The editors at Seed magazine have started a new blog about science called sciencegate, which contains a wide variety of interesting material. One of the recent postings is called Strung Out on the Couch; it’s by Joshua Roebke and not exactly complimentary about string theory. Here’s his analogy for the current situation of string theory:
Think of it this way, a precocious little genius, who everyone has been touting would do great things in the world, finally grows up. Now imagine he’s 30 years old, living at home having not accomplished much, and his mom keeps going on about how great he is and is still going to be. You’d probably just want to tell him to grow up and make something of all that potential instead of just talking about how he’s going to get off the couch.
Before Lubos and others start the usual personal attack on any string theory critic as not knowing anything about the subject, it’s worth pointing out that Roebke spent several years as a graduate student working on string cosmology before leaving academia.
Sciencegate – sounds like a big scandal these days…
Boy, who is this Joshua Roebke? Please present list of his publications, otherwise its difficult to judge from his repetitive and, I may add, boring piece whether he came to these conclusions himself after working hard many years in ” string cosmology”, or he is just this blog’s big fan and read a couple of articles in new york times and such. As far as I checked arxiv.org produced no records of Joshua Roebke.
I am in no way trying to “personally attack” you, but , in my opinion, unless you Joshua Roebke have actually wokred in the area on the level to produce something more or less deserving attention of the community, your comments have zero value. Who are you to comment on string theory?
What is it with you people? Why everyone thinks starting his own blog is a good idea? Everyone is confident that his thoughts are the correct ones, “everyone else is stupid, I am smart”
Dont start a blog, there are more than enough blogs, Peter doing his job quite well already. Just go home , or better go to your office, sit there from 8am to 8pm, and work on a problem. Maybe you will feel better.
Apparently stringists can produce any number of possible universes from their theories, except it seems, the one we live in.
I think it is time to formulate this as a scientific hypothesis “the anti-string hypothesis”:
Our universe is uniquely determined, by the inability of string theory to approximate it.
“who is this Joshua Roebke?”
Well, first of all “A.”, who are you? Don’t you think it’s kind of disgraceful behavior to attack others from behind the cloak of anonymity?
It’s funny how predictable string theory partisans are these days. When Roebke wrote to tell me about the Seed blog and what he’d written for it, I wrote back to tell him I’d be happy to mention it here, but I could confidently predict his professional competence would be immediately attacked by Lubos and various others of his ilk. If you actually had any arguments to answer the ones Roebke is making, you’d be making those and not instead attacking his fitness to make those arguments. But go right ahead and behave like this, by doing so you and others are doing a great job of convincing ever increasing numbers of people that you are both intellectually and morally bankrupt.
If he’s in the mood I suppose Roebke can defend himself. I have met him and can tell you that his understanding of string theory appears to be consistent with what you would expect given his background, that of a good physics Ph.D. student who did research for a while in the subject, but ultimately decided to do something else. Your criterion that no one can criticize string theory unless they have written papers on the subject is that of a member of a cult convinced that only the opinions of true believers are of any value. By now lots of smart people have gone through the experience of spending years of their lives learning about string theory, finally reaching the point of realizing that the theory hasn’t lived up to its promise, and that devoting the rest of one’s life to working on it might not be such a great idea.
A reason to post here anonymously: M O T L never forgives
A reason to post here anonymously: M O T L never forgives
This is nonsense. Lubos and I have had loud public disagreements in the past; check out the sci.physics.research archives. I don’t believe he bears me any ill will.
Ralph said:
“Our universe is uniquely determined by the inability of string theory to approximate it.”
Classic! I loved this quip so much I had to applaud it with this comment. Thanks Ralph. It’s as if the blind men are feeling everywhere the elephant isn’t.
Loop Quantum Gravity is teh suck!!1! It is for the losers and the nerds.
Kool kids do teh strings. They might have lots of vacua but they also have lots of funding money and womens LOLOL. Also they use kool words liek heteroteric so they are the real daddy. And they have simetries in hodgy-podgy mirrors too!!
Dear A.:
You say:
What is it with you people? Why everyone thinks starting his own blog is a good idea? Everyone is confident that his thoughts are the correct ones, “everyone else is stupid, I am smart”
Dont start a blog, there are more than enough blogs, Peter doing his job quite well already. Just go home , or better go to your office, sit there from 8am to 8pm, and work on a problem. Maybe you will feel better.
