The Pacific Institute for Theoretical Physics, based at UBC in Vancouver, held a Showcase Conference a couple weeks ago, which was supposed to “celebrate the exciting new developments taking place in theoretical physics”. According to the organizers there are lots of exciting new developments in string theory, since six of the invited speakers (Myers, Ooguri, Randall, Schwarz, Shenker, Susskind) spoke on that topic, but no one at all spoke about elementary particle physics. There were also quite a few talks on condensed matter physics.
The talk of John Schwarz consisted mainly of the standard recounting of the history and basics of string theory that anyone who has been to conferences like this has heard a hundred times. This part stopped with Maldacena’s work more than 7 years ago. On more recent topics, about the anthropic explanation of the cosmological constant, Schwarz says: “Is there another explanation? I hope so.” He ends by putting up a long list of questions about string theory, more or less the same list everyone has had for twenty years now.
Steve Shenker spoke on Emergent Quantum Gravity, with “emergent” the new buzzword of the field. There was a separate workshop on emergence overlapping with the Showcase conference, organized by Phil Anderson and others, with Susskind the only string theorist allowed to speak there. Shenker introduced a new terminology to justify string theory: it is “An algorithmically complete, consistent description of quantum gravity”, although he does add the caveat “In certain simple situations (like flat space)”. By this I guess he is trying to get around the problem of how to claim that your theory is complete and consistent when you don’t know what it is. The idea is that at least you have an algorithm for doing computations. Perhaps he means perturbative string theory, although that is neither consistent nor complete (the expansion in the number of loops diverges). Perhaps he means a non-perturbative formulation like a matrix model, which works in 11 flat dimensions, but then he really should note that he’s not talking about quantum gravity in four dimensions, which is what most people care about.
There was an interesting panel discussion on The Theory of Everything?, which was moderated by Steve Shenker. He seemed mainly interested in making the obvious point that string theorists weren’t actually claiming that their theory explained anything about, say, biochemistry. The panel was actually balanced between string theory enthusiasts (Shenker, Schwarz, Randall), and skeptics (‘t Hooft, Unruh, Wald). Some of Shenker’s introductory remarks are inaudible, but he did repeat his claim about the “algorithmically complete” nature of string theory. “t Hooft had some quite interesting comments. He recalled that at a conference back in 1985 he had been the only one who didn’t think that twenty years later string theory would have solved all the problems of particle physics, noting that it was now 20 years later, he had been right, everyone else at the conference wrong. He was making the point that string theory now is extremely far from solving any problems in particle theory, and one can’t tell if this situation will change in 20, 200 or 2000 years. He tried to say some positive things about string theory, but they were pretty half-hearted. For instance he noted that dualities were very interesting, but they linked one ill-defined theory to another ill-defined theory. He also noted that in its present formulation string theory is only defined on-shell, which he takes as meaning that it doesn’t give a true local description of what is going on. He has reasons for being suspicious of people who claim that all one needs is an on-shell theory.
Schwarz attributed the TOE terminology to John Ellis. He said that he feels string theory is very far from explaining anything about elementary particle physics, that it was “almost hopeless to find the right vacuum”. He described what landscapeologists are doing in a skeptical tone, but didn’t actually criticize this. Answering ‘t Hooft, he claimed that back in 1985 he and Mike Green were actually more pessimistic than most other people about the prospects for getting quick results out of string theory.
Bill Unruh made the standard criticism that what is wrong with string theory is that string theorists are motivated by beautiful math, not physics. He doesn’t seem to have noticed that few string theorists are now doing math, since unfortunately most of them have taken to heart the criticisms of people like him. The failure of string theory has unfortunately reinforced the skepticism of many people like Unruh about the use of math in theoretical physics.
Wald quoted what sounded like a recent description of what string theorists think they are doing, then revealed that his quotes were from the 19th century, and referred not to string theory, but to the popular theory of the time that atoms were vortices in the ether. He deftly made the point that it is quite possible, if not likely, that string theory is just as wrong an idea as the vortex one.
Lisa Randall made some defensive comments about string theory as a guide for future research, even if it turns out not to work. These included the bizarre political analogy that it was wrong to worry about string theory ruining the credibility of physics, because, after all, the bogus WMD business didn’t seem to have hurt Bush’s credibility.
There were then some questions and comments from the audience. Susskind was in the first row, looking very peevish and defensive. He kept repeating that the field of theoretical physics had “no real choice but to track this down”, meaning to investigate the infinite landscape, and that this would take the efforts of many physicists. He explicity worried that funding agencies would not give any grants to anyone working on the landscape, to which Unruh responded that the shoe was really on the other foot, with some NSF panelists refusing to fund anyone who wasn’t doing string theory.
