Over at the new Cosmic Variance blog, Sean Carroll has posted a defense of string theory against what he sees as disdain, resentment and disparaging remarks from other physicists, a defense he entitles Two Cheers for String Theory. I’ve written a couple of comments over there, and maybe this will lead to an interesting discussion. But I’ll be traveling a lot of the time during the next week and a half, so my ability to participate in such a discussion, here or over there, may sometimes be limited. We’ll see what happens….

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Wolfgang,

I am not talking about conventional anomalies proportional to the third Casimir, which indeed are inconsistent – the anomalous algebra does not possess any unitary lowest-weight reps. If you introduce the observer’s trajectory and quantize it together with the fields, there are also new anomalies proportional to the second Casimir. This is necessary to do canonical quantization in a manifestly covariant way, see hep-th/0501043.

It should be possible to describe these new anomalies also in the conventional, non-covariant Hamiltonian formalism, although I have not thought so much about it. The YM gauge algebra can be cast in the form

[J^a(m_0,m_i),J^b(n_0,n_i)]

= f^abc J^c(m_0+n_0,m_i+n_i)

+ k \delta^ab m_0 \delta(m_0+n_0)\delta(m_i+n_i),

where four-momentum m = (m_0,m_i) has been split into temporal and spatial components. The extension can be expressed covariantly, but this form is suitable to make my point. Note that this is a 4D generalization of the affine algebra, and it is easy to show that it is indeed a Lie algebra.

The spatial subalgebra, generated by J^a(0,m_i), is anomaly free. This means that you can construct the Hilbert space as usual, and mod out spatial gauges. However, a rarely observed fact is that the temporal gauges are implemented as time-dependent canonical transformations. If the extension is non-zero, you will run into serious trouble with this.

This does not happen for the free Maxwell field, because the adjoint rep of U(1) is trivial. But it does happen in interacting theories, where the second Casimir k != 0. I do not understand this in detail, because I have only quantized interacting theories in a formal sense, but it must be related to renormalization.

Anyway, the second-Casimir extension is simply there, and it always arises when you build lowest-energy reps of the gauge algebra, see math-ph/9810003.

I have been reading this review of string theory, very complete including susy, D=26, D=10 etc…

J. Scherk An introduction to…

http://prola.aps.org/abstract/RMP/v47/i1/p123_1?

Now I think about, they missed the opportunity to stab the muon as a susy partner of the pion.

Hi Thomas,

I did not say nor imply that anomalous local gauge theories would

be consistent, rather that you’d be warmly invited to try to prove this ðŸ˜‰

In fact, it is standard knowledge that it is not possible; unitarity

will be lost (and renormalizabilty: the anomalous graphs scale not

in the way the non-anomalous ones do, and there is no renormalization

scheme where you could cancel the divergences of both types of graphs

simultaneously).

If nature is any guidance: the spectrum of the standard model is

supposed to be anomaly free, and this had in the past led to the

prediction that given the tau lepton there should be a bottom quark

(and similarly a top quark given the tau neutrino). This prediction

has been experimentally verified later, and one may view this as a

spectacular triumph where theory made a prediction based on

consistency, ahead of experimental data.

Summa summarum, I don’t see why one would insist on abandonding

gauge invariance and giving up consistency for no good reasons.

As for gravity, things may be more subtle and it looks indeed that

background (in-)dependence may have something deep to do with

anomalies. In topological strings there is a beautiful story relating

certain anomalies to an apparent background dependence, and this

could be a prototype for something more general; there are some

recent, extremely interesting papers on that. However, the involved

“holomorphic” anomalies are not crucial for the consistency of the

theory, so there is no parallel to local gauge symmetry; rather, it is

more the other way around, namely the holomorphic anomalies arise

_because_ one insists on a consistent geometric interpretation of

the theory.

Wolfgang,

I thought we agreed that gauge anomalies cannot in general be dismissed on the grounds of unitarity violation – the subcritical free string. The chiral Schwinger model in 2D is another example, at least according to Roman Jackiw. As for 4D gravity, here is what I have and have not done.

I don’t see how to use path integrals, so I prefer a version of canonical quantization which is more directly connected to representation theory. But any correct quantization method should do.

Moreover, I don’t know how to prove unitarity, because I don’t know what the invariant inner product is. But I do know that every non-trivial, unitary rep of the diffeomorphism algebra must be anomalous (in 1D, c=0 implies h=0), and I know how construct anomalous reps. So at least I satisfy a necessary condition.

The problem, both for path integrals and unitarity, is this: In order to avoid infinities, I must first expand all fields in a Taylor series around the trajectory q(t), and truncate at some finite order p. This gives me a classical, non-linear realization on finitely many fields of a single variable, which is exactly when the normal-ordering prescription works. Without this step, normal ordering gives infinities and diffeomorphisms do not act in a meaningful way.

