: a brief survey
In a small way this tends to confirm the "no fault" explanation for the dwindling of activity/interest in string. It just means that nonstring QG has grown and begun attracting more research attention. There may also be other contributing causes (several people have suggested some earlier in this thread).

Since we're starting a new page I'll recall some of the basic information that we're considering how to explain.

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.

A physicist at the U Toronto (Erich Poppitz) charts first time faculty hires in High Energy Physics Theory (Usa and Canada) 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.

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

Annual hires smoothed by averaging over 3 years intervals.
The source is http://particle.physics.ucdavis.edu/rumor/doku.php
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/
Anyway the string share of first-time faculty hires used to be around 9/18 and is now more like 1/11.

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 currently refer to it.

I think clues to the causes of this decline might also 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.
http://en.wikipedia.org/wiki/Foundations_of_Physics
Some of the articles which 't Hooft invited to be in this special issue of the journal are available online:
http://arxiv.org/find/grp_physics/1...+co:+AND+string+AND+Forty+years/0/1/0/all/0/1

 

[negru]

I don't see where you got the "other games in town" theory. Almost none of the people previously working on string theory switched to any of the alternatives. Certainly not to LQG. A few to entropic gravity and Horava, but those only gave like a bunch of highly cited papers, and as far as I can tell both are dead now.

What's going on is that recently people have become more interested in various field theories, most dual to string theories. Doing field theory is the same as doing string theory. You can't expect to make any progress on M theory without understanding stuff like ABJM or (2,0) theory.

 

[MTd2]

Doing field theory is the same as doing string theory. You can't expect to make any progress on M theory without understanding stuff like ABJM or (2,0) theory.

This is so sad, it is funny. This is the reason why people are losing interest in the string program. It is a huge tower of knowledge that doesn't pay back at all with empirical evidence, except with, maybe, hope. And that is vanishing. People doesn't need to switch to other fields to contribute with the lost of interest in strings. They either move on or will die. The point it is that they will eventually not be replaced, significantly, by a good number of younger researchers.

There are vasts domains on research on other areas of knowledge, which are much easier to study and rewarding in so many aspects. Even, speculatively speaking, there is less and less empirical motivation, regardless of the reason given by string theorists, to keep on the string program and not to start going to other speculative fields of quantum gravity. They can come and go fast, but, in the end, the sum of wasted time is always going to infinity.

 

[negru]

And there is any empirical evidence to favor other speculative fields of quantum gravity?

 

[MTd2]

And there is any empirical evidence to favor other speculative fields of quantum gravity?

As I wrote above, there isn't. The sum of waste of time of all of them together goes to infinite, no matter the theory. The difference, though, it is that they are easier.

 

[negru]

Well that's hardly a good reason to change what you're working on. If string theory were easier a lot fewer people would be interested in working on it. People are usually happier knowing that what they're spending time on is making maximum use of their abilities.

Also string theory isn't difficult. I find all the technical and statistical details of high energy experimental talks more difficult than any topic of string theory. The problem is people for some reason are still hoping everyone can know and maybe even be good in everything. But we aren't living in the 1700s anymore. To be good in your field you need to specialize. I find the way physics is taught from high school up to including grad school incredibly outdated and inefficient. The material is almost the same as 100 years ago. Classical mechanics, EM, stat mech. Then there's some quantum thrown in at the end, and if you're doing qft you're already advanced.
The research I'm doing now everyone could've easily been doing in high school, with the proper guidance of course.

 

[MTd2]

People are usually happier knowing that what they're spending time on is making maximum use of their abilities.

That's a good thing when you are doing it for a constructive feedback. From medicine to art. People are usually not fond of sisyphean tasks. In the case of art, few people can stand being like van Gogh. Although, he was recognized after death...

And those hardly the same as 100 years ago. These things were barely developed back then. On string theory, you've got to fully use them, in the modern sense, for almost no reward. Or at least, in a must more broad sense than in other areas. It's much less specialized. On the contrary, even great advances on science and technology, nowadays, requires just very specialized application of those fields, as you say.

