In a new preprint of an article entitled “So what will you do if string theory is wrong?”, to appear in the American Journal of Physics, string theorist Moataz Emam gives a striking answer to the question of the title. He envisions a future in which it has been shown that the string theory landscape can’t describe the universe, but string theorists continue to explore it anyway, breaking off from physics departments to found new string theory departments:

So even if someone shows that the universe cannot be based on string theory, I suspect that people will continue to work on it. It might no longer be considered physics, nor will mathematicians consider it to be pure mathematics. I can imagine that string theory in that case may become its own new discipline; that is, a mathematical science that is devoted to the study of the structure of physical theory and the development of computational tools to be used in the real world. The theory would be studied by physicists and mathematicians who might no longer consider themselves either. They will continue to derive beautiful mathematical formulas and feed them to the mathematicians next door. They also might, every once in a while, point out interesting and important properties concerning the nature of a physical theory which might guide the physicists exploring the actual theory of everything over in the next building.

Whether or not string theory describes nature, there is no doubt that we have stumbled upon an exceptionally huge and elegant structure which might be very difficult to abandon. The formation of a new science or discipline is something that happens continually. For example, most statisticians do not consider themselves mathematicians. In many academic institutions departments of mathematics now call themselves “mathematics and statistics.” Some have already detached into separate departments of statistics. Perhaps the future holds a similar fate for the unphysical as well as not-so-purely-mathematical new science of string theory.

This kind of argument may convince physics departments that string theorists don’t belong there, while at the same time not convincing university administrations to start a separate string theory department. Already this spring the news from the Theoretical Particle Physics Rumor Mill is pretty grim for string theorists, with virtually all tenure-track positions going to phenomenologists.

I have some sympathy for the argument that there are mathematically interesting aspects of string theory (these don’t include the string theory landscape), but the way for people to pursue such topics is to get some serious mathematical training and go to work in a math department.

The argument Emam is making reflects in somewhat extreme form a prevalent opinion among string theorists, that the failure of hopes for the theory, even if real, is not something that requires them to change what they are doing. This attitude is all too likely to lead to disaster.

**Update:** A colleague pointed out this graphic from Wired magazine. Note the lower right-hand corner…

**Update: ** Over at Dmitry Podolsky’s blog, in the context of a discussion of how Lubos’s blog makes much more sense than this one, Jacques Distler explains what it’s like for string theorists these days trying to recruit students:

Unfortunately, I’ve seen a number of prospective graduate students, who spent their undergraduate days as avid readers of Woit’s blog, and whose perspective on high energy physics is now so hopelessly divorced from reality that the best one can do is smile and nod one’s head pleasantly and say, “I hear the condensed matter group has openings.”

I have some sympathy for the argument that there are mathematically interesting aspects of string theory (these don’t include the string theory landscape)The string theory landscape (i.e., the space of string vacua) is, from another point of view, a space of 2d CFTs. Why isn’t that an interesting mathematical object?

anon,

Maybe there’s some interesting global structure to the space of all 2d CFTs, but people have been looking for such a thing for years and I don’t see any progress. In any case, that’s not what people working on the landscape are doing, instead they’re looking at specific points or neighborhoods in this space, and these are typically not mathematically very interesting.

Somehow I have a hard time seeing grad students and undergraduates beating down the door of admissions clamouring to be part of a program in this new department of not-physics-not-math.

hmm, a new department claiming to have insight into the nature of reality, but not mathematics, not physics … does he really think the philosophers are going to let them horn in on their territory like this?

I am having a big problem with this:

… if a mission that you have been embarked on for over thirty years turns out to be futile then dumping it is not only sensible – it is a

moral obligation.But maybe it’s what they should be doing. (Well, some do, but not those in the string theory departments.)

A theory is independent of what people do about it. If all present attempts to address open question X are inadequate, it doesn’t necessarily imply that question X is uninteresting.

Hey! Adrian is going back to NY!

Reg the question what would the string theorists do in case. Well, one couldn’t just fire all these string theorists, what were they supposed to do? If they were able to, they might change fields, but we all know this isn’t easy especially if the education has been narrow and one has passed the fifty or so. Maybe one should offer a re-education program or something. There is without doubt a strong specialization going on in the community. Many of these people are extremely smart and could make contributions to many other fields, but who is going to hire somebody who has worked 10 years on string theory for, say, an astrophysics position?