The conference web-site also includes an explanation of string theory which claims that in recent years string theory has “evolved very rapidly”, that the reason it can’t be tested is because of the small distance scales involved, and that it may be testable by observing a “5th force”, all of which is a load of nonsense.
Lubos Motl has an interesting post going over all the possible ideas he can think of that might lead to the next superstring revolution. Needless to say, they all sound extremely unpromising to me. Judge for yourself. He also quotes the promotional material for Susskind’s book due out late this year. It seems that “the Laws of Physics as we know them today are determined by the requirement that intelligent life is possible”.
Questions such as corrections to scattering amplitudes (via E-p relationships)
I don’t believe a scattering amplitude has ever been computed in LQG
BH entropy (including computation of logarithmic corrections, etc)
LQG has not computed the black hole entropy either. There has not even, to my knowledge, been an identification of a black hole state in the theory.
Hawking radiation, elimination of ultraviolet divergences in QFT, cosmological inflation, unobserved supersymmetry, and others are best explained in LQG;
LQG has next to nothing to say about any of these.
CY is just a “standard” differential manifold. The substitution of macro spacetime by a kind of quantum foam was first introduced in LQG, etc.
This goes back to Wheeler and possibly before.
Even possible violations of unitary were first introduced in LQG and only recently in certain noncommutative geometries in brane theory.
Unitarity violations are also an old idea. String theory, on the other hand, really is unitary.
And this is what I mean by LQG hype….
Chris,
Thanks for the advice, motivating myself to work on stuff that I’m not really wanting to do is one of my biggests problems my plan is to apply to whichever grad schools will give me the most freedom in my research. Speaking of motivating myself to do things i’m going to go finish my lab write-up.
Previous comment was a mortain comment; accidentally omitted pseudonym.
Yes, anonymous, I am frustrated. I’m glad I’m not the only one. Thank you for your comment on this (it’s helped).
To Scott: yes, I think you are entering at a good time, too. Hopefully there will be lots of experimental discoveries soon, leading to new theories and a reshaping of fundamental particle physics. Maybe the LHC is just what we need to oust string theory, perhaps analogously to Michelson-Morley’s experiment demolishing the aether. I got my PhD two years ago, by the way. I wish I’d been reading a blog like this as an under-graduate!
Hey, Chris, I did just that… and afterwards got nowhere very fast in physics or in life, sadly.
“What if the failure of quantization of GR is on that GR is not correct after all?” That is a worrying thought, at least for me, Juan R. I suppose the converse, as far as conventional approaches to QG go, is Penrose’s kind of view, i.e. that QM requires modification, and not GR. Either way, I find possibilities like these very discomforting. One fact I’ve never gotten over is that some special materials (whilst in Earth’s gravitational field) do not obey GR [see, e.g., Clifford’s article in ‘300 Years of Gravitation’]… what’s that all about!? Just quantum corrections to GR, or a problem with GR?
Peter, was it Pauli or Veltman-quoting-Pauli who inspired your blog’s name? If string theory did die, would you change the name of your blog? I believe that your blog would be no less interesting or worthy if string theory didn’t exist. Incidentally, did you notice that Peter Lax won the 2005 Abel Prize this month? I’m almost certain that you made posts about the other previous Abel Prize winners (all three of them), and I wondered if you were planning a post about Lax.
I’ve been following a lot of the string theory news for years now in the press as well as in the arXiv (with very limited understanding) and by searching the internet for articles and blogs. It seems to me that there are a few camps out there with particularly strong views either in favor of this theory or that theory, and frequently they take their theories and any challenges to their theories quite personally, which I suppose is fine, as long as it contributes to the progress of science.
On the other hand, it seems that the politicization [sp?] that is so prevalent in the US now with the Conservatives and the Liberals squaring off in every possible forum is spilling over into high-energy physics theory. Is this how things were in the early days just before the quantum revolution, or is it somehow different?
To me the picture of an ideal physicist is someone who is deeply interested in understanding how nature works, and does so objectively, and realizes that despite the advances that science has made so far, nature always seems to throw a few curve balls in with every round of pitches, and we have to be prepared for them, if we hope to hit a home run.
Some one said:
“But the culpable of failure of stringy endeavor is not Nature, nor Lotto, nor Peter, nor Glasgow, nor Phil, nor… nor this ignorant called Juan R. The problem was the arrogance of string theorists.”
No, no one is a culpable of the stringy failure and no one should be held responsible for the “failure”. Nature is the nature way it is and it would not have changed anything because somethign the researchers have tried or have not tried. If the nature is not 10-D, then it is not 10-D, and you can get a super-Einstein to research string theory, and he would not get anything different. He would not be able to force the nature to become 10-D. Only God can do that.
