Causes of loss of interest in String program

marcus

Tom's thread "Why I'm REALLY disappointed..." continues to get increasingly thought-provoking and informative. I summarized some recent discussion here:
http://physicsforums.com/showthread....63#post3219363

I had some reaction to recent posts by Suprised and Tom that I will put in this side-thread because I don't want to overburden the main thread.

It is possible that there is a loss of interest among top creative people or loss of "research energy" in the program that is due to deficiencies in program management---failures of vision and direction: what Suprised calls "wrong turns" and "blind alleys". He also recalled the image of looking too much under the lamppost where the light is. We don't know that all of Suprised's diagnosis is correct, but he clearly knows what he is talking about and it is suggestive.

So has there really been a loss of focus or research energy? Has there been a loss of interest by top people? And if so, why?

marcus

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

Theories must be concrete, concise, and testable.
Even if they are recognized to be only a partial description of reality, they must give us something concrete to work with. Any theory of gravity must give a concrete picture of the accelerating expanding universe from its beginning. A theory of gravity is a theory of the geometry of the universe--how geometry evolves--so it has to give us a definite concrete model of the the universe to work with.

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

Background independence is a limited but useful concept, provided you know how to use it (without defensiveness and obfuscation).

It basically means "no prior geometry" (NPG) and to be that a theory must first of all be a theory. It has to have a definite formulation in a few principles and equations, so you can say "that defines the theory". Then on top of that the formulation must not resort to a prior fixed spatial or spacetime geometry. Typically that means no prior metric on the spacetime manifold

Because the classic GR theory of gravity/geometry can be (and is) formulated NPG, this concept is useful as a research GOAL. Basically the goal statement means "Be like GR" in that crucial way.

We all know that theories can have different equivalent formulations, the question is (if you have an actual theory) does your theory have an equivalent formulation that makes no use of prior background geometry?

It is difficult to apply this criterion to String because the String program has not produced a definite theory as yet. But it still could be useful as a goal.
The goal could be something like "get a concise definite theory of gravity that gives a concrete model of the expanding universe and has a positive Lambda (ie. acceleration) and is testable, and make it use no prior background geometry."

I think the concept of background independence is valuable to have as a goal.

atyy

Well, if physics is pragmatic and all that, perturbative string theory is perfectly fine (not my philosophy, just following your logic).

And loop is out, no Einstein equations yet, not pragmatic.

atyy

Looks like John Baez is still interested in strings http://math.ucr.edu/home/baez/susy/ .

Fra

I'm just trying to increase the perspective with this note. The lack of definite theory that's cleanly falsifiable without fuzz is a common critique against ST.

Lets just for the sake of argument, SUPPOSE that string theory is not a front level theory, but rather what some suggest a theory of theories.

An instructive question is they to ask, what does it mean to falsify a theory of theory? How do you know when a theory of theories is WRONG? Because suppose your theory defines one front line theory that is shot down, then you just have another one.

Do we need to change the notion of falsification? or is the notion of theory of theory simply baloney?

This isn't a trick question, I think it's a very relevat one. And one can reflect upon possible answers without taking side.

/Fredrik

marcus

Not my logic. I did not say theories should be pragmatic. I think physics should be pragmatic and incremental in the sense of proceeding in practical, doable, steps. Construct theories that you can test--gradually enlarge the areas of physical reality that we understand.

As I see it the main virtue of a theory of gravity is testability (in the area of cosmology, probably the only experimental arena). I would not necessarily require precisely reproducing the Einstein equations, but at least the theory should have a positive Lambda (accelerated expansion.) Just how I see it.

So is Edward Witten still interested . I'll get a count of his "string" and "membrane" papers over the past sixteen years 1995-2010

As I see it the String program may have lost energy because of misdirection, not by fault of theory per se. We aren't engaged in petty squabble games---tit-for-tat and pot-calls-the-kettle. If the management of the program has been deficient in vision and discipline (as Suprised suggests) we can objectively and constructively discuss this.

IF substantial numbers of top creative people have lost some of their earlier interest and focus, this could be a serious problem and it makes sense to ask WHY. Maybe this can be remedied (again I think Tom and Suprised are groping towards this idea of "back on track.") And if they have NOT taken what Suprised calls "wrong moves" and "blind alleys" and have NOT lost research drive then we don't have to ask why.