That being said, I too would guess that those who couldn’t jump off the field but could keep their job would just continue working on it. Well, you know what they say, progress isn’t made from conference to conference, but from funeral to funeral. Maybe string theory would become an art form, or a branch of philosophy? Who knows.

Well, astrology has been proved to be wrong, but I’d say there are more astrologers out there than astronomers, and for certain they are making more money than the latter, so I’d not be surprised.

Now, seriously, if string theory turns out to be proven wrong, I hope people who devoted they careers to it are reasonable enough to pursue other lines of research, or at least admit that string theory is pure mathematics and treat it as such.

I think an equally appropriate question Peter is what would you do if string theory is shown to be correct? 😉

piscator,

Doesn’t seem to be going that way, does it? But if it does, probably I’d keep working on the same things I’ve been working on for years. Maybe I’ll pay less attention to gauge groups and more to Diff (S^1)….

Poor Witten.

Peter wrote:

> Maybe there’s some interesting global structure to

> the space of all 2d CFTs, but people have

> been looking for such a thing for years and

> I don’t seen any progress.

Isn’t the space of superconformal field theories

supposed to be the topological modular form spectrum? Work of Hopkins, Lurie, Teichner and Stolz etc. Maybe not of physical interest but algebraic topologists are very excited about this, I think.

It sounds like Clinton: I lost but I stay…

🙂

Maarten,

Sure, if you look at special classes of 2d CFTs, you get extremely interesting mathematics, one example is the one you mention. The problem is that the class of CFTs the landscape people are interested in because it is supposed to unify physics doesn’t seem to be a mathematically interesting one.

This has always been the problem with string theory: some parts of it lead to deep and wonderful mathematics, but those have always turned out to be orthogonal to the parts of string theory you get into when you try and use it to unify 4d gravity and the standard model.

Peter, have you looked at Witten’s talk at the ongoing Dark energy symposium at

STSCI

Is there really anything wrong with that?

“Well, we had an interesting idea, and gave it a go, but it doesn’t look like it panned out. Still, this is a fun system to play with, and we think that we’ll keep playing with it, even if it doesn’t have any relation to physical reality.”

Of course they’re going to have to stop calling it physics, which they’ve agreed to. But how is this less “valid” than, say, searching for all of the Mersenne primes? Or, for a physics analogy, solving mathematically interesting cosmologies that simply don’t happen to be ours?

Thanks Shantanu, very interesting. Maybe I should write a blog entry about that…

Ethan,

Sure, anybody whose research program fails is welcome to decide that he or she wants to keep going anyway. The problem I’m trying to point out is that it is unlikely that either the physics or math communities are going to support this. So, unless you’ve got tenure and don’t care whether you have a grant and graduate students, you’ll probably find that you can do this but no one is going to pay you to do it, or hire any students who work with you on it.

I have seen some string theory physicists do exactly that: study maths, become mathematicians, and keep working on problems they find interesting for physical reasons. They have the bonus advantage of being able to speak (or at least read) “physiquese”, something most pure mathematicians (like me) usually can’t do and occasionally is useful.

The big question is: “When string theory is proven not to correspond to physical reality, will any journals publish research on string theory?”

I think string theory is still an excellent topic for graduate students at this time.

Since string theory contains both QFT and GR, and also some math, one can switch to these three fields later on.

If the LHC finds a simple higgs-sector, which will be theoretically explored in relatively short time, phenomenologists will have problems, because there won’t be many problems left to solve..

I dont think that a phenomenologist can become a mathematician, or a researcher on pure quantum gravity.

Where as i think it is sure, that it can be expected from a string theorist, he can switch to mathematics, phenomenology, pure quantum gravity, or genral relativity.

http://xkcd.com/171/ !

“Well, we had an interesting idea, and gave it a go, but it doesn’t look like it panned out. ”

Well, this is pretty much what we wanted Witten and others say for a decade. With the notable exception of Dan Friedan, no string theorist has been willing to say it, though.

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>Benni Says:

>I think string theory is still an excellent topic for graduate students at this time.

