According to a new article in New Scientist entitled The Theory of Everything: Are we nearly there yet? (unfortunately not available for free on-line), “The hunt for the theory of everything is turning into a road trip from hell – and don’t even ask who’s reading the map.” The article quotes Susskind and Weinberg as believing in the existence of a multiverse, even if this means that “all we can hope for from a final theory is a huge range of possibilities”.
Witten is referred to as a “string grandee”, and quoted as saying about string theory “More work has always given more possibilities – far more than anyone wanted… I hope that current discussion of the string landscape isn’t on the right track, but I have no convincing counter-arguments.” He’s welcome to my counter-arguments if he wants them: there’s not the slightest evidence for the landscape scenario pseudo-science, it’s incredibly ugly, not based on any kind of well-defined theory, explains nothing, and holds out no reasonable hope of ever explaining anything.
The article goes on to discuss the wishful thinking surrounding “M-theory”, quoting Witten as believing that M-theory may have a unique solution that fits our universe and explains the constants of the standard model. “Hope springs eternal” he says. Somebody seems to have given the writer the idea about M-theory that “theorists can prove that it exists as a mathematical construction, but they can’t actually write down its equations and there is no clear route towards doing so”, which is only true under a peculiar interpretation of the words “prove”, “exists”, and “it”. Lisa Randall is quoted as follows about M-theory: “We probably need fundamentally new principles… it’s not hopeless, but it’s going to require some deep new insight that we don’t really have.” She promotes her own work with Mukohyama on an alternate explanation of the cosmological constant.
The only person quoted in the article as thinking that there may be any problem at all with the way particle theory has been pursued for the last twenty years is Lee Smolin, who takes the absolute lack of any experimental evidence for string theory as a sign that the field may be off on the wrong track. He notes that “If you look back over the last 200 years, every decade or two there’s a dramatic advance, people always understand something new that couples theory and experiment… I suspect there is some right question that we’re not asking.”
Stephen,
I don’t understand your question very well. I don’t know if you are claiming for some fractal behavior.
In canonical gravitodynamics, gravitation depends of the scale with a parameter that is different for macro, astro, or cosmo scales.
I still don’t understand well that parameter but it appears compatible with certain cosmological requirements like expansion.
Unification will be no achieved by usual high-energy methods. Sure!!
My approach is not based in geometry or topology, just in AAAD.
Peter and Thomas,
Could it be that the critical mistake that is being made in the Unification theories is the assumption that gravity is not analogous to van der waals forces and is only representable at *all scales* as geometry/topology?
I am aware that Sakharov’s initial idea was fraught with problems, but is that sufficient to dismiss the entire class? I have reasons to think that current research in this direction is naive, cf: http://www.calphysics.org/articles/zpf_apj.pdf, but again my question remains.
Stephen wrote: How many more epicycles are going to be added to this theory before it collapses into some kind of Scholastic argument?
Might it be possible that a lot of money and brain power is being wasted on this theory that doesn’t seem to be able to make any measureable predictions?
Good questions! My personal guess is yes, a lot of time and research talent is being misdirected. To a large extent because leaders in the field have not been sufficiently frank and forthcoming. And then the hype—which distorts public and political support for science.
T. Larsson wrote: “…we could have seen e.g. a light Higgs, proton decay, muon g-2 deviation, permanent electric dipole moment, WIMPs, and probably many other things…”;
Would it not be more correct to write “should” instead of “could”. How many more epicycles are going to be added to this theory before it collapses into some kind of Scholastic argument?
Might it be possible that a lot of money and brain power is being wasted on this theory that doesn’t seem to be able to make any measureable predictions?
There are many potential signals of supersymmetry, some of which should already have been triggered. Apart from direct discovery of sparticles, we could have seen e.g. a light Higgs, proton decay, muon g-2 deviation, permanent electric dipole moment, WIMPs, and probably many other things that I don’t know about. An arxiv search for the keywords “tuning supersymmetry” gave 35 hits during the past year, the most recent one being hep-ph/0504246. Let me quote from the introduction
“Another problem comes from the fact that LEP II did not discover any superparticles or the Higgs boson. In most supersymmetric theories, this leads to severe fine-tuning of order a few percent to reproduce the correct scale for electroweak symmetry breaking. This problem is called the supersymmetric fine-tuning problem”.
I am no expert on SUSY phenomenology and never claimed to be. But if the experts say that there is a fine-tuning problem, I see no reason to doubt that.
It was, I believe, the need for SUSY fine-tuning that motivated the introduction of split supersymmetry. For almost 20 years, Witten used to say that string theory makes one prediction, supersymmetry (and one postdiction, gravity), but I haven’t heard him make this claim for a couple of years. One cannot help noting that string theory apparently stopped predicting SUSY once this claim became accessible to experimental tests.
SUSY requires fine tuning? Are you refering to the mu problem or the flavor changing neutral current problem?