Here are the Spires links so you can make your own count if you like, using core string keywords "string model" and "membrane model".

http://www-library.desy.de/cgi-bin/s...=WWW&SEQUENCE= (38)

http://www-library.desy.de/cgi-bin/s...=WWW&SEQUENCE= (29)

http://www-library.desy.de/cgi-bin/s...=WWW&SEQUENCE= (9)

http://www-library.desy.de/cgi-bin/s...=WWW&SEQUENCE= (5)

Substitute other names if you like. Horava, Verlinde, Maldacena, Strominger...
Who knows what you will find? I haven't tried the experiment with these others.

Physics Monkey

I'm not convinced there is a loss of interest in the string program in general. There may be a (continued) shifting of interest into ads/cft kind of pursuits.

I just learned today that the most listed interest of would be theorists applying to graduate school at MIT is "ads/cmt". Of course, MIT is known for such pursuits, but its still an amazing sight. I don't know whether this is a good turn of events, but I do know that most of these people are basically planning on doing string theory or holography. So I have some informal evidence that strings aren't losing any steam, quite the contrary ...

atyy

marcus, you are missing the boat. The next big thing is AdS/LQG

marcus

Congratulations! This means you are way "ahead of the curve"! By some 4 or 5 years I would guess.
You introduced yourself in some other thread. Atyy I think it was mentioned the work of a MIT phd student in condensed matter intersection with AdS or something like that, and you said "That's me."

I forget the exact words but it sounded like just the specialty that most of the MIT applicants are now listing as their goal in graduate school.

As I recall there was quite a bit of Condensed Matter application of Stringy math featured in the invited talks lineup at Strings 2010.

So that seems to be hot. Good to be ahead of changing fashion!
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I think that the insight Suprised gave us, summarized here:
http://physicsforums.com/showthread....63#post3219363
does not refer to applications of stringy math to condensed matter.

When Weinberg talks about the String program being "disappointing", or Suprised talks about "wrong turns" and "potentially damaging" misdirection of effort, I think they are thinking of trouble with the unification program---the attempt to get a fundamental theory.

Same when Murray Gell-Mann expresses frustration and impatience with String program theorists not attacking the hard roadblock problems. I haven't seen an suggestion that anyone is disappointed with the String mathematical tools that have been developed and which seem rich in applications at various non-fundamental levels.

atyy

marcus, when you distinguish between fundamental and non-fundamental, you are talking like Weinberg. Have you ever read "more is different" (actually, I find that essay rather too truculent, but anyway). BTW, the thread you talk about above was actually about LQG/CMT.

marcus

Two great condensed matter theorists of our time---both with philosophical as well as physics insight: Phillip Anderson and Robert Laughlin. I respect them by (Nobel) reputation but I have not read books/articles by them.

I'm talking about something much simpler and really quite rudimentary. Not so sophisticated as what I think you have in mind.
If somebody applies String math to study superconductivity at the atomic/crystal level, then there is no need for them to include a positive cosmo constant Lambda in gravity. They ignore gravity, and most of the Standard Model. If AdS/CFT is applied to some condensed matter problem there will presumably be no difficulty choosing a mathematical model for the bulk. It's tools, not TOE.

atyy

In the context of Newtonian physics, Hamiltonians and Lagrangians are just tools too.

Also, think about Asymptotic Safety - that's presumably "fundamental" in your view, I assume. Yet it came out of condensed matter physics (admittedly CMT done by a HEP theorist, but we should count Kadanoff and a long line before that too, I think!)

marcus

That's a thought! Maybe you should give Witten, or Strominger, a pep-talk about the merits of the program. Say nothing is more fundamental that anything else so not to be disappointed if you don't find the ultimate reductionist theory of existence. Just kidding.

But empirically there does seem to be this loss of unification drive and direction that Suprised was discussing---this sense of "wrong turns". So I think it is worth thinking about what caused it. I'm thinking management--program guidance--vision. Maybe that's wrong. But there should be some explanation for it, and it may not be intrinsic to String per se.

You remember I listed Witten's "string" and "membrane" papers over the past sixteen years 1995-2010. Here are the same numbers for Strominger and Maldacena.

