Via David Goss and Lubos Motl, the news that CNN’s Candy Crowley has a piece about Witten. Unlike Lee Smolin’s
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Having mass means having a rest frame. In such a case the idea of “left” and “right” neutrinos disappears, and so any Lagrangian built only on (1+y5), which projects out the heretofore unphysical right-handed neutrinos, is going to be wrong. So I assume one adds in some terms in (1-y5) which go to zero with the neutrino mass. But then the mass has suffered from “scope creep”. It’s complicated.
i’ve wondered if neutrinos have mass, does this imply velocity can change if forces act on it?
“GUTS, both SUSY and non-SUSY, only achieve “unification” by introducing a whole new very problematic Higgs sector to break the new unification symmetries they introduce. This has never been very convincing.”
i am aware that GUT’s make predictions like proton decay that have not been verified. Do you think the strong nuclear force can be unified with the electro-weak force if you find the higgs sector to be unconvincing?
The situation with string M-theory is specially simple.
All, exactly all physics, predicted in the past by string theorists was wrong. This indicate, at least to me, the profound misunderstanding of nature that they have.
Initially, I studied string M-theory, including very recent material like stwing or non-commutative M(atrix) theory. All was wrong, and often the math involved simply ridiculous.
Seiberg-Witten paper in non-commutative geometry and string theory is very simplistic from a mathematical point of view (specially when one already worked with the non commutative star products in the phase space representation of quantum mechanics). Thus, I remained perplexed of the low level of string literature (when compared with popular claims on books and conferences). In many aspects, string theory is outdated. This is claimed in many published papers and conferences. For example, in the last conference Quantum future, Claus Kiefer and Erich Joos said
“this is even true for tentative frameworks such as GUT theories or superstring theory. Although the latter may seem ‘exotic’ in some of its aspects (containing D-branes, many spacetime dimensions, etc.), it is very traditional in the sense of the quantum theoretical formalism employed.”
Very traditional may be read “outdated” regarding, for instance, sophisticated experiments with fullerenes.
I am astonished that the self-proclamed ultra-advanced NC string theory (a radical modification of usual string theory in fixed background/cosmologies) used, in the last decade, advanced math developed in other fields of science by Prigogine and the Brussels School in the 60s. The delay of the “ultra advanced” theory is of most than 30 years for a supposed “profound” theory that, in the words of Brian Greene, is providing us the most basic understanding of nature! This is, obviously, false, simply propaganda.
The same situation arises in recent TFD Dp-brane theory. Today, string theorists are very excited with the new formalism (was unknown for them), but people that developed TFD in the past (were not string theorists) now are developing TFD II. Again, string M-theory is outdated.
What is correct in string theory (like a TOE)?
Simply nothing!! It is a waste of time.
Of course, the claim of that string theory quantizes gravity or predicts GR is false propaganda.
String theorists are well known due to their falsification of true. This is the reason of this blog.
For example, in his Elegant Universe, Brian Greene explained to many people that the observed 4D geometry of universe was explained from string considerations or that the concept of pointlike particles was substituted by the concept of strings, for example.
Curiously, he forgot to comment to public that string is an approximation and that the only known formulation of M-theory is a quantum mechanics of pointlike particles (D0-branes).
Ok, but can string theorists explain why universe look like 4D? According to Brian Greene popular book, that was explained by Brandenberger y Vafa.
To the question
– If these extra dimensions exist, does string theory offer any explanation of why there are apparently three space dimensions larger than the rest?
Witten recently replied
– 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.
There’s very strong evidence at least for neutrino oscillations, and I don’t think there’s any known way to explain this withough giving neutrinos mass.
The argument that the neutralino could be a dark matter candidate is the kind of thing that I had in mind in saying the arguments for supersymmetry are very weak. For one thing, you have no idea what the mass of a neutralino in these theories is, choosing it to solve the dark matter problem just looks to me like wishful thinking.