Internet is just like that: you will find a broad spectrum of material, from garbage to excellent. The same is valid for blogs of course. I have started my own blog even though I know several of them, from garbage to excellent. At the same time, I never thought that “everyone else is stupid, I am smart”. Maybe a lot of people think like that, but I am sure many do not.
I am not here to defend one approach to quantum gravity or another (much less the people involved), nor to say that I have a good blog. I am interested in all of the ideas towards a quantum theory of gravity as long as they seem sufficiently sound or look interesting enough to me. That is my blog. Yet, I do work from 8am to 8pm, or even more, and that involves several responsabilities as well as my own personal projects. So having a blog is not incompatible with doing hard work. This is valid for many people, as much as it is not valid for many others.
There is a little more I would like to comment on blogs. We are living in an epoch were ideas on quantum gravity are being constructed. It is a formidable problem. I see this as a very exciting period in the history of physics, and the various discussions I read daily in the (good) blogs are, to my opinion, very illustrative of our times. So these blogs are useful, and in some sense will serve as unique testimonies of our struggle towards quantum gravity.
Now, concerning the problem of who should be considered competent to “judge” a given approach. It seems clear to me that “judgement” is a strong word and an inappropriate one in science, except from the point of view that nature is always the final judge, since it is obviously nature what we want to probe, describe and ultimately explain.
Intelligent and constructive criticism is what is necessary in order to make progress. But this is hard to find. String theory in particular does not “help”, and it is a good example in that sense. It requires years and years of very hard work in order to gain some knowledge of its basics. So, it seems inevitable you must be an expert to say something technically valuable considering the huge amount of mathematical material involved.
At the same time it is an obviously tricky or paradoxical situation, specially when one finds out that apparently there are no predictions of the “theory”. So, considering this state of affairs, it seems natural that one needs not to be an expert to have the strong impression that it might be “not even wrong”.
I must say I share this overall impression, although I am not saying I have a final position on this. I am not competent enough to offer a reasonable or more technical criticism on this matter, so I stop here to go for my daily hard work.
A final, perhaps also obvious thing: technique or knowledge is nothing without wisdom, but that is another story.
I am in no way trying to “personally attack” you, but , in my opinion, unless you Joshua Roebke have actually wokred in the area on the level to produce something more or less deserving attention of the community, your comments have zero value. Who are you to comment on string theory?
Is this a parody? I hope so….
The difference between string theory and ID, BTW, is that string theorists dream of making positive statements. IDers never will.
I think the problems with String Theory go way back to the beginnings of Quantum Mechanics or Quantum Field Theory. There was a misconception as to what was needed to bring them together with General Relativity.
The fundamental difference between QM and GR is that, in the former, observables are operators (or at least are the results of operators acting on states to yield eigenstates). In GR they are pretty much just functions—functions of many variables, but still just functions, just as in classical physics. Getting a unification means, at the very least, having a mathematical formalism that represents the observables in one single way. But then, going backwards, it would be possible to recast QM in that same formalism, but just neglecting gravity. We would then have the revised mathematical structure for QM with the measurement problem—just what so many now want.
But I think this got fudged way back at the beginning. The Copenhagen interpretation effectively hid the interesting features of QM, and masked the important mathematical structures: the state space K of pure and non-pure states, the self-adjoint operators and their awkward formal properties. (Just how much of what is true of bounded operators really carries over to the unbounded case?)
These things got buried. And quantum field theory seemed to adopt a purely heuristic attitude to QM. It took the little bits that it liked—Heisenberg Uncertainty, transition probabilities, the Planck length—and downplayed the rest. You could read what particle physisit’s wrote and think for all the world the universe was still basically Newtonian. And as time has gone on this cavalier attitude to QM seems only to have gotten worse.
String Theory is just the culmination of a long period of not getting the fundamental problem and sweeping the real difficulties under the rug. The renormalisation problem was the real clue that something had gone very wrong at a basic level. The calculational sucess of QED just allowed the sleepers to stay asleep.
Now we have a very elaborate mathematical structure that has no contact with reality. But given the history this was bound to happen. Physists started out fudging the conceptual issues and caring only about the calculations—the irony is that we have no more calculations to care about, but we have a whole lot of bad concepts.
Just my 2 cents.