Actually I think the word “failure” is not even the correct word to describe the current status of string theory. Failure is the kind of thing that has an outcome dependent on what you do. You do or behave in a correct way you succeed, and you do it a different way you fail. If there is a treasure island out there and you could not find it. It’s a failure. But if there is no treasure island to start with, then it’s not a failure but simply reality.
The string theory is the later case. It’s not a failure. It is simply reality. The reality is the world is 4-D, not 10-D. Plain and simple. And some people can not accept that reality.
Quantoken
At least Aaron every now and then takes the time to drop a note here whose author is actually familiar with what he is talking about. He should be honored for that.
Scott,
Observations like the one I made below (at 05:16) are so obvious that no-one should need to make them. The fact that someone has to is indicative of the groupthink mentality of string theorists. I think that you are right to want to follow your own lights, stringy or not, and I applaud you for it, but my advice – for the sake of your own sanity – is to be prepared to go quietly and gracefully after your Ph.D. if you fail to find like-minded individuals within the establishment who are prepared to support you.
Wow Aaron way to fuel the fire. While I can’t speak for mortain I can tell you that I didn’t first decide that i wouldn’t go into string theory from this blog, nor does all of my limited knowledge in strings come from it. I first decided that it definately wasn’t for me after my freshmen physics seminar course where Schwartz’s answers to my questions about predictions and testability were very disatisfying as were the reasons to pursue string theory that he gave(and all the ones i’ve read of sence then and before for that matter). I don’t like your assumptions that i am incapable of thinking for myself and was tricked by peter. This I also found rather unappealing:
“there’s not much market for the sort of speculation that could lead to a new direction — that sort of thing, much like the interpretation of quantum mechanics, should be left to the tenured.”
If there is no “game” in physics(particle or cosmology) that attracts me I plan, and already have a couple of spare ideas floating around my head that need development, on making my own “game” or I will fail trying untill someone else makes a “game” i’m interested in, whether the tenured want me to or not.
like chris said just cause this one model of how you think things might work is unpredictive doesn’t mean there isn’t another model out there that is, me I’m going to keep looking for that next model.
Aaron Bergman, string theory has not been more successful that LQG.
Questions such as corrections to scattering amplitudes (via E-p relationships) BH entropy (including computation of logarithmic corrections, etc) Hawking radiation, elimination of ultraviolet divergences in QFT, cosmological inflation, unobserved supersymmetry, and others are best explained in LQG; CY is just a “standard” differential manifold. The substitution of macro spacetime by a kind of quantum foam was first introduced in LQG, etc. Even possible violations of unitary were first introduced in LQG and only recently in certain noncommutative geometries in brane theory. The absolute “success” of LQG over string M hype is brilliant.
One woud also remember that the number of researchers in string M-theory is of the order of 10 times that of LQG practitioners. Therefore, the relative “success” of LQG is still more impressive.
When Brian Greene claims, in public, that they can “see” GR in their equations whereas LQG have many problems for obtaining the correct macroscopic limit, he is being no sincere, because one may know first GR for introducing by hand the corresponding modifications on original string description for “convergence”.
Peter said:
“I do see some hope that if one better understands the structure of the standard model, one may be able to get to quantum gravity from there.”
I partially agree, but due to inconsistencies between GR and SM, at least one of both would be drastically modificated.
What if the failure of quantization of GR is on that GR is not correct after all?
Some question about this interesting possibility?
dan, string theory is not a quantum theory of gravity. Einstein gravity is 4D and nobody can derive that from 10D action without ad hoc assumptions. Moreover, string theory does not introduce an adequate quantum description of spacetime still. Non-commutative M-theory is just in a stopping way.
The description via gravitons is only “formal” with no macroscopic correspondence and for the unification with particle physics, in the words of Daniel Friedan (now a “renegade”):
“At best, for each macroscopic background spacetime in the manifold of possibilities, string theory gives large distance scattering amplitudes that form a caricature of the scattering amplitudes of the standard model of particle physics.”
Even if one see that the background may be chosen by hand previously.
mortain, after of several of my open criticisms to status of string theory, many people contacted with me, including previous string theorists. One of them, did a PhD in string theory and just leave the field (and physics) because insatisfction ith the way of high energy.
If instead of current dictatorial status in the field young people can research in other promising areas outside of string theory garbage, then several youngs promising physicists continue being today physicists and the high energy would today is full of new fascinating ideas.
You would be not angry if the “best”, “marvelous”, “fascinating” “theory” invented was simply a waste of time. You may be angry with Nature and its “stupid” choosing of a macro 4D without string or D0-branes.