Thus everything is expressed in terms of Taylor data instead of field data. Classically, this is nothing, but I don’t see how to make sense of a path integral over Taylor data. And although one can readily write down inner products, I haven’t found an invariant one. Another problem is that truncation to order p is a regularization, which must be removed at the end. Infinities resurface in this limit, and can only be cancelled with a clever choice of field content.

I don’t claim to have quantized gravity. However, I have quantized (on a linear space rather than a Hilbert space) a regularized form of gravity, while maintaining manifest diffeomorphism covariance, constructed the relevant anomalies, and derived conditions when the regularization can be removed. I think that that is a rather significant achievement, in particular since there is no abundance of good new ideas around.

Thanks Quantoken,

I contacted with Eotvos group and are waiting for reply.

I cannot “rebate” your arguments now, since that i discover this posible weakness of Newtonian potential today.

However, let me say that like in some well-known LED models (e.g. mm-scale string extradimensions), perhaps the reduction of dimensionality could be undetected with usual non-gravitational thecniques being real.

Thomas,

the issue of background independence in QG is a subtle one and I

prefer not to get drawn into this. But as far as local gauge anomalies

are concerned, I wouldn’t see how an anomalous theory would make

sense from a path integral point of view. And I would expect important

basic properties like unitary getting violated – so in order to be

convincing, why don’t you cook up a proof that anomalous gauge

theories are unitary, that would help your case !

Juan said:

“Basically the idea is as follow if recent sugestion of experimental verification of weakenes of Newton force to short scales is correct. This would be a final knock to String M theory.”

Not to defend the string M theory, but it should be clear that the “recent experimental verification” of weaker gravity force at shorter distance is very weak in credibility, and does not say anything either way. Further, it has

nothing to do with reduction of dimentionality, even if the reduction of force is credible and verifiable. Clearly the distance scale at which the allerged force reduction happens is well above atomic scale, and we have plenty of solid evidence that at atomic scale everything is just as 4-D as the macroscopic scale. Should dimentions start to reduce, which could be possible, it should start at a much much smaller scale.Quantoken

Recent post in cosmic variance

Basically the idea is as follow if recent sugestion of experimental verification of weakenes of Newton force to short scales is correct. This would be a final knock to String M theory.

Ignoring possible dependence on relative velocity, one obtains strong effective gravitational interaction to shorter distances, I take like good the rule 1/r^(2+d) for d extra dimensions (some recent RS brane model introduces Yukawa like exponential correction from extra 5th dimension), we can observe that smooth behavior is obtained formally with

d 0 imply formally elimination of divergencies on (1/r^2) force strengh since (1/r^2) —-> (1/r^0) at short scales without appeal to an arbitrary (by hand) add cut-off.

Are not these exciting news?Wolfgang,

Although people know that subcritical strings are fine, they still seem to believe that gauge anomalies are inconsistent, and that gauge symmetries are redundancies of the description. Lubos has repeated that phrase for five years. Moreover, in a discussion a long time ago, Jacques Distler implied that there is a fundamental difference between conformal gauge symmetries, relevant in string theory, and conformal global symmetries, relevant to 2D critical phenomena. Why would he do that if he realized that gauge symmetries can become global upon quantization?

So one thing I want to do is to eliminate the widespread myth that all gauge anomalies are inconsistent and must be cancelled.

This issue comes up in the context of diffeomorphism symmetry in QG. It was always obvious to me that the diffeomorphism group will acquire anomalies in 4D QG, which is pretty obvious since already 2D QG has gauge anomalies. (The anomaly can be traded between the Weyl and diff sectors, but it can not be removed.) With this is mind, I generalized the Virasoro algebra to higher dimensions (in particular 4D), and worked out its Fock representations. Fortunately, the same problem was simultaneously addressed by mathematicians Rao and Moody (of Kac-Moody fame), which helped me overcome the crucial obstacles.

In case you think that there are no pure gravitational anomalies in 4D, it is only true if you quantize the fields alone. A crucial insight is that one must also explicitly specify where observation takes place, and quantize the observer’s trajectory together with the fields. This is mandatory because the relevant Virasoro-like cocycles are functionals of this trajectory.

One can view the controversy between ST and LQG in the light of this result. The key lesson of GR is background independence, and the key lesson of QM is that it is QM, in the Fock sense. However, Lee Smolin has informed me that a rigorous theorem rules out anomaly-free Fock quantization of background-independent theories, and I see no reason to doubt that assertion, partly because I have proven similar (but very non-rigorous) theorems myself. Locally, this leaves three possibilities:

1. QG is not background independent. A lot of people would dislike this possibility, because it would violate the spirit of GR, but it is a logical possibility.

2. One should not quantize in the Fock sense, but only in the weaker LQG sense. A lot of people would certainly dislike this, especially the part of the unbounded harmonic oscillator spectrum.

3. The diffeomorphism symmetry is anomalous. This neither violates the spirit of QM nor GR, it is known to happen in 2D, and much of the math is now here. However, the anti-gauge-anomaly myth prevents this idea from being taken seriously.