GUTS, both SUSY and non-SUSY, only achieve “unification” by introducing a whole new very problematic Higgs sector to break the new unification symmetries they introduce. This has never been very convincing.
thanks for answering some of my questions. as for SUSY, it’s been said the strongest candidate for cold dark matter is a SUSY-photon/higgs boson called the neuatralino.
the standard model does not yet unify electro-weak with the strong nuclear force, and most such unification scenarios predict proton decay and magentic monopoles. it’s my understanding that non-SUSY unification scenarios predict unobserved short half-lives of protons, so what is left is SUSY-unification scenarios of the standard model.
by the way, do you think neutrinos have rest mass?
Strange. Fourth order equaitions fill me with horror, although you can see how the string guys with a world tube have to deal with the sort of things ruled by 4th order equations in elasticity. So this must be why anyone would even consider it. Weyl’s theory in 4d died from 4th-orderness. Again, it’s like mangling some colossal Scrabble Lagrangian so that it churns up something resembling QED.
R^2 theories do have fourth-order equations of motion in the metric variables, thus problems with unitarity and causality. Some people (e.g. Hawking) at times have claimed that maybe these can be dealt with. More positively, these theories are renormalizable.
All known approaches to quantum gravity have one problem or other.
The standard model isn’t a theory of everything, in particular it isn’t a theory of cosmology. It’s a theory of what particles and fields there are and how they interact (excluding gravity). As for the specific questions you ask:
matter/antimatter asymmetry: where this came from is a cosmological question. In conventional cosmological models, you can take advantage of various features of the standard model (CP violation, electro-weak symmetry breaking) to get mechanisms that produce this asymmetry. Whether within such cosmological models these mechanisms are sufficient to produce the observed amount of asymmetry I believe is still an open question.
particle masses: this is perhaps the main weakness of the standard model. You have to put these numbers in by hand, whereas you would like the theory to predict them.
magnetic monopoles: there are no stable, finite energy magnetic monopoles in the standard model. This agrees perfectly well with the fact that they aren’t observed.
dark matter: again this is a question of cosmology and astrophysics. There is no particle in the standard model whose abundance in standard cosmological models would explain what dark matter is. Maybe there’s a new particle not known to the standard model, maybe something else is causing this.
dark energy: you can set the vacuum energy to whatever you want in the standard model, including the observed cosmological value. The vacuum energy has the same status as particle masses in the standard model, it’s an undetermined parameter.
SUSY: there’s no good reason to extend the standard model to a supersymmetric version. The positive arguments about what this buys you are weak, and supersymmetric models are much more complicated, have a hundred or more extra undetemined parameters, and a host of other problems.
Peter, when you speak of the standard model working so well, how does it explain the matter/antimatter asymetry? does it predict masses? why are there no magnetic monopoles? what is dark matter? what is dark energy? do you think the standard model needs to incorporate SUSY?
Peter, what are R^2 theories? Aren’t those fourth order in some context (and so loaded with unphysical solutions)?
“This said, String Theory in it’s various forms and sects is a very useful theoretical tool,”
I’ll ask the question on everyone’s mind:
Useful for what?
Is it true that the LHC (Large Hadron Collider) will be used to find the super-symmetric particles that string theory has proposed?
A little background about me: I am a physics graduate in Hong Kong. String thoery appears too profound to me. But I am interested in its latest development.
Do String theories contribute? Yes. Isn’t that enough?
No it isn’t, and if I had known 25 years ago that the majority of particle “physicists” were apt to go on this quasi-religious quest just because Ed Witten told them to, I would have gone into molecular biology instead.
There is no, repeat, no experimental evidence to support string theory or even to suggest that it might be a promising idea.
I had to knock on wood to ward off the bad mojo that comes from slandering Newton! When it came to understanding the universe Newton was wise enough to defer to “angels” as a viable force when pressed;)
This said, String Theory in it’s various forms and sects is a very useful theoretical tool, and I think those who’d pooh pooh them for their inability to be all things to all people are missing the point. There’s an infinite variety of ways to view collections of data gathered across the spectrum of experimental apparatus, but there’s very few ways to accurately identify generally observed trends for future practical refinement and advance of our total body of scientific understanding. Do String theories contribute? Yes. Isn’t that enough?