 

[Aidyan]

I could mention several technical reasons why SS theory leaves me cold, but am still a layman in QFT and don't dare to go into technical details I'm still learning. But from a simple historical perspective, I'm wondering if there is a single example in the history of physics where hundreds, if not thousands, of top physicists worked on for more than three decades without producing a concrete result, and then turned out to be a correct theory? I can't think of any. People are slowly realizing that if a theory, despite all the efforts, does not produce tangible results after say 15, max. 20 years, then it must be wrong. And I'm afraid that this holds for LQG too.

 

[MTd2]

Sure, there are examples of physical theories that fits that criteria. Aristotle's and Ptolemy's theories and biology were considered correct for almost 2 thousand years and several thousand, millions(?), people worked on them.

LQG just became more fashionable from 5 years to now. It was an obscure theory before. It is almost mainstream right now. But it is sort of non predictive too, that annoys me too.

AS gravity is an obscure research up to now, despite of being 35 years old. But it nailed Higg's value precisely! I am more interested in this one now, although one of the saddest possibilities with that is the existence of the large desert up to plank scale.

 

[arivero]

Hmm, MTd2, I think that you have misread Aidyan question. He asks for heavy involvement, no results during a long period, and then suddenly it happens to be right. I doubt you are claiming that Aristotle biology happened to be right at the end, nor even a huge involvement of resources (by biologists, aka veterinaries and doctors, not by teologists).

 

[Aidyan]

In fact. As everyone knows the aristotelian cosmogony turned out to be dead wrong (and no, between Ptolemy and Copernicus almost nobody was working on it). Would there have not been the church and its inquisition who dogmatically insisted to pursue that path we could perhaps have avoided the 'dark ages'. I hope really that string theoreticians will not take that as an historical reference case. This would only discredit them. And I don't want to wait another 2000 years ...

 

[MTd2]

Hmm, MTd2, I think that you have misread Aidyan question. He asks for heavy involvement, no results during a long period, and then suddenly it happens to be right. I doubt you are claiming that Aristotle biology happened to be right at the end, nor even a huge involvement of resources (by biologists, aka veterinaries and doctors, not by teologists).

Oh, yeah! I misread! I just noticed that!

 

[MTd2]

In fact. As everyone knows the aristotelian cosmogony turned out to be dead wrong (and no, between Ptolemy and Copernicus almost nobody was working on it).

No! Thousands of people indeed researched the Ptolomaic model! It indeed achieved a great accuracy during the Islamic period. In fact, the accuracy was so great, that the muslim astronomers came up first with the heliocentric model, or close to it:

"Ibn al-Shatir, the Damascene astronomer (1304–1375 AD) working at the Umayyad Mosque, wrote a major book entitled Kitab Nihayat al-Sul fi Tashih al-Usul (A Final Inquiry Concerning the Rectification of Planetary Theory) on a theory which departs largely from the Ptolemaic system known at that time. In his book, "Ibn al-Shatir, an Arab astronomer of the fourteenth century," E.S.Kennedy wrote "what is of most interest, however, is that Ibn al-Shatir's lunar theory, except for trivial differences in parameters, is identical with that of Copernicus (1473–1543 AD)." The discovery that the models of Ibn al-Shatir are mathematically identical to those of Copernicus suggests the possible transmission of these models to Europe.[14] At the Maragha and Samarkand observatories, the Earth's rotation was discussed by al-Tusi and Ali Qushji (b. 1403); the arguments and evidence they used resemble those used by Copernicus to support the Earth's motion.[15][16]"

http://en.wikipedia.org/wiki/Geocentric_model#Geocentrism_and_Islamic_astronomy

 

[negru]

I could mention several technical reasons why SS theory leaves me cold, but am still a layman in QFT and don't dare to go into technical details I'm still learning. But from a simple historical perspective, I'm wondering if there is a single example in the history of physics where hundreds, if not thousands, of top physicists worked on for more than three decades without producing a concrete result, and then turned out to be a correct theory? I can't think of any. People are slowly realizing that if a theory, despite all the efforts, does not produce tangible results after say 15, max. 20 years, then it must be wrong. And I'm afraid that this holds for LQG too.