Sorry, that should have said:
”We would then have the revised mathematical structure for QM without the measurement problem—just what so many now want.”
Anonymous Says:
Is this kind of crackpotism, which does make tested and testable predictions by the way, would be easy to write off as crazy.
I think there is a perceptible difference between “crackpotism” and “theory under construction”. Baez index list on the former is a good reference to unmask potential crackpots; scientific method on the latter is usually enough, and the result is progress or refutation.
A “grey zone” however is always possible and that is where the danger lies. This is specially symptomatic when theorizing about nature at regimes where experimentation is very difficult or observation relatively inaccessible. So you have a “theory under construction” that cannot be adequately or promptly investigated under the conventional rules of the scientific method. One may even end up with a mathematically consistent formulation, but in what sense it is satisfying? One may think it is “beautiful”. One may think is the only proposal for a given problem. So this is the grey zone because it is all under the umbrella of personal taste.
I had the curious experience a few years ago of giving a talk on the basics of braneworld scenarios to a mixed audience of astrophysicists ranging from specialists on gravitational waves, CMBR, high energy, extragalactic, galactic and stellar astrophysics. This is a much harder audience than a general public audience, because these people are well versed in the scientific method. They deal with very, very hard problems, and even problems that may need new physics. Although I did my best and they enjoyed the talk, most of them thought there was something quite disturbing on the overall idea. I am sure this is symptomatic of the grey zone.
As I see it, the only obvious way out is to work as hard as possible on the problem of identifying possible observable effects of a given quantum gravity proposal as it is being constructed and look for these effects, otherwise one is hopelessly stuck in the grey zone, sometimes without even being aware of it.
In reply to Michael at 7:14 PM, just what constitutes a research program in ID? There would be scientists receptive to ID if there existed any sch thing. ID is intellectually sterile. String theory is far from sterile, its problem is that its productions don’t yet make contact with the real world.
Peter, I think you did Joshua Roebke a disservice by not including the lines just previous to what you quoted.
Joshua Roebke said:
“I actually love string theory and think it’s light years ahead of other theories.”
Oh sure, how could you not be light years ahead of others, if you started several decades before other theories were first proposed, and you have several orders of magnitude more researchers working on the fields, and many times more public funding invested in supporting you. Surely you are light years ahead of other approaches.
But it doesn’t make you look good. What matters is are you on the right direction? You are on the wrong approach. So the further light years you go forward in your dead end, the further away you are from the ultimate answer!!! Look at the 10^500 landscapes figure. You may be light years ahead but you have another 10^500 light years to cross in your front. Mean while the theory that is on the correct approach doesn’t need to go a light year: It only needs to reach the moon.
I think there is a perceptible difference between “crackpotism” and “theory under construction”.
Unfortunately cargo-kult-science according to Feynman does anything right, is a true slave of scientific ritual and jargon but is nevertheless not science. This reminds me somehow to the old catholic problem off finding a true saint or a real representative of god obtaining all the priviliges of god including the permission to kill. Both science and religion are hunted by their own double or shadow.
It is interesting that you find the difference “perceptible”. Ususally strong differences do not follow from something as subjective as perception in particular the perception of strange social behaviour but from a certain axiomatic or precise and objective diagnosis. Misusing authority is therefore not so much an accident in evaluating competing researchers work but has to be expected. On the other hand the theory of social systems provides a self-referential answer presupposing a running science business: viable is what gives rise to connectivity. As an addition of my own I would guess that connectivity is not only a conservative mechanism of affiliation in modern societies but can be understood more dynamically like trading commodities on a stock-market.
A said,
If this argument is correct then string theorists can only talk about string theory since they have seriously studied nothing of real word. Please using your ‘argument’ explain to Schwartz he cannot talk about BH-paradox because has provided none work on the topic, please explain to Witten that he cannot talk of chemistry since has published not a single paper on the topic, please explain to Brian Greene that he cannot write on measurement problem of QM since has published a single paper, please explain to Lubos that cannot write reviews of books on environment science since he never published a paper on the field,
etc,
etc,
etc,
etc.
Juan R.
Center for CANONICAL |SCIENCE)
If it is of interest, i have posted directly some basic comments on the Joshua Roebke post highlighted by Peter Woit
I basically agree that string theory is a disaster.
Juan R.