>Since string theory contains both QFT and GR, and also some math, one

>can switch to these three fields later on.

It isn’t easy or practical for some people to switch academic fields without some kind of temporary position, such as a postdoc in the meantime. If string theorists don’t get postdocs, they usually have to leave academia fairly.

> I dont think that a phenomenologist can become a mathematician, or > a researcher on pure quantum gravity.

Though I am not a phenomenologist, I know that some of them certainly could make such a move.

Fairly quickly, I meant.

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“Where as i think it is sure, that it can be expected from a string theorist, he can switch to mathematics, phenomenology, pure quantum gravity, or genral relativity.”

that’s like saying a 100m sprinter could switch to american football, or rugby.

Today, Alvarez Gomé gave a talk in Munich about the riddles in fundamental physics. He tried to make of the “self-righteous popperazzi”; but in fact he seemed very hurt by the critics of string theory, including Peter, whom he mentioned at the beginning of his talk, together with Lee Smolin.

He also made an interesting and strong statement that was new to me: only string theory can explain gauge theory. Asked why, he stated that string splitting/breaking is equivalent to a gauge theory.

In the introduction to the talk, Dieter Lüst explained that a new faculty position on “higher dimensions” is available in Munich. A faculty position on something unobserved. Times are bizarre …

Bjoern,

When I was in Lisbon last fall I had the chance to talk to both Lust and Alvarez-Gaume, and we had some interesting and worthwhile discussions, which were polite but sometimes forceful. Alvarez-Gaume is certainly not happy with all the criticism that string theory has been getting. As a leader of the CERN theory division and a string theorist, I’d guess the public criticism and change in attitude has made his job significantly harder and put him on the defensive.

Unfortunately, I think this has made him focus on some of the unfair criticism string theory has gotten, and upon making a forceful defense, instead of acknowledging that there is a legitimate problem to be discussed. I don’t know exactly what claim he was making, but the statement that “only string theory can explain gauge theory” is simply not true. Going too far in its defense is not going to be helpful to the interests of either string theory or of particle theory in general.

I’ll update the old joke:

The dean of the school of science was scolding the chairman of the physics department:

“Why,” he asks, “does it cost so much money to run your department? Why must you purchase all this equipment?

“Why can’t you be more like the math department. They only need pencils, paper and garbage cans. Or better yet, like the string theory department! They only need pencils and paper…

In the words of Einstein, “I would be sorry for the dear Lord. The theory is not wrong!”.

Thomas R Love,

If mainstream particle theory journals ever ceased to publish string theory papers, then most likely the remaining string theorists will start their own “peer reviewed” journal dedicated to string theory.

It is nice to see scientists writing papers on philosophical or foundational issues and in this respect Emam paper is quite welcomed. As for the content, I did not find the paper very convincing. At present, both a success of string theory or its failure are well beyond the horizon. A failure will most likely not be of the form of a single bit of information coming from the sky, but probably will be related to major other developments, theoretical or empirical, and thus will probably give people in the field a lot to work on.

Peter,

indeed, your description of Alvarez-Gaumé’s feelings is precisely the same that I got in his talk. My opinion is that there is a huge difference between saying “string theory is useless because it makes no predictions” (as you do) and attacking string theorists personally (AG mentioned a ferocious literary critic called “Steiner” which must have offended him in a public meeting recently).

It is important for one’s personal image and also for one’s personal well-being to keep and upheld this difference.

AG was also annoyed by the statement “the end of science is there” (citing John Horgan explicitly) and explained how many open problems there are in biology, chemistry etc.

I looked again into my notes. I did not copy the exact statement from his slide, but he really made the statement that no other theory except string theory explains gauge theory from a more basic point of view. The question that was asked only asked how string theory deduces gauge theory. Why no other theory does so was not addressed.

Nevertheless, Alvarez-Gaume was well-balanced, and I am sure that one can have interesting professional discussions with him.

Bjoern

P.S. In my first post, the sentence should have read: “He tried to make fun of the …”.

Bjoern,

The conference in Lisbon I was referring to was organized by George Steiner, and John Horgan also spoke. Both had quite critical things to say about string theory, but neither is a physicist (Steiner is a literary critic, although somewhat of a polymath).