If string theorists were no crackpot theorists and had not killed other interesting stuff…
If you play to Lotto and you put all your money in a single combination, you can win or you can lose. String theorists were completely sure of that they couldn’t lose, but the “Casino”, Nature, always win 🙂
But the culpable of failure of stringy endeavor is not Nature, nor Lotto, nor Peter, nor Glasgow, nor Phil, nor… nor this ignorant called Juan R. The problem was the arrogance of string theorists.
Peter, i think also that LQG is not the last word, still the research model chosed has been much more interesting. Supposed success of string theory, like the “derivation” of BH entropy, are also achieved in LQG with 4D.
If S is the ratio success/publicly for strings and L is for loops then L >> S.
After of many years working in silent, LQGs (especially Smolin) are now playing to publicy of their ideas, this is a deffences attitude against so many papers, talks, and popular books by “stringys” claiming that string theory is the only approach to quantum gravity, which is, sure, completely false.
Moreover, still LQG is open and would introduce interesting ideas for particle physics. Smolin thinks one could see by first time gravity modification to standard model on next generation of accelerators. Note that in LQG
E^2 = m^2 + p^2 + corrections terms
In regards to the anthropic principle, there is, unfortunately, a rather depressing prospect. All this nonsense, for all that Peter can throw around words like ‘unscientific’, ‘unpredictive’ and ‘unfalsifiable’, could still just be how the world is. We might just be stuck with it. There could be countless vacua, and we just might live in one of them for no particular reason.
If this is true then in terms of theories that make precise statements about the world in which we live, we are a lot worse off than we were in 1979. What perhaps many will fail to appreciate is that string theory is not a superset of our pre-string view based on quantum mechanics, QFT and GR, but an alternative. The ability to properly reproduce the “old” theories has never been demonstrated. So if this alternative fails to make testable predictions it is not a failure of physics in general, it is just the failure of a particular idea. It is arrogance of the highest order to conclude that the failure of string theory to predict means a failure of fundamental physics in general. We do, after all, have all the successful theories developed before string theory came on the scene.
Oh my. What a thread….
Certainly some people should be working on quantum gravity, especially if they are doing it in a non-overhyped way, trying to really seriously understand the technical issues involved. The LQG community appears to be doing this.
LQG is far from underhyped. They’ve had their full page spreads in the Times, Smolin gets quoted pretty much everywhere, and they’ve tiresomely put themselves forward as the great rebels against the overbearing and ignorant hordes of string theorists. Frankly, it’s just as offensive as anything that has ever come out of a string theorist’s mouth.
But that’s not really what I want to say. Judging from the comments, it looks like a lot of prospective physicists are reading this blog. I remember from not so way back when, as an undergraduate, in the days when Usenet mattered, I read sci.physics.research. What I didn’t know, then, was that it gave me a horribly skewed view of the field. When I showed up at graduate school, full of all the questions I thought string theorists had no answers for, I quickly discovered, sometimes to my embarrassment, that they knew all the questions and had good reasons for doing what they were doing.
So, hopefully without sounding horribly condescending, I just want to point out that Peter’s blog does not present a good idea about how things are. Now, I don’t want to lie: there is a sense of the doldrums in the field right now, especially after such a fruitful period as the nineties. Flux stabilization seems to have, much to the disappointment of many, led to an overabundance of vacua. This has led to a number of different proposals on how to deal with this, including anthropic arguments. It is not correct, however, to say that the field is consumed with this. The number of papers that deal with anthropic arguments do not even approach one half or one quarter. Most of us are perfectly happy to go on with our own projects and leave the anthropic stuff to the occasional dinner table argument.
My personal feeling on the subject is that trying to make predictions of the real world based on strings is like playing darts in a pitch black room without knowing which wall the dartboard lies on.
Now, Peter undoubtedly would think of that as a horrible indictment of string theory, but it isn’t. Even after 20 and more years, my feeling is that we do not understand string theory but that there is every indication that there is something there to understand. In the process of seeking that understanding, we have learned much about supersymmetry, nonperturbative gauge, the large-N limit, conformal field theory, gravity in higher dimensions, new scenarios for phenomenology and, not least of all, lots of cool mathematics. So, whatever mythical opportunity cost we may have incurred, I’d hardly say that these were years ill-spent.
Some argue, then, that there should be research alternatives. There are two answers to that. In terms of quantum gravity, there just aren’t that many games out there, and there’s not much market for the sort of speculation that could lead to a new direction — that sort of thing, much like the interpretation of quantum mechanics, should be left to the tenured. LQG is the most widely hyped alternative, but, their own PR aside, it is fraught with difficulties, not the least of which are the lack of a classical limit and a bizarre quantization procedure which, if applied to a theory like the standard model, gets physically incorrect answers. In addition, their claim to compute the black hole entropy relation appears to be quite ephemeral upon close examination. String theory, for all its ills, at least gets that correct. The simple fact of the matter is that no alternative theory of quantum gravity has come close to the success that string theory has had, however minor you may consider that success to be. If you think of yourself as a stubborn iconoclast, unwilling to follow the herd, realize that pretty much everyone who goes into physics is like that. It’s hard enough to get a group of physicists to decide where to go out to eat, much less browbeat them into a particular direction of research. There’s a reason so many people work on string theory, and it isn’t peer pressure.