Center for CANONICAL |SCIENCE)
Please stop with the attempts to turn this into a forum for discussion of religion, intelligent design, the anthropic principle, your favorite ideas about physics, etc., etc., none of which have anything to do with the topic of the posting. I’ve just deleted about half of the comments on this thread and will keep doing so if I feel it is necessary to keep this comment section from turning into something completely depressing and unreadable.
ks Says:
It is interesting that you find the difference “perceptible”. Ususally strong differences do not follow from something as subjective as perception in particular the perception of strange social behaviour but from a certain axiomatic or precise and objective diagnosis.
Perhaps “perceptible” was not the right word for what I meant to say. In any case, if I understand you correctly, I agree that it is unfortunate that researchers are not usually evaluated according to a well defined, precise criteria, but mostly from his/her “social resources” (“colleagueship”) — or lack of them. Be a colleague of an “authority” and you have good career chances, whatever the value of your research. I have been through this before. Sorry if I misunderstood you on this matter. Also, I should be more careful with the words I use. In any case, perhaps this is becoming off-topic, and I fear Dr. Woit will not like it.
‘Think of it this way, a precocious little genius, who everyone has been touting would do great things in the world, finally grows up. Now imagine he’s 30 years old, living at home having not accomplished much, and his mom keeps going on about how great he is and is still going to be. You’d probably just want to tell him to grow up and make something of all that potential instead of just talking about how he’s going to get off the couch.’
Peter, explain how someone can make a cheerful comment 😉
I think Joshua’s article takes approximately the right tone towards string theory. It is not yet certain that srting theory will never be able to make a prediction, although there are some signs that this might be the case. The real problems for physics are the position that string theory has taken in the common view of theoretical physics as the only option available and the fact that young theorists don’t really have any career options apart from string theory or condensed matter, while faculty positions are increasingly being occupied by string theorists at the expense of other legitimate research programs.
There is, of course, a separate problem with the string theorists themselves, namely that they are arrogant and narcissistic, to the degree that they dismiss all non-string theorists as idiots and all non-string theory physics as irrelevant. String theory shows practically all the signs of groupthink, namely:
1. Illusion of invulnerability
2. Unquestioned belief in the inherent morality of the group
3. Collective rationalization of group’s decisions
4. Shared stereotypes of outgroup, particularly opponents
5. Self-censorship; members withhold criticisms
6. Illusion of unanimity (see false consensus effect)
7. Direct pressure on dissenters to conform
8. Self-appointed “mindguards” protect the group from negative information
Lubos would no doubt be pleased to know that he is a “mindguard”.
On the subject of intelligent design, it might be instructive to see how A’s comment looks from that point of view:
I am in no way trying to “personally attack” you, but , in my opinion, unless you have actually wokred [sic] in the area on the level to produce something more or less deserving attention of the community, your comments have zero value. Who are you to comment on intelligent design?
Hi,
What is ID that some of you mentioned?
Thanks
Pseudo
ID=Intelligent Design, but please, don’t take this as an excuse to start discussing the topic here.
Intelligence Deficit, which by definition is
ID = (100 – IQ)/IQ
A negative ID is a sure sign that IQ
String theory predicts the BH entropy formula, string theory predicts a 10-dimensional space-time, string theory predicts how particles interact at [tex]10^19[/tex] GeV. STRING THEORY MAKES PREDICTIONS. The difficult task is going from [tex]10^19[/tex] GeV to the actual energy that can be reached in experiments.
In any case, if string theory is a wrong physical theory, string theory has given a great amount of mathematical results, and it is a respectable endeavour of the human mind.
Jose,
1. It would take too long to go into the exact status of black hole entropy calculations in string theory, but there is no solid “prediction” for physical black holes, at best an argument that you get the semi-classical limit that you expect for any thing that deserves to be called a quantum version of gravity.
2. String theory doesn’t predict 10d spacetime (have you heard of M-theory?). And if it did, there’s the problem that we only see four dimensions.
3. String theory doesn’t predict how particles interact at the Planck scale (have you heard about M-theory?).
STRING THEORY MAKES NO PREDICTIONS. NONE WHATSOEVER, NADA, ZIP.
Jose Said,
String theory does not predict BH formula because i) compactification is done by hand, ii) string theory ‘BH’ are highly idealized objects are not general relativity BH, iii) etc.