Thomas,

that strings with c less than 26 are fine and make sense is known since a long time, there are hundreds of papers (I guessimate) on this issue called non-critical strings. This includes the well-investigated c=1 model, etc. What is what you want to convey – that professional physicists wouldn’t know about this ?

As for desinformation, it is one of the unfortunate virtues the internet has brought to us, namely that laymen can just go ahead and spread nonsense, and other laymen are sadly influenced by this as they have no way to distinguish crap from serious science. This is what I meant when I was referring Q’s statements, in relation to someone expressing appreciation for them.

Wolfgang,

The most notorious desinformation spreaders are those highly educated people who claim that a gauge symmetry necessarily is a redundancy of the description, despite the fact that 2D gravity coupled to D < 26 scalar fields is neither inconsistent nor anomaly free. It has taken me a long time to reeducate Lubos, but now I think that he finally understands this point.

It is not surprising that quantizing 4D gravity fails if you don’t know about the relevant diff anomalies.

“Quantoken,

Thank you for the explanation; much appreciated. That would be a bitter disappointment if the LHC were not to get up and running.

”

Indeed. Fortunately I see many thousands of highly educated people around here working hard to make sure it will work. They know what they are doing, in contrast to those notorious desinformation spreaders who have not the faintest clue of what they talk about and who would still live in caves if all of mankind would think like them.

Mike CrowleysaidPlease forgive my ignorance, but I was recently watching a lecture for non-scientists on particle physics that seemed to suggest that the discovery of super-partners for the elementary particles might be a validation of string theory, and that this is something potentially achievable at labs like CERN and FERMILAB. Is this a misunderstanding?Well, personally i suspect that supersimmetry will be not observed (as already suceeded in the past).

Supersimetry is not a prediction of String theory. It is a requirement put by hand for admending tachionic behavior (experimentally unobserved). The observation of supersimmetry will be not a verification of ST.

Moreover, ST predicts exact supersimmetry and if observed in a future experiment we will observe only high-energy supersimetry behavior, but still low-energy non supersimetric one. ST

failsto provide a mechanism for the observed low energy behavior and, therefore, is incorrect.Hi Peter,

“you can’t reliably calculate anything at generic values of the moduli and couplings”

That’s what I said when I wrote that it’s hard to compute things in the middle of moduli space absent a more unified definition of string/M-theory. But it’s not so terribly discomforting as you claim. Certain points in moduli space can be shown to have low-energy limits which are exoctic things like E_8 gauge theory or massless “gauge strings”. We have no idea how to right down an effective Lagrangian in such cases. On the other hand, in the string theory, many things remain computable in principle. If string theory is worth nothing because it can’t give better answers to these questions yet, then QFT is even worse off. We would have never even known that we *should* be able to make sense of things like E_8 gauge theory. Understanding this means realizing that it would be more than amazing if we had been able to understand all of the moduli space from the out start.

But we’re getting there…

Quantoken,

Thank you for the explanation; much appreciated. That would be a bitter disappointment if the LHC were not to get up and running. I remember how disappointing it was when the Superconducting SuperCollider project was canned–it would probably be operational by now.

Michael,

No, you don’t have a “good non-perturbative formulation” and you can’t reliably calculate anything at generic values of the moduli and couplings. If you look at the discussion over at cosmicvariance you’ll see the professional string theorists admitting this. You’ll also note that they and Sean agree with my intial point that you found so ignorant. As Sean points out, one way of seeing that non-perturbative string theory may have amplitudes that look like field theory ones, not stringy ones, is just to look at the 11d supergravity corner of the conjectured moduli space for M-theory.

I’m kind of charmed at the idea that I’m bullying the likes of Jacques Distler, Lubos Motl, or other serious string theorists. But you should know a lot about bullying,since you seem to think the way to deal with someone who makes serious arguments that threaten your beliefs is not to answer them but to personally insult and attack the person making the arguments.

Peter,

The suspenders holding up my pants broke and I had to use a *string* to tie them back up.

Microly said: “….a theorist saying that the worst thing that could happen in particle physics at higher energies would be to discovery “only” the Higgs.”

That’s because the Higgs particle is the only missing piece of the standard model that has yet to be confirmed by experiments. People wants to go beyond the standard model so they need some clue by finding something that the standard model failed to predict. If Higgs and only Higgs is found, then the picture of standard model is complete but they still can not move beyond it, so that’s the worst of possible outcomes.

The problem is nobody said anything specific about how these supposed super partners look like. Certainly that’s true for Higgs particle or Higgs particles as well. If you can’t tell specific details you can’t really say you have predicted something. They know absolutely nothing about the allerged new particles they expect to discover, except for the names. So you bet they have prepared a bunch of printed labels so anything that jump out of LHC will be automatically assigned a label and be claimed as something they predicted beforehand.

I predict that the most likely outcome of LHC is it be killed before producing anything useful, either because

1.it run far over budget, or because

2. they fail to achieve the design specifics, or

3. everything work as expected but still no new discoveries except for maybe a couple of high energy resonance states of known particles.