The history of things is irrelevant here. String theory and its alternatives have a minimal amount of external data to work with. This was usually not the case before. People were observing various phenomena then trying to explain them. They were guided by data. Now we're not observing anything new, we're just trying to make the theory we have prettier. Any new predictions we could make will very likely be at unobservable energies anyway (unless we're extremely lucky and there is low energy susy, or dark matter detection says anything). So even if string theory somehow made a prediction around i don't know say 100-1000 Tev, no one would take it seriously anyway for another 50 years or so. Almost everyone working on string theory now would be dead by then.

 

[marcus]

In regards testability (mentioned above) some readers might be interested in:
http://arxiv.org/abs/1204.1288
Perturbations in loop quantum cosmology
Ivan Agullo, Abhay Ashtekar, William Nelson
(Submitted on 5 Apr 2012)
The era of precision cosmology has allowed us to accurately determine many important cosmological parameters, in particular via the CMB. Confronting Loop Quantum Cosmology with these observations provides us with a powerful test of the theory. For this to be possible we need a detailed understanding of the generation and evolution of inhomogeneous perturbations during the early, Quantum Gravity, phase of the universe. Here we describe how Loop Quantum Cosmology provides a completion of the inflationary paradigm, that is consistent with the observed power spectra of the CMB.
4 pages, ICGC (2011) Goa Conference proceedings

and in the earlier paper (cited 45 times), simply as an example:
http://inspirehep.net/record/812301?ln=en
Cosmological footprints of loop quantum gravity.
J. Grain (APC, Paris & Paris, Inst. Astrophys.), A. Barrau (LPSC, Grenoble & IHES, Bures-sur-Yvette).
Feb 2009
7 pp. Phys.Rev.Lett. 102 (2009) 081301

You shouldn't lump Loop in with String. Loop is just beginning to get broad attention from researchers, more-than-token representation at major conferences. Even the biennial Loops conference only goes back to 2005. Their arcs of historical development are quite different.
===============

As I mentioned before, 6 or 7 days ago the Munich organizers of Strings 2012 posted the list of 39 invited speakers, but the titles of the talks are all blank except for one. So it has been for nearly a week. The only talk, out of 39, whose title is listed is
Alternative approaches to quantum gravity: a brief survey
http://wwwth.mpp.mpg.de/members/strings/strings2012/strings_files/program/talks.html
It's hard not to conclude that leading string folks and likely participants are interested in hearing about and discussing this. And this, I think, is relativey new. I don't recall much attention to non-string QG, at past conferences.

I'm pointing out a subtle change in climate, or perhaps just a shift in the weather pattern.

 

[Aidyan]

No! Thousands of people indeed researched the Ptolomaic model! It indeed achieved a great accuracy during the Islamic period. In fact, the accuracy was so great, that the muslim astronomers came up first with the heliocentric model, or close to it...

MTd2, these are only isolated historical examples (and you surely can find more), but can not in the least be compared with the effort, the people, the machinery and the money spent today on string theory. In string theory there are hundreds of "Ibn al-Shatirs" who produce an amount of papers, books, articles and whatever documents in few month, perhaps even only few weeks, comparable to what humanity did in 20 centuries (just compare what pops into existence daily on arxiv...). Modern organized science in the form we know exists only since three max. four centuries. And since then I can't think of another theory in physics that was so revered, cherished and honored for a so long time without producing concrete results.

The history of things is irrelevant here. String theory and its alternatives have a minimal amount of external data to work with. This was usually not the case before. People were observing various phenomena then trying to explain them. They were guided by data. Now we're not observing anything new, we're just trying to make the theory we have prettier. Any new predictions we could make will very likely be at unobservable energies anyway (unless we're extremely lucky and there is low energy susy, or dark matter detection says anything). So even if string theory somehow made a prediction around i don't know say 100-1000 Tev, no one would take it seriously anyway for another 50 years or so. Almost everyone working on string theory now would be dead by then.

I wouldn't call QM, GR, the SM and all the modern particle physics and astrophysical observations "minimal amount of external data to work with". And what "data" had three guys as Copernicus, Kepler or Tycho Brahe to work with? Only those of the extremely limited human senses, and yet they produced something. The "unobservable energies" argument is acceptable provided that a research along the "unobservable energies" line will sooner or later lead to "observable energies" data. Or at least a minimal hint, an allusion, a scratch of evidence. History suggests that "sooner or later" means about a couple of decades, not centuries, and not to say millenniums.