String theory does not predict a 10D spacetime. The 10D spacetime is introduced by hand, with a strange ‘compactification’ of the rest 16D. Not forget that supersimmetry is not correct at low energies. Not forget that all 10D are equivalent and for comparison with observed 4D universe, 6D may be differentiated by hand. Not forget that a new dimension is hidden in the perturbative regime. Not forget that still nobody know if 11D is the correct dimensionality for M-theory, etc.
The ‘prediction’ (of course there is not prediction because topology and geometry of background spacetime and others features are choosed by hand) of interactions at 10^19 GeV are just scattering amplitudes with the wrong large distance limit. There is not dynamics, there is not adequate classical limits (GR causality structure is broken when taken classical limit of gravitons), etc.
Etc,
Etc,
Many other theories give mathematical results. Moreover, the real impact of string theory on math is easily sumarized:
epsilon, when epsilon –> 0.
I, at least, am able to distinguish between math and physics. For example between NC geometry (math) and M(atrix) theory (physics).
Juan R.
Center for CANONICAL |SCIENCE)
Woit, religion makes more predictions than string theory!
Religion predicts a day of judgement! Religion predicts sinners will go to hell. This is perfectly testable: die and you’ll see… Religion predicts all kinds of things that you can test if you are desperate enough…
String theory merely predicts 10^500 universes, a landscape of universes, that there could be any number of branes, and so forth.
I think you’ve got to start saying that string theory is not ‘as bad as religion’, but rather that religion is a lot more scientific than strings. Be honest!
Peter,
> STRING THEORY MAKES NO PREDICTIONS.
a standard argument (I guess E. Witten is the author) is that string theory predicts supersymmetry [*]. Of course, we do not know at which energy scale we may see it…
My question to you is this:
Assume that the LHC (or ILC) will provide strong empirical evidence, e.g. for a MSSM or NMSSM model.
What would be your reaction?
[*] Lubos became quite angry when I stated once that string theory ‘assumes’ supersymmetry in order to be consistent; It is the same IMHO, string theory/M-theory requires supersymmetry at some energy level to be consistent, at least at our current understanding.
Wolfgang,
Where you say ‘string theory predicts supersymmetry’ you are really saying that Witten and others developed string theory so that it would do this. It is an ad hoc ‘prediction’, like epicycles.
Lubos gets angry all the time, you should know. Being a string theorist, he has a good excuse, because the news keeps getting worse.
If and when empirical evidence is found for strings, that will be the time for it to be taken seriously. The whole problem is that it is being taken seriously by the world now, when there is no evidence.
Wolfgang,
It doesn’t really make sense to “predict supersymmetry” if you then say it may be broken at arbitrarily high scale and be indistinguishable from no supersymmetry. The real question is whether it is broken at LHC energies and can thus do one of the main things it is supposed to, solve the hierarchy problem. My guess is that the LHC won’t see supersymmetry and I’ll be surprised if it does, especially if it sees some random MSSM spectrum. If this does happen, that’s certainly some encouragement for the ideas that have led people to work on string theory, although far from solid evidence for string theory.
anon,
I am not very interesting in the syntax or semantics of the word ‘predict’.
Also I do not care if Lubos is angry (but he is sometimes entertaining when he is).
But I would like to hear Peter’s opinion, since he is a strong critic of string theory (like many here), but seems to really know QFT and particle physics. And my question is simple and straightforward:
How would you react if the LHC (or ILC) provides strong evidence for supersymmetry?
I would see this as strong evidence that superstring/M- theory is at least on the right track.
Peter,
ooops, seems that posts have crossed here.
Thank you for the response.
When you say
> If this does happen, that’s certainly some encouragement for the ideas that have led people to work on string theory
I interpret this as you saying “with strong evidence for supersymmetry I would eventually change my opinion on superstring theory” ?
Wolfgang,
Our comments crossed. I’d agree that supersymmetry at the LHC would be some sort of evidence that superstring/M-theory might be on the right track, although I wouldn’t go so far as to call it “strong evidence”.
It would also depend a lot on exactly what was seen and what sort of hints this gave about the mechanism for supersymmetry breaking.
That’s unfortunate. I think the semantics of this word is badly in need of review under the current circumstances.
It used to mean something very much like this:
An experimentalist finds a way to reproduce a particular effect, which they characterize with one or more measurements. That is, they identify those features of the experimental situation that must be controlled to bring about the same effect (within certain error margins) in multiple runs of the experiment.