Quantoken

One other quick question: I remember reading a quote from a theorist saying that the worst thing that could happen in particle physics at higher energies would be to discovery “only” the Higgs. Is this related to the super-partner search? This comment bewildered me, because I came away from these lectures thinking that the discovey of the Higgs would be an important triumph.

I really appreciate this discussion that has been going on across several blogs, and appreciate also entries like this that take into account that laypersons are interested in this difficult topic as well.

Please forgive my ignorance, but I was recently watching a lecture for non-scientists on particle physics that seemed to suggest that the discovery of super-partners for the elementary particles might be a validation of string theory, and that this is something potentially achievable at labs like CERN and FERMILAB. Is this a misunderstanding?

Thanks!

Lubos has written a reply to Sean article in his own blog.

Curiously, he agrees with me on that the article is outdated and shows very wrong ideas about real status of string theory. As said in several occasions, research ST is not the same that layman version of ST.

My several years claim of that string theory is a theory without strings and the name is maintained by marketing purposes are supported by Lubos now.

Michael below:

Do you realize that your response below had NOT disputed a single point Peter raised. If any thing you enhanced Peter’s arguments where ever you can. You seem to be pretty weak in logical skills and must look quite dumb if been spotted walking on the street.

I especially like this:

Peter said to Michael:

“You seem very proud of knowing what is in the first chapter of Polchinski, but

do you know anything else about physics.”I would have removed the unnecessary word “else” above. Michael may have wasted decades training himself in being able to recite the whole book of Polchinski in reverse order without a mistake, but he surely had NOT picked up any idea what is science and what physics is all about. Physics is all about being able to explain and predict observables. Not a single thing in Polchinski book, or any other super string theory stuff has proven itself relevant to anything in nature.

You may continue to wish that there will be more super string revolutions to come. But over 2 decades of research so far yields absolutely nothing that is valuable, and can be summed up in one word “failure”. In light of that, any wish that the situation could change in the near future, can only be described as wishful wishes.

I think some one must have got to be incredibly stupid to be so willing to plunge his/her intelligent lifetime into such a hopeless pursuit, like dropping a stone into water, knowing full well how fruitless this could be. While people pursuing some other un-explored ideas may probably be gambling for success, SSTers can only be described as suicidal.

People like Edward Witten must have an IQ far exceeding Einstein. But I view them as Einstein’s wasted because they are pursuing the wrong path. As I said already if the nature is not co-operating and is not 10-D, then not even god can create a 10-D theory to describe a none 10-D universe, unless it’s either a wrong or an useless theory.

Michael, thousands of much more qualified researchers before you have wasted a collective one thousand intelligent lifetimes without figuring out something useful. What makes you think you are any different from them, in terms of luck? Or you consider this whole enterprise as just a job to earn livelihood? Then there are much easier ways to do it.

Quantoken

Some analogy:

String = WMD

String Theory = War in Iraq

String Theorists = NeoCon

Michaels:

“What I dislike is pretenders.”

I understand the general feeling. This time you didn’t drag in bystanders into that sentiment by falsehood.

Thomas:

“I don’t think that neither you nor Michael grasped the discussion over at Lubos’ blog.”

It is correct that I do not grasp the technical part. What I meant was probably correct was when Michael accused you of bringing up a seemingly detail as “the most important lesson of string theory” as trying to seem important.

Now you have explained your inspiration in a much different light. I am sorry if I hurt your feelings.

Nigel:

“Torbjorn – please realise it is personal when the rejection is made because I am not contributing to mainstream string speculation.”

I sincerely does not understand your thinking. If you had contributed ‘to mainstream’ you had not been rejected, you say so yourself. There is absolutely nothing personal (about you as a person) in that.

Maybe you mean that you take it personally? As per above reasoning you should not.

I add my reply to Sean here

Dear Sean, the problem with current unpleasant status of string theory into the community was built by own string theory community. Let me first remember to you some basic points –the list, of course, is not exhaustive–, which will help to you to rewrite your “cheers”.

– String theory did born like a failure to explain strong force and since it has been always a complete failure. Nothing predicted and all past claims shown to be false. String theory is a theory without laws or postulates because they are modified with time. Please, let me remember to you the history of dimensions: 4D -> 5D -> 26D -> 10D -> 11D -> 12D (some people is working in more than a time dimension) -> 4D (Segal has claimed that we may find a 4D version for solving compactification problems), etc. The claim of string theory is “open” is, of course, a complete nonsense when claim is properly interpreted on both epistemological and ontological terms.

– It is well known that string theorists have manipulated public opinion about string theory. In fact, no popular string theory writer has still convincingly explained to public that string theory failed like a TOE since is being substituted by still unknown M-theory. The popular dissemination of string theory to non-experts violates the most basic ethic guidelines.

– The arrogant attitude of many string theorists is also very well known. Please talk with some critics of them like Peter Woit or Glashow and learn the true sense of the word “pressure”.