Bee says “Reg the question what would the string theorists do in case. Well, one couldn’t just fire all these string theorists, what were they supposed to do?”

Well, you certainly can’t fire a lot of them … they have tenure. I believe that pretty much the only way to fire tenured faculty (if they aren’t guilty of gross misconduct) is to dissolve the department they are in. So if Moataz Emam gets what he is wishing for, and university adminstrators start creating Departments of String Theory, I would say this would be very bad news indeed for string theorists.

yes, yes and just imagine what will happen to mathematics departments if a contradiction in mathematics will be found.. and if the view regarding the “end of science” will previal we will have to rename “science faculties” to “post-end science faculties”…

Seriously, I am skeptical if this type of fantasies are the right avenue for skepticism in science, which shoud be welcomed.

yes, yes and just imagine what will happen to mathematics departments if a contradiction in mathematics will be found..Indeed… who could imagine how mathematics departments would cope if such a strange, unheard-of thing were to happen?

I think the thing to keep in mind here is, mathematics disciplines can validly motivate themselves entirely on internal metrics of progress. You can have subjects in mathematics putter along happily for years in the complete absence of any practical application, and no one really minds. If you’re going to describe yourself as

physics, though, it’s not enough to be internally consistent. You also have to coincide with what is true in the real world. And the real world simply happening, coincidentally, to not be the same as some theory or other is a real, constantly looming possibility which needs to be taken seriously for all physics theories– even established ones, I think.(I personally would find string theory a lot more interesting if it did jump ship and decide to become a mathematics discipline rather than a physics one. As Woit notes above there are some rather interesting bits of math in string theory but they get overshadowed if you think about string theory as a way of unifying physics. Like, I want to know more about these “fractal string” things. And isn’t it true that even if String Theory is “proven wrong” as a physics unification theory, AdS/CFT will continue to be a relevant mathematical tool in physics?)

and if the view regarding the “end of science” will previal we will have to rename “science faculties” to “post-end science faculties”…Heh, this is a fun point though. I wonder if Post-Science is similar to post-modernism or post-rock.

I found this quote:

I can now rejoice even in the falsification of a cherished theory because even this is a scientific success

—John Carew Eccles

Rejoice!

Dear Peter

I’ve got an impression that the question “what will you do if string theory is wrong” as you presented it actually sounds empty. To define whether string theory gives the wrong answer to the question you ask, you first need to ask the question.

If your question is “does landscape have anything to do with objective reality”, then the answer could be very well “no” (although it could very well be “yes”).

If your question is “does string theory have anything to do with strongly coupled regime of gauge theories or, say, 3D Ising model”, then, I guess, the answer should be already known to people around.

I think, if landscapism will eventually die out, string theorists will start working on problems requiring string theory to solve them such as strongly coupled YM.

Cheers

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Dmitry,

I’m not the one going on about “string theory is wrong”, what I was doing in this posting was linking to an article by a string theorist on this topic. “String theory” now refers to a huge array of different kinds of things, from the quite interesting to the nonsensical. The statement “string theory is wrong” is meaningless, and not one that I make.

To respond here to the posting on your blog, I’d like to point out that your characterization of what I wrote here as: “String theory is wrong, all string theorists should be immediately fired” has nothing to do with what I actually wrote or what I think. At least you’re not referring to me as “Peter Whore” or calling for my death, but you are adopting Lubos’s tactic of drastically misrepresenting the arguments of other people.

The gist of my comment on the article here was that the idea that string theorists should give up on being part of physics departments and start their own separate departments is unrealistic, since virtually no university is going to fund this. The comment that this year in the US virtually all tenure track theory jobs are going to phenomenologists, not string theorists, is simply factual and not made as a value judgment. The kind of work that I think needs to be done, deeper formal investigations of quantum field theory, is every bit as unpopular as string theory, and tenure-track jobs are not going to people doing this either.

If your question is “does string theory have anything to do with strongly coupled regime of gauge theories or, say, 3D Ising model”, then, I guess, the answer should be already known to people around.Does string theory have anything to do with the 3D Ising model? If so, what? Can you use it to extract some numbers exactly? If so, which numbers and what are their values?