 

[arivero]

Kepler

Hmm perhaps we could have a better example here, with the theory of indivisibles/fluxions... it is a whole lifespan of development, the initial players, such as Kepler or Cavalieri, never see the final physical results (Newtonian Dynamics). Kepler himself -whose treatise is mostly numerical- was never considered a player, except perhaps by Cavalieri, who insisted on showing his work to Galileo (and failing to attract attention). Cavalieri atoms run into all kinds of problems, until Newton and Leibnitz got the final formulation.

 

[negru]

I wouldn't call QM, GR, the SM and all the modern particle physics and astrophysical observations "minimal amount of external data to work with".

Of course not, but the relevant data was already used to give precisely QM, GR and the SM. if you want a bigger theory, you need more data than was already used, that was my point. Just like Newton used all the data he knew to get classical gravity. Even if he saw hints of things beyond classical gravity, the data he had wouldn't have been anywhere near of helping him.

And what "data" had three guys as Copernicus, Kepler or Tycho Brahe to work with? Only those of the extremely limited human senses, and yet they produced something.

Yes, and the data they had was enough to produce what they did. A bunch of yearly measurements is all that's needed to derive Kepler's laws. A bunch of particles is all that's needed to derive the SM. To derive a TOE, you need data comparable to the scope of that goal.You might that the combination of all of GR and SM data should be enough. Not necessarily. If Kepler only had data from one of whatever he was measuring, it's very possible that wouldn't have been enough. Or if we had only detected half the particles we did before i don't know EW unification, maybe that wouldn't have happened either. Sure with hindsight a minimal amount of data seems required to derive a new theory, but it doesn't work that way. Same with string theory. Perhaps all that's needed is one low energy susy particle, or missing energy, or who knows, to guide us towards the correct formulation.

 

[MTd2]

Modern organized science in the form we know exists only since three max. four centuries. And since then I can't think of another theory in physics that was so revered, cherished and honored for a so long time without producing concrete results.

The scientific method, as we now it was first used by al Haytham, in the X century.

http://en.wikipedia.org/wiki/History_of_scientific_method#Ibn_al-Haytham

Anyway, I think you are not considering the quantity of data and the works that was not preserved.There was no printing and paper was hard to acquire. So, even important texts were erased, when not destroyed, for random uses. Take a look at this:

"Archimedes lived in the 3rd century BC, but the copy of his work was made in the 10th century AD by an anonymous scribe. In the 12th century the original Archimedes codex was unbound, scraped and washed, along with at least six other parchment manuscripts, including one with works of Hypereides. The parchment leaves had been folded in half and reused for a Christian liturgical text of 177 pages; the older leaves folded so that each became two leaves of the liturgical book. The erasure was incomplete, and Archimedes' work is now readable after scientific and scholarly work from 1998 to 2008 using digital processing of images produced by ultraviolet, infrared, visible and raking light, and X-ray.[1][2]"

http://en.wikipedia.org/wiki/Archimedes_Palimpsest

 

[marcus]

Since we've turned a page, I'll remind readers what the basic input data are that we are considering how to explain

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 as a fraction of total Particle Theory. It used to be that around HALF the first-time faculty hires in HEP theory were in string, now it's more like a tenth.

A physicist at the U Toronto (Erich Poppitz) charts first time faculty hires in High Energy Physics Theory (Usa and Canada) 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.
Here annual rates have been smoothed by averaging over 3 years intervals.

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

The source is http://particle.physics.ucdavis.edu/rumor/doku.php
A new webpage has been started that reports on postdoc fellowships in a broad category (gen. rel. and quantum cosmology) which includes quantum gravity. Also something to keep an eye on:
http://sites.google.com/site/grqcrumourmill/

There has been a decline in annual citations to recent string research by the theorists themselves.
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 currently refer to it. A kind of community self-evaluation, if you will, concerning the perceived value of current and recent work.

Several ideas have surfaced in this thread regarding possible reasons for the decline in interest. It's conceivable that reasons might be found in the physics of string itself. As an approach to reproducing the Standard Model, say, it might conceivably be fundamentally flawed on physical grounds. Arivero made the point that we should consider it separately as particle model and as a candidate theory of the quantum geometry of the universe.
In that second role, does it offer a promising way to resolve the cosmological singularity and model conditions leading up to the start of expansion? Is it testable by astronomical observation? This seems to be the main thing one wants a QG theory for. So there may or may not be valid physics reasons inherent in the theory.