– String theory is a mathematical goulash and a dishonest copy of formalisms developed by others. For example, after of decades of very wrong claims about the supposed TOE, now string theorist recognized that were wrong since usual quantization of string was not exact. Now they are launching the TFD version of string theory BUT TFD was previously developed outside of string theory. Again, non-string theorists were correct and “smart” string theorists (e.g. Witen Greene, Vafa, Schwartz, etc.) completely wrong. In fact, none string theorist did contributions to TFD. Even some string theorist has recently recognized that string theorists usually copy the work of others and after “rename” it like string theory.

– All past claims by string theorists were shown to be false, absolute all! In fact, the popular idea of that pointilike particles would be substituted by one-dimensional strings has been superseded by recent M(atrix) formulation by Banks and others, which is basically a quantum mechanics of pointlike particles (D0-branes). People again are ignorant of that, since that, like openly admitted by some theorists, the old name “string theory” is maintained by marketing purposes.

– It is also well knonw and denunciated in several occasions that string theorists have ignored other approaches to quantum gravity. It is very hard for a loop theorist to hear in a popular talk –given by a string theorist– that string theory is the only approach to quantum gravity. The only game into the city!

– It is also well known that young researches were forced to research into string theory because financial support of other theories was stopped in departments, funding agencies, and others due to aggressive string marketing activities. Many young physicists begin a PhD on string theory, discovered that string theory was a waste of time (real string theory is not the same that popularised version of string theory), and leaved the field. Some of them feel…

– Let me take a simple example from chemistry. According to “ignorant” and very arrogant people like Ed Witten, string theory is a promising TOE and reduces all of others sciences, e.g. chemistry. A moment, chemists know that is false, the reduction of chemistry to physics is a myth, as brilliantly explained in innumerable papers in Foundations of chemistry and others journals. Interestingly, 30 years ago some chemists were working in advanced formalisms for explaining behaviour that cannot be studied with usual methods. If you compare the very advanced theoretical work developed in the 60 and 70s with corresponding string theory status you found that string theory was wrong like a TOE even a joke. String theorists, arrogant as they are, ignored all of that and claimed that all of chemistry was an application of string theory. String theory was so advanced that no one other theory could provide to us an explanation of nature more profound, they said. Of course, chemists smiled, like they smile in the 20th century, when physicists (including Nobel laureates like Stark) attempt to convince to them that chemical bond was modelled by classical electrodynamics and that Lewis bond theory was, in simple words, nonsense. Now in the last part of 90, some string theorist discover that all past claims were wrong and are developing a new version of string theory called non-critical one. It is interesting that all past quantum methods and basic stuff is abandoned whereas work developed in the 60s by chemist Ilya Prigogine (see for example his Nobel lecture) used for a radical generalization of old string theory. But the ideas used NOW in string theory were developed in the 60s by other people! Prigogine and others were correct, string theorists again wrong. Interestingly, the ideas of the 60s have been updated in the 90s by the Prigogine and co-workers. Therefore, the current “radical” generalization of string theory by string theorists is, again, an outdated theory. This is real status of string theory; an authentic revolution if one read that masterful piece of marketing called the Elegant Universe (by Brian Greene) and focused to laymen, but claimed to be “very conservative” and outdated in the recent conference Quantum future by expertises that know stuff. Said I again once more? The first step for any serious theorists is to read previously published literature and then develop a better theory, but crackpots are specialist in ignoring the scientific method. If string theorists continue to develop a really outdated theory at one hand and arrogantly claim that are doing (they believe that in their infinite ignorance) the most important, the most powerful, the most fundamental theory at the other, then they would feel comfortable with the mocking of their colleagues. If Brian Greene, offensively claim in his talks that we may quantize everything, and Dyson convincingly reply him saying that Greene is providing no solid arguments in his belief, the problem is not with Dyson, the problem is with Brian Greene, that would first study serious stuff before doing irrelevant claims surrounded by a halo of pomposity.

– Etc.

Sincerely, I believe that non-string theories have been very generous with string theory community. String theorist would please to us our kindly attitude.

Once “refreshed” your memory, let me now comment some of your points.

The idea of that string theory is the most promising way to reconcile gravity and quantum mechanics, is one of well-established myths of literature. In an absolute sense, loop quantum gravity is so “successful” like the strings but in a relative sense (successes / total number of researchers), the loop approach has been around 10 times more satisfactory. Please, let me remember to you again that string theory has been substituted by M-theory.

It is false that “string theory” is based in one-dimensional loops. In fact, you appear to unknown the current joke on Internet that say that “string theory is now a theory without strings”. Yes, you obtain a remarkably rich structure, but just at mathematical level.