But the second answer to the question is the more important, because it really belies much of the impression that one might get from this blog. The simple fact of the matter is that there are alternatives in high energy to working in strings, and those alternatives are more lucrative as career paths. As a commenter pointed out, LHC is turning on in a few years. This is the golden age of cosmology. Look at hiring patterns: people who do phenomenology or cosmology are being snapped up by the dozens. Lots of string theorists on the market are trying to rapidly broaden their horizons so they can compete for these jobs. So, go work on those things. That’s where the excitement is. There’s no need for string theory to ‘die’; there are plenty of other things to do with plenty of jobs to get.
And, why should it die, really? In regards to the anthropic principle, there is, unfortunately, a rather depressing prospect. All this nonsense, for all that Peter can throw around words like ‘unscientific’, ‘unpredictive’ and ‘unfalsifiable’, could still just be how the world is. We might just be stuck with it. There could be countless vacua, and we just might live in one of them for no particular reason. All the Poppers in the world can’t change that. But, it’s also possible that, as we understand the theory better and better, maybe some of those vacua fall away, or maybe we find universal predictions of the theory that apply for all physically realistic vacua. We’ll never know if we don’t try.
I’ve argued above that string theory has already had a string of successes even if the ultimate goal of a full theory of quantum gravity still lies beyond the horizon. Some people are antsy, to be sure, looking for things to say before the grand accelerator turns on, but, in my view, there are still many problems out there to explore. Once upon a time, in the late eighties and early nineties, people thought string theory was dying, too, but that was just the calm before the storm. Who’s to say that now is the time to give up, that, from here, all is hopeless?
Because, really, that’s just more hype.
Peter,
if I understand you correctly, you consider string theory interesting and worthwhile because of its connections with QFT dualities, but not as interesting as the hype around it suggests. This is a reasonable point of view which I share, to some extent. I agree that the potential of string theory to give us a unified theory of all interaction has been somewhat overhyped. This is not a unique situation: when people discovered N=8 supergravity, some suggested that it is the final theory of everything, without much evidence. The amount of hype in string theory is about normal and much less than in LQG, imho.
There are at least two reasons that so many people work on string theory (and not, say, on LQG). First, it is very rich and consequently fun. It leads to all kinds of neat theoretical ramifications which make one forget about the original goal (unification). The second reason is that it apparently does provide a consistent theory of quantum gravity, including black holes. No other approach to quantum gravity can boast this. It is true that the matter fields do not quite come out right, but this should not be very important. By studying string theory one has a chance to understand how to describe physics in a space whose metric is fluctuating. This is the point which Witten likes to emphasize, and it is also very reasonable. IMHO, these two factors account for the “unreasonable popularity” of string theory, not the hype.
First superstring revolution, second superstring revolution…..
my vote:
Categories and Logic revolution!
“Unless, of course, there is a revolution.”
Yeah! Let’s go!
Unless, of course, there is a revolution.
The first superstring revolution
The second superstring revolution
???
“Just die, string theory – please! Die, die, die! I’ve had enough!”
Unfortunately, history runs at a slower pace than a mere human would like! Many of us share your frustration…but I’m not holding my breath.
By the way, has anyone sorted out the relation between algebraic holography (Rehren duality) and the Maldecena duality yet?
Did someone come up with a generalization of the AdS/cft duality? Any quantum field theory, not just conformal ones?
It’s not really true that I’m not interested in either string theory or LQG. I’m interested in string theory as a possible way of solving QCD, as a source of interesting mathematical ideas, and potential techniques that might be useful elsewhere. I just think the idea of getting a unified theory out of a 10d string or 11d M-theory doesn’t work at all and people should recognize that and do other things.
I try and follow what is going on in LQG, also because I hope some of their techniques will be useful. The problem with quantum gravity is that you have no experimental guidance about what you should be looking for and no way to check whether your theory agrees with reality. Maybe this will change. But I’d be a lot more interested in quantum gravity if some way could be found to connect it to particle physics, where we have a huge amount of data. String theory hoped to do that, but it doesn’t work.
Certainly some people should be working on quantum gravity, especially if they are doing it in a non-overhyped way, trying to really seriously understand the technical issues involved. The LQG community appears to be doing this. But, personally, I don’t have any ideas about how to start from thinking about quantum gravity and get to particle physics, whereas I do see some hope that if one better understands the structure of the standard model, one may be able to get to quantum gravity from there.