Or it could simply be that newer approaches to QG and explaining the SM have arisen, and that researchers have some natural tendency to spread out seeking fresh ideas and new areas to work on.

We might get some good out of a special String retrospective issue of the journal Foundations of Physics edited by Gerard 't Hooft. He invited a reputable bunch of string and other theorists to contribute articles for an issue called Forty Years of String Theory.
http://en.wikipedia.org/wiki/Foundations_of_Physics
Some of the articles which 't Hooft invited to be in this special issue of the journal are available online:
http://arxiv.org/find/grp_physics/1...+co:+AND+string+AND+Forty+years/0/1/0/all/0/1

Additional help may be found by checking to see what topics interest String researchers these days, as indicated by the titles of invited talks which the the Strings 2012 conference organizers have put online:
http://wwwth.mpp.mpg.de/members/strings/strings2012/strings_files/program/talks.html
One assumes these are the topics which active researchers, the likely participants, are interested in hearing about and having discussed at the main annual conference. So we can get an idea of what they have in mind. For the past six days the list has had only one topic, but we can expect to see more appear shortly.

 

[MTd2]

Or it could simply be that newer approaches to QG and explaining the SM have arisen, and that researchers have some natural tendency to spread out seeking fresh ideas and new areas to work on.

This is a more likely explanation. But with a caveat: people are getting tired.

 

[negru]

For a rigorous analysis to prove that statement you should keep track of total number of citations in het+qg. Also h-index. In the past few years more and more garbage is showing up on the arxiv, from instituions i'll call sketchy at best.

I'd like to see evidence that papers and citations that in past came from string theory are now coming from alternatives. Just counting isn't enough. My own impression is that string people are doing SCFT's(amplitudes, localization, index stuff, a/c/f theorems), while newcomers especially from Europe are doing the alternative stuff. Also jobs are going to phenomenology related stuff, which is of course natural because of the LHC.

I'd also be curious to find out what job situation is in CMT to compare.

 

[mitchell porter]

But from a simple historical perspective, I'm wondering if there is a single example in the history of physics where hundreds, if not thousands, of top physicists worked on for more than three decades without producing a concrete result, and then turned out to be a correct theory? I can't think of any.

What is your opinion of grand unified theories and supersymmetric field theories?

 

[Aidyan]

A bunch of yearly measurements is all that's needed to derive Kepler's laws. A bunch of particles is all that's needed to derive the SM. To derive a TOE, you need data comparable to the scope of that goal.

How do you know what data threshold is needed? The data might well be already in front of our eyes but we can't see it because probably we don't want to give up our still too classical mindset. That's what happened to those who insisted on epicycles like Tycho Brahe, or to Poincaré who had all data and couldn't see relativity as Einstein did, or to Einstein himself with QM, just to mention some. I don't think it is only about available data, but about a message from nature we still don't want to swallow.

The scientific method, as we now it was first used by al Haytham, in the X century.
http://en.wikipedia.org/wiki/History_of_scientific_method#Ibn_al-Haytham
Anyway, I think you are not considering the quantity of data and the works that was not preserved.There was no printing and paper was hard to acquire. So, even important texts were erased, when not destroyed, for random uses...

You can't compare with the actual state of affairs the exceptional individual cases of some people who showed up from time to time throughout a centuries long period and that otherwise had almost no scientific progress. Organized science began with Galilei, Newton, perhaps even later. And since then, and also before that, there is nothing in history like the effort in terms of people, research and money set behind a single project like string theory *AND* with no concrete results.

What is your opinion of grand unified theories and supersymmetric field theories?