It is false that string theory predicts or explains gravity (this is another myth). “To predict” a massless spin-two particle is not the same that quantum gravity. In fact, causality is defined on a flat fixed metric with graviton modes arising in the perturbation, which violate GR basic idea of that full causality is defined in the full metric. This has been the main criticism of general relativists and loop theoreticians during decades. Now, string theorists are recognizing that great mistake (in the past they claimed that one would not take GR “too seriously”) and are unsatisfactorily searching for a background independent version of the old (outdated) string theory.

“In string theory, you just say the word “strings,” and gravity leaps out at you whether you like it or not.” This is not true, in fact one use previous ideas from GR, like to leave “freedom” to the metric into the string action. Somewhat like we need know previously that universe looks 4D and then introduce an arbitrary (that is by hand) compactification 10D -> 4D x 6D.

“At this point it’s a little unclear what the fundamental building blocks of string theory are” It is clear that string is NOT the fundamental entity into the non-perturbative regime.

“One often hears that string theory simply makes no predictions, but that’s clearly false. If you scatter two particles together, string theory unambiguously predicts that the cross-section should look stringy, not like that of fundamental point particles.”

Humm, even ignoring that prediction really mean, this is another myth. Let me simply quote to D. Friedan:

“Even if some particular macroscopic background spacetime is chosen arbitrarily, by hand or by ‘initial conditions,’ string theory still fails to be realistic at large distance. The large distance limit of string theory consists of the perturbative scattering amplitudes of the low energy string modes, which are particle-like. But the particle masses are exactly zero, and the low energy scattering amplitudes are exactly supersymmetric. String theory fails to provide any mechanism to generate the very small nonzero masses that are observed in nature, or to remove the exact spacetime supersymmetry, which is not observed in nature. More broadly, string theory is incapable of generating the variety of large characteristic spacetime distances seen in the real world. 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.”

The problem, of course, is not the popular statement of the difficulties for testing Planck-scale physics as you incorrectly argue; the problem is that nobody has obtained the successful standard model from string theory. A first step of any new theory is obtain that is already known before predict any new (including Planck-scale physics). So string theory is not compatible with available experimental data. “it’s just that we are as yet unable to test them.” As explained above, this is wrong.

“Recently there has arisen another sense in which string theory purportedly makes no predictions, associated with the ‘landscape’ of possible string vacuum states.”

“Well, too bad. It would have been great to make such predictions, but the inability to do so doesn’t render string theory non-scientific.”

No comment!

“… and possesses a mathematical beauty that is so compelling that the theory simply must be correct.”

The world is as it is, no that we like we want that it was. Mathematical beauty is a guide newer a justification. Moreover, string theory is rather ugly, at least for me. About his supposed “beauty”, sceptics suggest that string theorists try to colourfully camouflage the well-known theory’s flaws, like “a 50-year-old woman wearing way too much lipstick”.

“These kinds of arguments just don’t carry that much weight with the non-converted.”

Yes, I believe that “converted” is the correct word to use here. String community looks like a sect or, in the words of one of its most famous members, “a kind of a church”. It is not science.

“it’s the most promising way we know to quantize gravity. If there were multiple very successful ways to quantize gravity, it would be important to distinguish between them experimentally; but so long as the number of successful models is less than or equal to one, it makes perfect sense to make every effort to understand that model.”

This marvellous piece of promotion just emphasize the myth of string theory is the only game in the city. Please read literature in semi phenomenological approaches to quantum gravity and recent advances in other theories like LQG and predictions for the future LHC.

Yes, the comparison between Microsoft and Apple Linux is correct!! Microsoft is a layman-oriented business, whereas Apple or Linux are more specific but more serious. Moreover, it is well knonw that windows OS is a copy of graphical Apple OS and certain kernel properties of Linux/Unix. The success of Windows is in marketing and layman orientation, somewhat like string theory. It is interesting remark that when Microsoft presented the revolution of the trash icon, graphical copy and paste, multitasks, and others features in his first versions of windows, all of that was already known for decades for Mac users. Remember the famous Windows blue display. Yes, your comparison is really good!!

“It didn’t have to work out that the entropy of a black hole calculated from semiclassical gravity ala Hawking would be equal to the entropy of a corresponding gas of strings and branes, but it is.”

Another myth!! Loop quantum gravity obtains the entropy of Schwarzschild black holes. In “string” (really brane) theory, one traditionally has worked with BPS and idealized models of black holes. Strictly speaking, the “traditional” results in string theory do not concern, precisely, black holes, as they are found in a limit in which the gravitational constant is turned off. But they concern systems with the same quantum numbers as certain black holes. There is a kind of analogy instead of an identity with GR black holes.

Dear Peter,

“You seem very proud of knowing what is in the first chapter of Polchinski”

It’s chapter 6.4, Peter. Get a copy and try to catch up.

“The point I was making that you seem to have trouble following was just that if you don’t really know what your theory is, and all you have is a perturbation series which you hope is asymptotic”

What you say is true: the different perturbative formulations are probably only asymptotic series. On the other hand they are dual to one another. OK, that’s not a very concise definition, and it’s hard to do calculations in the “middle” of moduli space. In the realm of each perturbative formulation a wealth of information on non-perturbative aspects is available (worldsheet instantons etc. pp.). Sure, we are quite anxious to tie this all together and find the underlying fundamental symmetry principle. But until then we have a good non-perturbative definition that consists of these many parts and aspects. Claiming that, absent the final concise definition, nothing can be done is simply false.