Penrose seems to think highly of something called Twistor Theory.
This is a bit like saying “the pope seems to think highly of a religion called Catholicism”.
No, I don’t want to elaborate on this. There have already been long discussions about this here, see for instance Lee Smolin’s response I posted on June 15, 2005, as well as his exchange here with Larry Yaffe (August 19 and August 22, 2004).
In general my impression is that neither LQG nor string theory has yet given a completely satisfactory theory of quantum gravity. But the LQG program tends to work with well-defined concepts so you can at least see exactly what their problems are, whereas the string theory arguments often involve very ill-defined concepts and loads of wishful thinking.
“…although arguably at least one of them (LQG) does a better job of it than string theory…”
Can you elaborate on the ways you think that this is true?
Hi Pseudo String Fan,
Your question is one I was asking myself two months ago. I’m not a scientist, just an interested layperson. The thing that helped me grasp some of the issues involved was reading Roger Penrose’s chapters on String Theory in his book “Road to Reality.” He deals with some of the difficulties with grand unification, and while I can’t pretend I understood every word I did digest enough to recognize that there’s more to the story than we get from a book like Michio Kaku’s “Parallel Worlds.” For me at least it was a real wake up call.
Penrose seems to think highly of something called Twistor Theory. He also includes a chapter on Loop Quantum Gravity and other potential avenues of pursuit.
Hi pseudo string fan,
Despite what you might hear in some places, string theory doesn’t actually now provide a consistent unification of quantum theory and gravity. The string perturbation series is divergent and no one knows what non-perturbative theory it is supposedly asymptotic to.
There are quite a few other attempts to unify quantum theory and gravity, none of them completely satisfactory, although arguably at least one of them (LQG) does a better job of it than string theory. Some of them are:
1. Loop quantum gravity
2. R^2 theories
3. “Induced gravity”
4. Various versions of triangulated or lattice gravity
5. Topological quantum gravity
and there are probably others…
I voted yes on the CNN poll. Modulo the standard caveats about what one means by a “theory of everything”, I do believe that sooner or later we’ll have a theory that ties up the remaining loose ends of the standard model. Personally I think the fact that the standard model works so well means we’re actually rather close to what Weinberg calls a “final theory”. We might even be there now if so much of the effort of the last twenty years hadn’t been wasted…
If you don’t do string theory, with what theories can you bring general relativity and quantum mechanics together?
I just wish Michio Kaku would calm down a bit.
So Peter, did you participate in the poll on the CNN web page?
String theory is, in the words of its more popular practitioners, the Final Theory: the Last True.
It was not designed like a dual representation of QCD, like an attempt to perturbatively quantize gravity alone or like a generator of mathematical ideas, it was studied, extended, thought in some High Schools, and popularized to public like the Final theory: the Theory Of Everything.
String theory is wrong; it has failed for explaining everything. It has failed for quantize gravity (perturbative series is not well defined and nonperturbative regime is unknown), it cannot explain GR (contrary to popular Witten claims string theory does not predict gravity, really string theory is adapted to previously known gravity), etc.
I partially agree with the idea of Witten like a new Einstein. Of course, the contribution of Witten to physics is irrelevant (Murray Gell-Mann advanced physics 10 times more than Witten). But I agree in that the emphasis of Witten on “his” string theory sound like the emphasis of Einstein in his unified field theory. Einstein didn’t understand other best theories developed in his time and Witten is doing the same error now.
String, stwing, M-theory, and all that stuff are a waste of time. Since that their research is based in irrelevant mathematical formalisms and outdated concepts. String M-theorists (here and thereafter SMt) are so arrogant that with a superfitial mathematical knowledge of other fields of science, they claim for a Theory Of Everything. The list of outdated concepts and irrelevant mathematical formalisms is greater than number of estimated vacua (-:
– Usual quantization of the classical bosonic string violates cosmological boundaries. (I wait that SMts will recognize this error before 2050 :-).