The experimentalist then says to a theoretician: “I can reproduce this effect, but I can’t explain it. Can you tell me why the effect occurs in this situation, ie, given the features I have identified, and also calculate the results I have measured using the features of the experimental setup as inputs to the calculation?”
Now, I would assert that the theoretician’s job is to do this, and do it with a minimum of auxiliary assumptions, ie, in addition to the theory (the explanation) being tested. Any auxiliary assumptions that are made should be independently verifiable by the experimentalist, so they cannot be freely used to fit the prediction to the result.
It appears to me that string theory in its current form must make extensive use of auxiliary assumptions that can’t be independently tested in order to make anything like a definite prediction of any given physical effect. Of course one could say, “well, I’m sorry if you don’t like it that world is this complicated, but this appears to follow from the basic principles of the theory. The world can be as complicated as it likes; we can’t dictate the structure of physical reality for our methodological and epistemological convenience.”
I would assert that in fact we must “dictate the structure of physical reality for our methodological and epistemological convenience”. In doing so we may find that those dictates are repeatedly violated, but nonetheless our theories must be as restrictive and unambiguous in their predictions as we can make them. If one thinks the world can be arbitrarily complicated then one might as well abandon any attempt at testable explanation, and simply accept the prima facie complexity of the observed world, along with whatever interpretive mythology one finds most comfortable.
It is not noted often enough that the deep symmetries of the physical world, and moreover, the decomposability of physical systems into largely independent parts, have great epistemologic as well as aethestic significance.* In a world like that of the astrologer, in which physical influences of arbitrary form and magnitude can be propagated over arbitrary distances at arbitrary speeds, one can hardly imagine any effective dialogue between experimentalists and theoreticians, or even among observers trying to reach intersubjective agreement about what they perceive. We have not been merely discovering what the physical world is like for the last several centuries; we have also been gradually discovering how it is possible for us to know the world at all. The anthropic principle offers an answer to this question that is perhaps suggestive but ultimately scientifically vacuous. There is yet reason to believe we can do better.
According to Amelino-Camelia et al. (gr-qc/0501053), “string theory may predict many new low-energy effects, but it can also be easily tuned to avoid all of them.”
I have just highlighted their paper today in my blog page (see their very nice fig.5).
That is a somewhat unusual usage of the word “predict”.
“string theory may predict many new low-energy effects, but it can also be easily tuned to avoid all of them”
What beautiful flexibility! Those who love string theory will be enchanted. Lubos will be delighted. Why bother testing string theory when it is so vague any result is consistent with it?
Amelino-Camelia et al. also write (page 11 of that same paper):
“The low-energy physics of String theory, as presently understood, could be very rich, with the presence of new fields and the possibility of a variety of new effects. This may provide the basis for a large phenomenological effort, even though one should keep in mind that the new effects are not genuine ‘predictions’ of String theory: String theory could make room for these effects but it could equally well suppress them all. It appears at present not possible to falsify String theory on the basis of low-energy phenomenology , but it would nonetheless be very exciting if any of the new effects that String theory may host was actually found.”
So it is clear enough that the motivation that Amelino-Camelia et al. focuses on is the search for new low-energy physical effects per se. They clearly state that string theory does not actually predict them, nor can be falsified by them, it just can accommodate them if one wishes.
I really look forward to a technical, non-passionate (if possible) opinion of string theorists and non-string theorists on this matter (specially on Amelino-Camelia et al.´s paper). If considered off-topic, please apologize and feel free to redirect to my blog page.
Wolfgang Said
Since string theorists like to claim that string theory does predictions, a brief historical review of ‘predictions’ would be interesting…
String theory began from his first failure on explaining strong force on a 4D world (and substituted by QCD), then predicted wrong Lorentz symmetry when extended and for correcting this wrong prediction 22 additional dimensions were introduced by hand.
Then, wrong dimensionality was predicted and for correcting this wrong prediction KK was introduced by hand.
Then, tachionic modes were obtained and this violated again experimental data, and for correcting this novel wrong prediction supersimmetry was introduced by hand.
Of course, string theory continued doing wrong predictions and evolutioned until the modern M-theory nobody know that is!
However, supersimmetry is a fascinating example of how string theory is wrong.
String-superstring theory predicts either
superimmetric non-tachionic world
or
non-superimmetric tachionic world.