I personally think that there is a lot to do. Along the way we’ll have to kill off the landscape and pay more attention to certain mathematical details that didn’t seem to matter too much up to now. It will be fun and worth every hour of work.

“you don’t know what the value of the coupling ”

Well, we haven’t found the way string theory selects the vacuum we live in. But we are able to consider various backgrounds, some of which are semi-realistic, and we know precisely what the coupling is in all of these cases. Furthermore, remember that there are stringy features common to any and all backgrounds. It’s still in Chapter 6.4 of Polchinski…

“you can’t reliably compute anything”

Look, Peter, You know it better. In QFT you have to choose a gauge group and fix a variety of parameters by hand before you can compute things. In string theory, at the present level of our understanding, the equivalent procedure is to choose a point or region in moduli space and a background. Once you do that, you can reliably calculate almost anything you want, at least in principle. The great advantage of string theory is that it naturally includes quantum gravity and that there likely is a dynamical mechanism that should eventually tell us what the background and moduli are (at the present age of the universe ðŸ˜‰ ). QFT has no hope of doing either. That’s why we take the stringy extension of it so seriously.

“He’s a real poster boy for string theory.”

Thanks for the flowers. I wasn’t even so kind to you as to deserve this kind of compliment.

“let’s first hear your qualifications”

No, thanks, I don’t need this silly kind of publicity that you use as a substitute for an academic career.

“Are you the socially retarded teenager you appear to be? Maybe an undergrad?”

No, but I wish I was that young. My social abilities have no bearing on the present discussion, do they? I have already conceded that it is reasonable on your part to consider me an a*hole and, if you want, a nerd.

“My qualifications include a 1985 Ph.D. in particle theory from Princeton, postdocs in physics at Stony Brook and math at Berkeley (MSRI), four years as an assistant professor at Columbia, and currently I’m a non-tenured full-time faculty member at Columbia with the title of Lecturer. I regularly teach graduate courses here, including one in quantum field theory recently.”

Congratulations, that’s a bunch of nice accomplishments. So why do you act like a chief bully now instead of being proud of yourself?

Torbjörn,

I don’t think that neither you nor Michael grasped the discussion over at Lubos’ blog. For five years, I and Lubos have disagreed about the consistency of gauge anomalies. His argument was always “A gauge symmetry is a redundancy of the description, you idiot”. With my last post, I think I convinced him that he was wrong, since a counterexample can be found in the most elementary chapter of GSW. Boy, that must have hurt ðŸ™‚

In other words, Peter is a professor who has accountability instead of tenure. I like it.

-drl

I’ve been traveling, so internet access is intermittent. I’ll probably soon try and delete some of the more off-topic posts. I’ll leave the ones from Michael, whoever he is. He’s a real poster boy for string theory.

Michael:

You seem very proud of knowing what is in the first chapter of Polchinski, but do you know anything else about physics. The point I was making that you seem to have trouble following was just that if you don’t really know what your theory is, and all you have is a perturbation series which you hope is asymptotic to the real, unknown thing, and you don’t know what the value of the coupling is, you can’t reliably compute anything, and so you shouldn’t be claiming to have predictions. Did you follow that? Do you have a counterargument?

Before we hear your counterargument, let’s first hear your qualifications. Are you the socially retarded teenager you appear to be? Maybe an undergrad? My qualifications include a 1985 Ph.D. in particle theory from Princeton, postdocs in physics at Stony Brook and math at Berkeley (MSRI), four years as an assistant professor at Columbia, and currently I’m a non-tenured full-time faculty member at Columbia with the title of Lecturer. I regularly teach graduate courses here, including one in quantum field theory recently. OK, what about you?

Michael,

If you are such a hotshot string theorist, why aren’t you over there discussing it with the other big boys and girls?

Hi Torbjorn,

I think it’s great if “laymen” take interest in physics and string theory. I personally welcome everybody to talk and discuss such things no matter what their level of education or background might be.

What I dislike is pretenders. Why would Peter Woit, who’s academic career ended in 1989, be in a position to lecture people like Sean Carroll and even Jacques Distler on string theory? This is disingenuous. If he were to ask or to try and understand, that would be great. Instead he is putting out bold claims debating professional physicists. In the process he reveals gaping holes in his knowledge of the subject’s very basics. For example, the soft behavior of string scattering amplitudes is covered in any 1st semester grad course on string theory and is explained in detail in Polchinski’s 1st volume. Yet Peter Woit essentially bases one of his arguments on the assumption that such behavior does not exist. His comments on perturbative vs non-perturbative physics are seriously confused, too. This is something he ought to know, having received a PhD in theoretical physics in the 80s. You know, there is a huge disparity between what he knows and is capable of, and what he pretends to be.