What’s not healthy about the current situation is how much effort is being put into one research program, especially now that it has failed. People should be trying a wide range of different ideas, starting from what they know best and have good ideas about how to extend in new directions.
Sure, I think ultimately we’ll understand the correct relation of quantum theory and GR, but it’s impossible to know on what time scale. Right now though, the discouraging indications from both LQG and string theory are that if they produce a consistent theory of quantum gravity, it will be one that isn’t testable (Lee Smolin has some claims that contradict this) and doesn’t connect up usefully with particle physics. At the PITP conference, I think Shenker was claiming that, by holography, every QFT is also a theory of quantum gravity. If that’s true, you have a solution of the problem of quantizing gravity which is really a Pyrrhic victory.
Peter , you mentioned that you are not interested
in either string theory or Loop quantum gravity. My question is which approach according to you will lead to the correct quantum theory of gravity?
also do you support research in quantum gravity
(i.e. non-string approaches to QG)?
also do you think that one day we shall find the correct quantum theory of gravity?
mortain,
As another person planning on going into theoretical particle physics, I like to look at the positive aspects of the situation today. By the time I get a Phd the LHC will have been up and running for a year or two(still an undergrad right now) and if there are interesting observations I will be entering the field at very interesting time, and if there are no interesting observations it is still a good bet that many will stop working on string theory and there will still be a wealth of new ideas that should have been thought of by now to tinker with. Personally I am really glad I am entering the field now instead of say any other time in the past 20 years.
Hi Dan,
Sorry, but the idea of getting the structure of the standard model out of wormholes sounds like a complete pipe-dream to me.
The problem with perturbative string theory is that the loop expansion is divergent. So, while (conjecturally) you may be able to get finite answers for the contributions of n-loop superstring amplitudes to graviton scattering, you can’t sum the series. String theorists like to say this isn’t a problem, since the same thing happens in QFT where the perturbation series is only an asymptotic series. But, at least for non-abelian gauge theory QFTs, you have a well-defined non-perturbative definition of the theory, which seems to give finite results. Even conjecturally, the closest thing to this in string theory is something like Matrix theory, but that only works in some non-physical cases like flat 11d spacetime.
thanks for replying Peter,
yes i am well aware of lubos anti-lqg crusade, though he does come “out of the closet” and admits he’s spent “hundreds” of hours studying the subject.
john baez does hold out the hope that particles could be modeled on space-time wormholes through the fabric of space-time (as opposed to strings), though lqg is still in its infancy.
i am curious as to what you think of string theory as a quantum theory of gravity? string theory does allow calculations of s-matrix scattering for gravitons
I believe Veltman’s attitude towards string theory is much more negative than ‘t Hooft’s. See the last few sentences in his book about particle physics, explaining why he hasn’t mentioned string theory (or supersymmetry):
“They are figments of the theoretical imagination. To quote Pauli: they are not even wrong. They have no place here.”
Just die, string theory – please! Die, die, die! I’ve had enough!
My apologies for such an unscholarly outburst. [Please note my outburst is not aimed at string theorists.] After reading recent posts by Peter about how ludicrous string theory already is (and is becoming), particularly about what should be recognized as the death blow to the ‘landscape’, I just couldn’t contain myself. I agree with yourself, Peter, and always have. Juan R., I applaud you.
Damn string theory for being around at the time when I had hoped to begin a career in theoretical particle physics! Bad timing indeed; as if things, especially the availability of employment, weren’t difficult enough already in theoretical physics!
I think Unruh’s response to Susskind’s claim regarding string theory funding extends to every Western nation engaged in physics research… perhaps to every nation engaged in physics research worldwide, such is the prevalence of string theory and its hype. Wizened senior theoretical particle physicists: just keep on sapping that funding for string theory – only you know it makes sense!
By the way, Peter, do you know what ‘t Hooft’s former collaborator/supervisor, Veltman, thinks of string theory? I vaguely recall a post-lecture question about string theory being put to Veltman at a conference, but I cannot remember his answer (though I doubt it was as detailed as ‘t Hooft’s public remarks).
Also, Peter, why should string theory’s motivational ‘qualities’ concerning non-perturbative QFT be considered a success? String ‘theory’ seems to have motivated a lot of nonsense since its inception. As you point out, if more people had been working on non-perturbative QFT in the first place, and not on string theory, the progress already achieved to date would surely have been made, or made several times over, without the influence of string theory.
So… please, I beseech ye, just do the decent thing, string theory, and die. Forthwith, consign thyself to history!
Hi Dan,
I wasn’t thinking about LQG when writing about Lubos. He’s very much skeptical about it. My own opinion is that it’s a promising way of dealing with quantum gravity. But personally my main interest is not in quantum gravity, but in particle physics, and unfortunately LQG doesn’t seem to have anything to say about this.