Sure, there was a lot of work on unification before 1984, including work on GUTs going back to Georgi-Glashow in 1974. But this all involved pretty well-defined QFTs, so people could fairly quickly see if realistic models that predicted anything were possible. GUT models made predictions about proton decay that were falsifiable, and the models were falsified in relatively short order. Witten showed fairly quickly that supergravity Kaluza-Klein couldn’t produce a chiral spectrum (although now it has been revived as “M-theory” using singular compactification spaces).While Witten did a lot to promote supersymmetry, it was only one of many different research programs people were pursuing.
What changed in 1984 is that an overwhelmingly large number of people started working on string theory, abandoning and killing off many other research programs. String theory was and is so ill-defined that more than 20 years later no one can agree on what it is or extract any kind of prediction about it. This new phenomenon of the field being completely taken over by something this incoherent is what I had in mind in my remarks about how things changed in 1984.
Peter,
Unification was big business before 1984. The name was supergravity Kaluza-Klein. It became really big business when Witten got into it around 1978. That’s also when he introduced supersymmetry/supergravity in the USA. It was mainly a European thing till then.
This pessimism about string theory over the last year or two, seems to be quite different and more ominous than what happened during the temporary lull string theory experienced around 1990 (before D-branes, duality, AdS/CFT, etc …).
Another reason why the present situation is much worse than 1990 is that we know more now. In particular, we know that the cosmological constant is positive (so AdS is ruled out) and that supersymmetry requires fine-tuning at the percent level (which in some sense means that the odds that SUSY is realized in nature is down to the percent level). Since SUSY and a non-positive CC are the main soft-predictions of string theory, it seems rather problematic that both are ruled out by experiments. Not surprisingly, it is precisely these two results that have triggered the recent anthropic excuses.
Hence I disagree somewhat with the premise of this blog. I don’t think that string theory is not even wrong, but rather that it in fact is wrong.
hey she’s a fox
Hi
Peter and other interested folks,
you might want to look at this talk
“Can cosmology test Stringly physicis” by Hiranya Peiris and one of her collaborators
is Brian Greene
See http://www.stsci.edu/institute/center/information/streaming/archive/HubbleFellows2005/HubbleFellows2005Overview
Peter – nevertheless I thought it was interesting to get enough involved to see what was wrong. It was great fun to read all those papers.
-drl
I assume Peter doesn’t mean that to mean that you can’t challenge my statement.
… and don’t feel bad, Michael, Dirac apparently didn’ feel that he had need to consider that you have to condense Einstein’s static vacuum energy over a finite region of space in order to achieve positive matter density and pressure, or his hole theory might work a lot better… 😉
I’ve just deleted a bunch of comments from people insulting each other. Please stop doing this here and save me the time of having to delete these comments.
Lisa Randall… “promotes her own work with Mukohyama on an alternate explanation of the cosmological constant.”
lol
Einstein didn’ know that particle creation in his finite closed spherical near-flat positively curved static model, affects expansion.
“We probably need fundamentally new principles… it’s not hopeless, but it’s going to require some deep new insight that we don’t really have.”
-Lisa Randall
“I suspect there is some right question that we’re not asking.”
-Lee Smolin
“It never hurts to look in the basment”
-Danny Ross Lunsford
“I think it’ll be something that we’ve all missed.”
-John Baez
In the late eighties it was clear there were potentially a large number of possible string vacua, but they all had the problem of unfixed moduli parameters. So, one could hope that whatever mechanism was found to fix these would eliminate all but a small number of possibilities. More recent work such as KKLT seems to show that you can fix the moduli, but the mechanism for doing this just makes things much worse.
In the late eighties, string theory was very popular, but still pretty new. People didn’t have a huge amount invested in it, and if the 10^500 stabilized vacua had shown up then, quite possibly most would have been willing to abandon string theory altogther. Now you’ve got a whole field filled with people who have devoted either their whole careers or at least 20 years to working on string theory. What’s remarkable is how they show no willingness to admit failure in the face of utterly overwhelming evidence.
This pessimism about string theory over the last year or two, seems to be quite different and more ominous than what happened during the temporary lull string theory experienced around 1990 (before D-branes, duality, AdS/CFT, etc …). Despite the estimates of 10^100 possible Standard Model-like string vacuum states, nobody in the early 1990’s was really seriously talking about using the anthropic principle. This time around it seems to be the “serious” use of the anthropic principle in string theory, which has been producing more ominous signs of decline in the field.
Hi JC,
I don’t think it’s quite fair to label Einstein’s efforts to extend GR to a unified theory as “semi-crackpot”. They turned out not to work, but were not an unreasonable thing to work on, and he didn’t go around claiming any great success. Until 1984 there were always plenty of people running around doing various incoherent work for which they made grandiose claims about unifying everything, explaining the big bang, etc. But serious people pretty much just ignored them since they weren’t getting anywhere and there were plenty of more promising things to think about. The lack of any unexpected new experimental data, together with the lack of any good new theoretical ideas, is what has changed since 1984. Now the kind of pseudoscience that everyone used to scorn and ignore is being promoted by many of the most prominent people in the field.
Peter,
How common were persuits of “theories of everything” in physics, during the time period after Einstein died and before string theory? It seems like most of Einstein’s life at Princeton was largely in pursuing various semi-crackpot “unified field theory” ideas which ended up as failures.