Curiously our observed universe (at least at low energies) is
both non-superimmetric and non-tachionic.
Therein the extended criticism in relevant literature that string theory predicts nothing of this world.
If one follows scientific method (string theorists do not) then one may develop a first theory for:
– 4D Standard gravity and
– Compatible with non-superimmetric and non-tachionic known Standard Model.
At future HLC-data is supersimmetry found?
No problem, to generalize above theory adding supersimmetry to HIGH energies (NOT at all energies).
At future ‘cosmic-acellerator’ are hidden dimensions found?
No problem, to generalize above theory adding more dimensions to HIGH energies (NOT at all energies).
The 40 years failure of string theory is because string theorists want say how universe may be.
Science is about we can observe, NOT about we want observe and complete ignorance we really observe.
Juan R.
Center for CANONICAL |SCIENCE)
Juan, we have actually found supersymmetry 🙂 Perhaps Lubos is right after all.
Alejandro Rivero,
Since i said is crystal clear, it appears that after all Lubos is again wrong 🙂
If anyone want help to Lubos in his research, then may try to find a well-defined mathematical limit where superstring actions turn, at least, non-supersimmetric, all looks 4D at large distances, and masses are non zero.
Juan R.
Center for CANONICAL |SCIENCE)
is m-theory, are strings supposed to make up quarks (and electrons) directly, or do they make up preons which then make up quarks?
lubos has claimed m/string theory predicts BH entropy, but LQG does not. apparently john baez claims LQG does predict BH entropy. what is the status of BH entropy in LQG (and BI-like CDT) gravity?
dan,
see Lee Smolin said. Question 4 of page 60 of arXiv:hep-th/0303185 v2 11 Apr 2003.
BH entropy is ‘solved’ on LQG, whereas only partial results and many open questions remain on the string side.
I do not follow this topic in detail now (i discovered that string theory is a waste of time) , but some few years ago, string theorists were working with certain idealized states that they ‘believe’ that could explain GR black holes.
Yes! almost all in string theory are beliefs and conjetures…
See also section 6.3
Since LQG arises directly from quantization of GR field equations, the BH studied are more close to GR (Schwarzschild) BH.
Juan R.
Center for CANONICAL |SCIENCE)
I would like to draw everyone’s attention to the prefix “pre” in the word “predict”. It means “before”. In other words, it describes a situation where you guess it is going to happen before it actually happens. Examples of this are:
1. Maxwell guessed that it would be possible to observe a displacement current before anyone actually did. It was therefore a “prediction”.
2. On the basis of observed patterns of quantum numbers for baryons, Gell Mann “predicted” a baryon of strangeness -3 and mass of about 1680 MeV. In 1964, a particle fitting this description was observed. A fine prediction.
One can, of course, predict things which turn out to be wrong. But there are also things which never were predictions in the first place. For example:
1. Special relativity does not “predict” four dimensions. Four dimensions are assumed at the outset.
2. Superstring theory does not “predict” gravity. General relativity – a tested theory of gravity – is one of the inputs (although it is not clear that one can get it back).
3. Superstring theory does not “predict” supersymmetry. Supersymmetry is assumed at the outset.
I am happy to answer any further questions that anyone might have about the usage of this word.
“Superstring theory does not “predict” gravity. General relativity – a tested theory of gravity – is one of the inputs (although it is not clear that one can get it back).”
This is not true Chris if we suppose that particles are strings then we are led to the existence of massless spin 2 particles, that is gravitons, without more assumptions.
Jose is more or less right, but one could also say that there is a selection bias; mathematical formalisms in which Einstein’s equations appear are going to be selected and studied more intensely than those which don’t ‘predict gravity’. Thus, the fact that the currently most intensively studied theory has the field equations inside it is not particularly surprising.
The question at hand – whether string theory has earned the attention it has received – is to be decided by asking what predictions it has made which were not simply the reasons for paying attention to it in the first place. The result seems to be that string theory has produced dualities, AdS/CFT and so on, which are interesting, but which don’t actually qualify as experimental predictions.
It seems likely to me that in the distant future, string theory will occupy a position in relation to gauge theories similar to that presently occupied by group theory in relation to quantum mechanics. That is, it will be regarded as an invaluable tool, although it is really a branch of pure mathematics which on its own makes no statement about nature.