– The spacetime used (CY, G2, etc.) do not account for the non-differential character of stochastic processes. It will be funny like string theorists will attempt to model spacetime-foam noisy contributions to a triple D0-brane collision. I wait to see his faces then!
– In the usual unitary vectors space of string mathematics the L-product of two elements is not defined. Only in the L-space the relation I+(rs)I+(tu) = I+(ru)delta(st) is defined. No similar product relation exists in the H-space (dimension n) because L-space (dimension nn) is more general. That is, the supposed TOE cannot explain, for instance, Ernst’s work in NMR (that received the Nobel prize) đź™‚
– The fixed background S-matrix is, undoubtedly, a funny caricature of real-word processes. There are dozens of well-known papers on the topic and even a new branch of string theory developed!
– Vector states used in the standard spectral decomposition of strings (branes) are of course valid only in the limit T –> 0. This was known for decades in other fields of science like plasma physics (quark-gluon plasma). Only the last 5 years, after of three decades of totally wrong research and funny claims, SMts fixed this sound error and developed the very recent Dp-branes theory with the (~) operators, which only work in the linear regime. Far from eq. one cannot use the tilde (~) operators due to well-known presence of dynamical bubbles coupling spacetime events. Of course, all this advanced mathematical stuff was/is ignored by leading researchers like Witten, Greene, Vafa, Schwartz, etc. Witten, the great genius, the great theoretician, the new “Einstein”, did NONE contribution to recent doubled space Dp-branes theory. In fact, his great mind did not know the problem with the use of standard states because he like other string theorists study the topics just superficially. He is a great string theorist sure đź™‚
– String theorists still claim for the derivation of an unitary theory, whereas people in other experimentally proved theories are working with LPS theory in Gelfand triplets. The theorems used are outside of the simple and outdated string mathematics, and one needs a lot of recent mathematical work in rigged spaces and involutive Banach algebra of bounded operators. These non C*-algebras are, of course, ignored by SMTs and their irrelevant TOE. It is impossible to explain recent models for neutral Kaons and its counterparts in higher-flavor-generations from the basic mathematical framework of string, M theory. Concretely the models developed in the last decade by Sudarshan (e.g. generalizing the LOY model) does not fit to string M-theory because are more general.
– Non-critical string theory is more advanced that usual critical (Witten-Schwartz-Vafa-Greene-etc.) one in fixed backgrounds but again irrelevant for a TOE. The most advanced formulation today in non-critical theory simply use “Lindblad–like” operators (which is only valid if one take the zero limit of the correlation functions for the different vacua) to take into account quantum transitions between different critical string vacua. Moreover, the non-critical string theory has unsolved problems. One can show (with the aid of mathematical methods unknown for SMts and still don’t applied to noncritical formulation) that non-critical string theory formulation is just a shadow to more consistent and generalized theories.
M-theory is “the best candidate for a theory of everything“, sound like that old claim of “all universe is understood from Newton mechanics“.
All of us know how accurate was the claim đź™‚
String theory is wrong because it utterly fails inside its context. Likewise, Weyl’s theory is a total failure, notwithstanding Weyl 1929 where phase is made the cuckold of gauge (see O’Rafairtaigh). Failure in physics means insufficiency to the expected context. On this level, string theory is an absolute failure.
Not sure what your simple SPIRES search is, but looking at the SPIRES list of most heavily cited papers in 2004, the top 5 string theory ones are
1. Maldacena on AdS/CFT 446 citations
2. Witten on AdS/CFT 258 citations
3. Seiberg-Witten on non-commutative geometry and string theory 231 citations
4. Gubser, Klebanov and Polyakov on Ads/CFT 225 citations
5. KKLT paper 190 citations
Only 5. has anything directly to do with getting a unified theory out of string theory. We can argue about what use 3 is, but 1, 2, and 4, are about AdS/CFT, an explicit relationship between a 4d QFT closely related to QCD and a 5d string theory dual to it, something which has nothing to so with string theory as a unified theory.
“It quite possibly can provide some sort of dual description of QCD, and that is what much research in string theory these days is aiming for.”
By much I guess you mean about four percent, as a simple SPIRES search can verify?