As I wrote, I'm not in a position to express too technical judgements apart of my doubts from the historical perspective (and BTW, if someone wants to help me: https://www.physicsforums.com/showthread.php?t=594293 ). I spent several years on applied physics and only recently turned my interests to more theoretical issues. But this happened just because of the "string crises". Intuitively I always perceived string theories as nonsense. I can only see in it the attempt of human mind to impose its naive classical aristotelian and anthropomorphic understanding of the macro-cosmos on a micro-cosmos that obviously refuses to be imprisoned in such narrow limits. But on the other side I always told myself: "those guys know better than you, they have certainly good reasons to believe in it, let me see...". But now, enough is enough... As to GUT they appeal certainly much more to my aesthetic sense. However, since they didn't produce concrete results either, this might be a lesson too: beauty is not a criterion. But something tells me that nucleons aren't stable, as predicted by several GUTs. I would keep an eye open on experiments looking for that.

 

[mitchell porter]

there is nothing in history like the effort in terms of people, research and money set behind a single project like string theory *AND* with no concrete results.

This is why I asked your opinion of GUTs and supersymmetric QFT - to see if you thought that they differ from string theory in this regard.

Let's recall another historically unprecedented situation: the existence of a single theory which does explain almost all of physics. This is the standard model, which has existed since the 1970s and has only needed the addition of neutrino masses, and a dark sector about which there is almost no data, to remain valid.

GUTs and supersymmetry and string theory have all grown up in the era of standard model dominance. GUTs are held to explain certain features of the standard model, like the hypercharge assignments; supersymmetry is supposed to give us dark matter, GUT coupling unification, and stabilization of the Higgs mass. Specific theoretical constructions give us, not the exact particle masses, but ratios between them with the right order of magnitude.

Nonetheless, none of these beyond-standard-model theories has yet become the new standard. It is a mathematical fact that there are innumerable possibilities to explore, even just within the framework of supersymmetric GUTs, because there are innumerable possible field theories which reduce to the standard model at accessible energies.

String theory has also turned out to contain innumerable possibilities, but they do have one new feature (apart from containing gravity): these distinct stringy possibilities do not come with continuously adjustable parameters, unlike field theories. Therefore, they are potentially more predictive than field theory. Unfortunately, like QCD, in practice it has proven very difficult to extract the predictions. The ability to calculate in string theory does progress, but this progress takes years to occur, and requires new mathematics.

There is continuity between the field-theoretic research program of unification and supersymmetry, and the research program of string theory, because the field-theory limit of string theory is typically a grand-unified supersymmetric theory. It has also been discovered that some field theories are simply equivalent to string theory on the specific corresponding background; the strings are essentially flux-lines in the field theory, and the extra dimensions emerge from scalars. It's likely that QCD itself is equivalent in this way to string theory on a particular background.

So reality does look a lot like string theory, because string theory looks like gauge theory plus gravity, and increasingly we also learn that gauge theories, like the standard model, look like string theory! It may be that some of the dominant physical hypotheses about how string theory works are misguided. Perhaps there's no supersymmetry, or no supersymmetry until ultra-high energies; perhaps the "extra dimensions" are algebraic rather than geometric. But it's also still very possible that the central hypotheses of the field are entirely correct. We might be living in a heterotic compactification with weak-scale supersymmetry, neutrino masses coming from the GUT scale, and so on.

When you say string theory has "no concrete results", I can't agree. What it has given us is a very large number of models which incorporate and complete the field theories that non-string theoretical physicists were already using, and which have the potential to explain the quantities which are just input parameters for something like the standard model. We know that string theory can get close to reality in various ways. One has every reason to hope it can go all the way.

 

[MTd2]

You can't compare with the actual state of affairs the exceptional individual cases of some people who showed up from time to time throughout a centuries long period and that otherwise had almost no scientific progress.

It was not casual. We lost a lot of information on those people. Only the very best survived because, as I said, the availability of recording media was extremely scarce.

 

[negru]

We know that string theory can get close to reality in various ways. One has every reason to hope it can go all the way.

Just an example off the top of my head, Heckman and Vafa compute the CKM matrix to within something like 1% from F-theory http://arxiv.org/abs/0811.2417

 

[arivero]

Organized science began with Galilei, Newton, perhaps even later. And since then, and also before that, there is nothing in history like the effort in terms of people, research and money set behind a single project like string theory *AND* with no concrete results.