It looks like Witten shifted interest sooner than the other two. Here are the Spires links so you can make your own count if you like, using core string keywords "string model" and "membrane model". Just put in a different name instead of Witten and repeat the search.

http://www-library.desy.de/cgi-bin/s...=WWW&SEQUENCE= (38)

http://www-library.desy.de/cgi-bin/s...=WWW&SEQUENCE= (29)

http://www-library.desy.de/cgi-bin/s...=WWW&SEQUENCE= (9)

http://www-library.desy.de/cgi-bin/s...=WWW&SEQUENCE= (5)

rogerl

We will never get a handle of the fundamental theory by forcibly ignoring other phenomenon. For example. It is still complete mystery how the brain possess subjective experience. Our brain is just supposed to be pure biochemistry and circuitry. At most what you can get from this is unconscious processes and zombie like behavior, yet you have full qualia and subjective experience. If qualia is as fundamental as charge or mass, then it is part of physics and part of the Final Theory. By ignoring it completely and totally with no efforts to even entertain any notion of its possibility, we are pulling away from crucial ingredients that can nail the Final Theory. Decades ago. Topics like branes and stuff is considered taboo and physicists rise up their head away from them.. but now it is part of fundamental physics. It is possible that in 50 years time. They may discover qualia as being something fundamental and when it is integrated into the final theory like M-Theory, then everything locks into place. I don't know if it is related to Information Theory. Quantum, Relativity, 2nd law of thermodynamics is related to quantity, speed and quality of information. Anyway. Let's not talk about any of this here as these are presently taboo. But what I'm simply saying is not to ignore other possibilities just because a few entertain it. When Einstein discovered SR and GR, these were not even in the radar of physicists.

atyy

Well, you can always see what you want. I do it too.

marcus

I try to see as objectively as I can, forget about what I want, if I want to see anything.

But here it's pretty simple and hard to mistake. Almost everybody--physicists and physics watchers alike---must see the decline of expert interest in the String unification program.
Mature string theorists like Suprised are probably the most sensitively aware of it.*

The question is, what do you do about it. What should be done, at the departmental and funding agency level?

And in order to make constructive decisions one should try to understand why.

Maybe the answer has been already suggested by Physicsmonkey. As hypotetical example, suppose MIT were to admit to string-related PhD program only those applicants who were smart enough to see the drawbacks to writing thesis on string unification/phenomenology and were asking to study the application of stringy math to, say, superconductivity, or some other condensed matter.

Maybe that's the answer! Bail out of TOE and aim for applications. At the level of graduate school admissions policy, and at hiring committee, and at the funding agency. And smart MIT applicants would probably have a good idea of what the admissions people wanted to see, so they would be writing just the kind of applications Physicsmonkey indicated, for whatever reason. It is hard to distinguish cause from effect sometimes.

That is one scenario. But I'm trying to think how to cure the problem rather than just avoiding it. Suprised listed a bunch of what he thought were potentially destructive "wrong turns" that could explain. If S. were right, and the administrators committees directors chairmen etc knew he was right, they could remedy the problem and get the program steaming ahead on track. That may sound optimistic but I think it's more interesting to speculate about.
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*Longtime string theorists must be among the most aware of the decline in expert interest, an indicator being how the theorists themselves rate the value/interest of their own colleagues' string research papers. This is shown e.g. by how many recent string papers (past five years) are cited enough to make it into the Spires HEP top 50. A substantial fraction of the Spires annual Top Fifty used to be recent string research papers.

So I conclude that Suprised, who has been in the String program 25 years, must be more poignantly aware of unification program decline than any of the rest of us.

Spires top cited articles during odd years 2001-2009
(with number of recent string papers making the top fifty shown in parenthesis)

http://www.slac.stanford.edu/spires/...1/annual.shtml (twelve)
http://www.slac.stanford.edu/spires/...3/annual.shtml (six)
http://www.slac.stanford.edu/spires/...5/annual.shtml (two)
http://www.slac.stanford.edu/spires/...7/annual.shtml (one)
http://www.slac.stanford.edu/spires/...9/annual.shtml (one)

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

atyy

My point about Lagrange's and Hamilton's work was that although it was just tools in their day, that laid the understanding for what was fundamental in the next era. In other words, before Newtonian mechanics could be generalised, it had to be understood.

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

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