Please do not think that I do not welcome reasonable thoughts and arguments by everyone — even Peter Woit.

Maybe Michael is the same as who attacked Thomas Larsson over at Lubos blog.

That Michael was probably correct; this one is seriously wrong.

Obviously there are non-knowledgeable people who can find interest in the discussion; I am one of them.

We will discuss ST whether or not practicioners take part. If they don’t the discussions will be poorly informed.

And to try to supress the discussion is Not Even Wrong; it will lead to resentment and bad-will.

Nigel:

It was not false when they said that ST is the currently accepted theory, and it was not personal. It would be best if you can accept that.

Science is not democratic. It needs a democratic society, but nothing in the process of science itself is using democracy.

The Higgs boson explains inertial mass, which by Einstein’s equivalence principle is the same as gravitational mass.

“Super string theory is even worse than astrology because it does not make any prediction at all. It hasn’t even made even an astrology type of ambiguous and bad predictions. ”

Quantoken, you have hit the nail on the head. The ‘soft stringy’ theorists are charlatans, always hoping to one day make a ‘prediction’. Other people have to produce results to earn a living.

Michael said:

“How can I insult what does not exist? You are not a string theorist, wake up. Your pathetic obvious mistakes over at cosmicvariance.com are evidence enough. You don’t know about the uniquely stringy “soft” behavior of string scattering amplitudes. And you are unable to see that non-perturbative aspects don’t matter in the IR. Among many other things, this shows how little you know.”

It does NOT matter a bit at all whether Peter has intimate knowledge about super string theory or not. It works the same way that Peter can confidently criticize astrology

withoutnecessarily knowing any thing about astrology at all. Any one with the least bit grasp of what astrology is can safely criticize astrology as superstition, because it does NOT make good predictions. Super string theory is even worse than astrology because it does not make any prediction at all. It hasn’t even made even an astrology type of ambiguous and bad predictions.So, knowing just that little bit of knowledge of the fact that super string theory has not made a single prediction, is sufficient enough to allow any one to criticize super string theory. I believe Peter knows at least that much of the facts, so he is fully qualified to be a criticizer of SST.

My point is one can waste decades of time to pick up tons of intimate math skills needed to “research” super string theory, but it still does not add you a single ounce of knowledge about the nature, since so far super string theory has proven no relevance to the nature and does not go beyond a mere mind exercise so far.

An obvious thing that I want to point out is no one is smart enough to change natural laws.

If the nature is inheritantly not a 10-D world, there is no way you can correctly describe nature using a 10-D theory, no matter how smart or how hard you try. It’s a dead end.Quantoken

‘String theory’ doesn’t exist, what does exist is speculation. Serious people have better things to do than mudslinging over trivia of no consequence, that predicts nothing, leads nowhere, and cannot be tested. By Popper’s definition of science as being merely tested speculations, ‘string theory’ is not science. What part of this can’t the ‘string theorists’ grasp?

“Are you honest and realistic enough to know that you’re a gutless asshole?”

Yes, I guess I’d feel that way if I were you. And I understand that my blunt ways must be painful for you. Judging by the vulgar expressions you use: very painful, indeed.

“I wonder why you’re insulting my competence”

How can I insult what does not exist? You are not a string theorist, wake up. Your pathetic obvious mistakes over at cosmicvariance.com are evidence enough. You don’t know about the uniquely stringy “soft” behavior of string scattering amplitudes. And you are unable to see that non-perturbative aspects don’t matter in the IR. Among many other things, this shows how little you know.

Wonderful discussion over there!

Hi Michael,

Are you honest and realistic enough to know that you’re a gutless asshole?

Either you’re the 12 year old you appear to be, in which case I wonder why you’re insulting my competence, or you’re an adult string theorist, in which case you may (or may not) know more about string theory than me, but are definitely a really sad case.

Posting this kind of shit from the protection of anonymity is pathetic. Grow up, whatever age you are.

Why do you think the discussion might be interesting? You are not exactly knowledgeable in the area. I hope you are honestly and realistic enough to know that.

I guess it’s postmodern cool to offer a defense of abject idiocy.

[ physics, strings ] = ih

-drl

“Two Cheers for String Theory” wasn’t exactly a ringing endorsement. It was lukewarm at best.

One of the quotes was: “If true, this puts a damper on the hope that string theory would predict a unique vacuum state, and we could explain (for example) the ratio of the muon mass to the electron mass from first principles.”

It turns out that if you square the sum of the square roots of the masses of the electron, muon and tau, you will end up with a mass that is exactly (to exp. error) 1.5x the sum of the masses of those three leptons.

I suggested this as evidence that the standard model was incomplete to an older physicist. His attitude was, “so what?” From his point of view the masses were arbitrary and it really didn’t matter if they happened to fall in some sort of pattern.

Funny that he didn’t feel the same way about the coincidences that the standard model managed to explain.

Carl