If you are happy with 50 years without concrete results, then my previous example, the quest for quadratures of areas and cubatures of volumes, holds. Note that Kepler http://www.matematicasvisuales.com/english/html/history/kepler/doliometry.html Nova Stereometria doliorum vinariorum is from 1615, Cavalieri atoms, "Geometría indivisibilibus continuorum quadam nova ratione promota" are from 1635 and the final "concrete" results, Newton' "Analysis per aequationes número terminorum infinitos" and then the Principia, are from from 1669 and 1687. During this time, most of the Natural Philosophers (ie MathPhys), from Glasgow to Rome, were putting a lot of resources on this, and before Newton all they got was to confirm the Greek results and to add some extra examples.

Now I agree, that String Theory is near to break this record (and we will see if it gets something "concrete" out of it).

 

[Aidyan]

When you say string theory has "no concrete results", I can't agree.

With "concrete" in the case of ST I obviously meant "experimental evidence" which supports ST against other candidates, not just mathematical developments.

What it has given us is a very large number of models which incorporate and complete the field theories that non-string theoretical physicists were already using, and which have the potential to explain the quantities which are just input parameters for something like the standard model. We know that string theory can get close to reality in various ways. One has every reason to hope it can go all the way.

That's precisely what I find unconvincing. There are "various ways" to build a general theory that reduces to a previous one and yet turns out to be wrong. Especially if one is free to chose among a "very large number of models". Bohr's atomic model (which did "not come with continuously adjustable parameters" too) got 'close to the reality' in some respect. And Sommerfeld could refine it making it even closer to reality. But soon broke down because it couldn't account for the spectra of atoms much beyond Hydrogen. One can shows that it is possible to describe the observed planets trajectory on the sky with arbitrary precision all the way in a geo-centric model by adding epicycles to epicycles (very reminiscent of today's perturbative approaches...). But then Galilei brushed all this aside by observing the phases of Venus. Where would physics have ended by insisting on these paths because "reality does look a lot like..."? As long as you don't have the observational anomaly that can be explained only by one theory alone where all the others fail and that makes a minimum amount of testable predictions where all the other models predict something else, the argument of coming "close to reality in various ways" is week.

If you are happy with 50 years without concrete results, then my previous example, the quest for quadratures of areas and cubatures of volumes, holds.

As far as I know very concrete results were already obtained by a single philosopher like Archimedes with his exhaustion method. Cavalieri made some progress in between, and he furnished also some results. And Leibniz, Descartes and Newton followed giving us integral and differential calculus. These were steps where someone could do something out of it, not just a complicate theory about the world that was unclear if it was correct or not.

Note that Kepler http://www.matematicasvisuales.com/english/html/history/kepler/doliometry.html Nova Stereometria doliorum vinariorum is from 1615, Cavalieri atoms, "Geometría indivisibilibus continuorum quadam nova ratione promota" are from 1635 and the final "concrete" results, Newton' "Analysis per aequationes número terminorum infinitos" and then the Principia, are from from 1669 and 1687. During this time, most of the Natural Philosophers (ie MathPhys), from Glasgow to Rome, were putting a lot of resources on this, and before Newton all they got was to confirm the Greek results and to add some extra examples.

Now I agree, that String Theory is near to break this record (and we will see if it gets something "concrete" out of it).

What is there more "concrete" than estimating the prize of wine barrels? But it is interesting that to justify ST's supposed "slow success" one has to resort to dubious examples that are more than four centuries old. Do you have an idea in what miserable material, cultural and even more academic and scientific conditions was the world at those times? I live in the city where Galileo observed for the first time the Milky Way, the sun spots, and Jupiter's satellites. The historical documents tell that there was almost nothing here, apart from a hill with few houses, and that thing they called a "university". He did all alone by himself. There was nothing like large scale collaborations on a project, the universities, the laboratories, the institutions and organized science we have today. It is quite natural that scientific progress proceeded extremely slowly in those times. And yet, it is a miracle that these people could produce something tangible almost alone in the time span of a lifetime. I believe that string theoreticians should refrain from pointing at such examples, that doesn't make them look well...

 

[arivero]

I believe that string theoreticians should refrain from pointing at such examples, that doesn't make them look well...

Disclaimer, I am not a string theoretician. I just happen to be intrigued by the theory and my still current opinion, developed in other thread here , is that most of the important work was done in less than five years, say 1968-1973, and then they did a wrong turn towards Planck energy.