A.,
I’ve followed ‘t Hooft’s public remarks about string theory carefully and corresponded about it with him. His own words should speak for themselves, but my interpretation of them is as follows:
1. He doesn’t believe that string theory based unification is anywhere near explaining anything about the standard model. He explicitly says he was a skeptic about this in 1985 and now feels he has been proven right. He refers to the need for a completely new idea in this area.
2. He’s interested in quantum gravity, and interested in what string theory has to say about that.
3. I think his words about dualities were carefully chosen. They have definitely led to interesting relations between QFTs and AdS/CFT is important progress towards finding a string dual of QCD, but precisely because ‘t Hooft has worked hard on large N, he’s aware of how limited this progress is. ‘t Hooft is also a careful worker, taking great pains to be very precise about what he is doing. I suspect the very hazy nature of a lot of the string theory duality stuff, and the lack of a fundamental understanding of what the theory is and where the dualities come from, bothers him.
As for the progress in QFT due to string theorists that you mention. Witten has certainly contributed a huge amount to understanding non-perturbative QFT, but most of this has had little or nothing to do with string theory. String theory has motivated some progress in non-perturbative QFT, and this remains the best reason to keep doing string theory. In this area it’s not a complete failure, like it is as an idea about unification. But I still think that if one-tenth the amount of work on string theory had gone into work on non-perturbative QFT itself, there would have been even more progress in this area.
CrisW says:
if Susskind’s conjecture was reformulated as “the Laws of Physics are determined by the requirement that the laws of physics are discoverable,” then I think it would stand a fighting chance of being fruitful,
Yep, I could buy it. Perhaps even “speakable” or “measurable” instead “discoverable”, which is very broad.
“How exactly are Laughlin’s “emergence” ideas very harmful to science in comparison to string theory, besides being a bit on the loony side?”
Homework exercise: write an essay for the Templeton Foundation explaining how Intelligent Design *is* after all scientific, once one takes into account the “emergent” nature of physical laws….[no money for this one I fear, because I bet that somebody has done it already…] Only in California. I hope.
String theory has its faults, but I have not seen a string theory paper anywhere near as downright kooky as Chapline’s Laughlin-inspired twaddle about black holes. True I have heard string theorists say some silly things about GR. But nothing on that level. The tone of Chapline’s stuff is frankly irrational: you pansies with your differential geometry — here, let me show you how a real condensed matter *man* handles a little problem like that!
By the way, I am impressed by Peter’s ability to divine Leonard Susskind’s emotional state by studying the bumps on LS’ bald pate. Technology updates phrenology.
That is, like said in 2003 and repeat to the beginnig of this 2005, string theory is a waste of time.
The basic equation i said in March 3, 2005
Arrogance + wrong physics + elementary math = fiasco
All supposed experimental indirect verification in acellerators, and cosmology (beatiful cosmic strings “explaining” dark matter), etc. all of that proven to be wrong.
The supposed predictive power of string theory and its “only parameter” diluyed in the fact of that Nature is, at least macroscopically, four dimensional. Nature may be stupid after all!
From the hypotetical TOE to the real TON “Theory of Nothing”
I said that string theory was not a scientific hypothesis.
Now many of string theorists agree with desesperatly claims as “physicists may have to rethink what it means for a theory to explain experimental data”. It sound somewhat as given that string theory does not agree with basic underpinnings of scientific method, we would change the method for adapting it to our nonscientific “Credo”
In recent years string leader Jim Gates like to use the term our “kind of a church”
Many string theorists have arrogantly ignored, furiously attacked (e.g. during decades claimed that LQG was wrong), or misunderstood other interesting approaches to quantum gravity.
On recent years Witten searched a link wth twistors, Vafa proposed that perhaps LQG (in past times a “heresy” for string theorists) could be a part of string theory, etc.
From the supposed leading of string theory durcing all of 20th century claimed in past years to the recent increasing number of canceling of lectures on the topic, halt publication of new undergraduate textbook on the topic; canceling of post-docs, summer programs, and conferences, etc.
Only five or six years ago, string theorists were claiming in public that the apparent 4D (“postulated” in standard model) was a consequence of string theory. What success!!
Recent work is less promising, as admited by Witten this year
“That’s a big problem that has to be explained. As of now, string theorists have no explanation of why there are three large dimensions as well as time, and the other dimensions are microscopic.”
Another of claims of string theorist was that string theory was the most fundamental and sophisticated theory newer imaginated. The math involved in string theory was imppresive and the concepts completely revolutionary ones.
We agree in that part of geometrical side of string theory is very advanced but in other parts string theory was always archaic, as stated from many people from many different fields: general relativity, advanced quantum mechanics, thermal fields, chaos, etc.