CFT has of course a lot to do with 2D Ising, but that is an almost trivial toy model in comparison.

Dmitry,

Rereading your blog posting, I see that you are also completely misrepresenting Peter Shor’s comment. He was not regretting that string theorists cannot be fired “because they are on a tenure track”. He was pointing out that separate string theory departments would be dangerous for string theorists, since essentially the only way US universities can (and do) fire tenured people is by closing down their department. If string theorists had 20 years ago organized themselves into new separate departments, there would be a danger now that universities would start closing these.

And, just being “on a tenure track” does not at all make it difficult to fire someone, they need to actually have been tenured.

Peter,

Regarding the issue of faculty hires this year, don’t you suppose that the reason phenomenologists have been hired has something to do with the fact that LHC is about to turn on for the first time? It seems a little dishonest to me to intimate as you do that this is a sign that string theorists are falling out of favor. Once the results from LHC are in, then we should probably expect more string theory hires if all goes as expected.

Peter

If I misitepreted your or Peter Shor’s words, I apologize. Nevertheless, your post left me with a particular impression (and I have to confess that it did not dissolve), and that was the reason why I wrote what I wrote.

Thomas

For 2D Ising, there are two equivalent formulations of the theory: in terms of spin variables \sigma and in terms of disorder variables \mu (the ends of dislocation lines). Although \sigma and \mu satisfy rather complicated equations, their product satisfies linear equation; that fact allowed Onsager to find exact solution of the 2D Ising model.

For 3D Ising dislocation lines become dislocation surfaces, boundary of such surface is the variable on which disorder variable \mu depends. One hope to find simple equations describing 3D Ising is to construct product of \mu (C) and \prod \sigma (x_i) where x_i are points close to the loop C. The first impression was that such a loop C together with “spin” variables – vectors normal to loop and connecting it with points x_i – is NSR string, and the equation describing its dynamics is linear in the space of loops.

One person who tried to pursue this program was Polyakov. As far as I know, he got stuck since it was hard to write equations in loop space for renormalized variables.

Thomas,

This is off topic and Peter may want to delete your comment and mine – well not SO off topic. You were asking about the application of string theory to field theory/stat. mech. problems. I have worked on this sort of thing on and off for a long time. It may not be much off the main topic, because it does touch on the justification for continuing to do string theory, should the subject fail to unify forces or give definite results in quantum gravity.

There was a program initiated by many people – Nambu, Weingarten, Hasslacher and Corrigan, Makeenko and Migdal, Polyakov … the list goes on – that gauge systems like QCD and the 3D Ising model (which is dual to the Z_{2} gauge theory) could be solved using string-theoretic ideas. There are exact representations of the 3D Ising model as random surfaces with a certain action.

This program only seems to an unqualified success for N=4 susy YM. It has not yet panned out for pure Yang-Mills (which one wants to solve at weak bare coupling, near the RG fixed point, not strong bare coupling) or finding exact results for 3D stat. mech. systems. If you want critical exponents for statistical models in 3D, epsilon and 1/N expansions are still your best bet.

In fact, it is much easier to obtain string-like excitations from field theory than the other way around. The examples are strongly-coupled lattice theories, Higgs theories with vortex strings, compact QED in 2+1 dimensions and recently SU(N) gauge theories with two small couplings (sorry to advertise my own work Peter). These string-like excitations have not been shown to have any connection to standard string theory. When actions can be written down, they contain extrinsic-curvature-dependent terms, and are not local on the world sheet.

Maybe someday some of these long-standing problems will be solved using standard string-model ideas. Personally, I hope so. But maybe not.

Peter Orland, I have zero interest in the “justification” issue. Just wanted to comment that there are new ideas on the market relating various 3dim systems to string theory, via the gauge-gravity duality. These may or may not pan out, but they are different from the set of ideas you refer to (more to do with perturbative ST). For an entry point to the literature you can look at recent papers of the nuclear theorist D.T. Son.

Hi Moshe,

Yes, I have seen this stuff – but these systems are interesting because of their connection to string theory. I am not convinced they have any application to nature (I know people are trying to make such a connection).

Regards,

Peter

P.S. The effective string excitations, which arise in field theories, also

have no obvious connection with perturbative string theory.