Even without experimental verification one already knew that, for instance, Schwartz superstring action was not the most fundamental approach to nature. But, and this is an very important point, string theorists have a general misunderstanding of that is being done in other fields of science. It is very arrogant claim that your theory is a TOE and explains ALL to most fundamental level, when you do not know equations, concepts used in other fields.
It is not so strange that one can obtain current string M-theory only after of many asumptions and simplications.
Fyodor,
How exactly are Laughlin’s “emergence” ideas very harmful to science in comparison to string theory, besides being a bit on the loony side?
If not many people are really taking Laughlin, Anderson, etc … seriously about their “emergence” ideas as a “unified field theory”, then how harmful are they? How much more “dangerous” are they compared to the crowds who follow quantum gravity in general?
Peter, it is very clear that the “emergence” bullshit being propagated by Laughlin and co is infinitely more harmful to the cause of science and reason than string theory could ever be. I suggest that you direct your ire in that direction. It’s obvious that this whole field is generated by the gargantuan chips that fools like Laughlin have on their shoulders because anything beyond special relativity is also beyond their comprehension. He and Anderson are living proof that even Nobel prizewinners can let their personal resentments overcome their professional judgement — indeed, in Laughlin’s case, their residuum of common sense.
Peter,
you say that ‘t Hooft’s positive remarks about string theory were “half-hearted”. I wonder how
you determined this. Perhaps this statement is simply a reflection of your anti-string bias. Why could ‘t Hooft not be genuinely excited about various dualities between gauge theories, or between gauge theory and string theory,
as in AdS/CFT? After all, he was the first to propose that in the large-N limit Yang-Mills theory
can be described in terms of strings. AdS/CFT makes this very concrete. (It also proves that superstrings are permanently part of theoretical physics, since they describe the strong-coupling limit of a very interesting QFT in 4d). String theory also enabled us to find or better understand many highly nontrivial dualities between QFT, by reducing them to geometric “dualities” or to the well-understood T-duality. Any QFT-lover would do well to study string theory.
I cannot resist noting that in the last 15 years there was a lot of progress in understanding nonperturbative QFT, and essentially all of it was achieved by people whom you would call “string theorists”, people like Witten, Seiberg, Vafa, etc.
..or to put it another way, such solutions look like simulations, based not on insight, but on sheer mathematical cleverness, with the promise that the results will ultimately justify the convoluted means. After all, Ptolemy’s account of celestial motions was of great practical use for centuries, and was overthrown by observations that were of little practical import but remained inexplicable in his system. Appearances might have been preserved with further refinement, but with explanation and not merely calculation as a goal, the effort began to seem pointless and futile.
Peter,
In the link you provided to lubos’ website, “the next superstring revolution” he does cite loop quantum gravity, which he admits he’s spent “hundreds of hours on” as a possible basis for another superstring revolution. so when you suggest none of these directions seems promising, do you also believe LQG is a dead-end? that would be surprising to me, as you have posted Lee Smolin’s responses to string theorists on several occassions
-Dan
At times one wonders whether something looking more and more like “spaghetti”, that something doesn’t look quite “right” about it. With more and more “epicycles” added in, it starts to look more and more like something that would impress Rube Goldberg.
If one has ever tried to figure out all of Enron’s accounting and obfuscation, it looks like the equivalent of “Rube Goldberg-ism” in the financial world. At times one wonders whether string theory, the old aether theory, and the many “unified field theories” over the years, are the scientific versions of “Rube Goldberg-ism”. Things look more and more complicated and more “spaghetti”-like.
See the Conclusion of this interesting new paper from John Stachel and Mihaela Iftime, posted on Friday.
Well, your blog is one of the most widely visited physics blogs. You definitely ARE having an effect.
I don’t know exactly what effect I’m having, but the increasing number of physicists willing to speak out about what is going on, and the increasing amount of skeptical press may be having some effect.
As far as the landscape goes, I think I’m in a solid majority, with even most string theorists thinking that it is not science. Recall that even Lubos Motl and I agree about this, and David Gross has spoken out forcefully and publicly on the topic. It was interesting to see that Susskind has started worrying that the NSF and DOE will start refusing to fund landscape studies. I suspect a sizable number of people on the panels evaluating particle theory grants may soon start (or have already started) giving low marks to proposals to do landscape research.
Is it possible that they are being so defensive because people like you are being so vocal in their dissent?
Regarding the last paragraph, if Susskind’s conjecture was reformulated as “the Laws of Physics are determined by the requirement that the laws of physics are discoverable,” then I think it would stand a fighting chance of being fruitful, although not by itself. Consider carefully what is implicit in the reformulated assertion.
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