The string theory anthropic landscape point of view has now become so widely accepted and entrenched in the particle theory community that various people are making their claims about having had the idea first. The standard first paper that people generally reference is Leonard Susskind’s February 2003 The Anthropic landscape of string theory, which now has 243 citations. Susskind claims credit at least for the “Landscape” terminology in his recent book.
Last month Dutch string theorist Bert Schellekens posted a paper on the arXiv entitled The Landscape “avant la lettre”, in which he claims credit to some extent for the idea. He is quite enthusiastic about the Landscape as a paradigm shift and a new way of doing physics:
… I think even today we are only in an intermediate stage of a very slow shift of opinions regarding the objectives of our field. Although landscape ideas and even the anthropic principle are now at least discussed, it seems to me that the importance of the landscape is still severely underrated. I have tried to express my enthusiasm about the recent progress during seminars, but apparently with little success.
Schellekens claims that:
My own thoughts in this direction started around 1987. The year before I had published a paper with Wolfgang Lerche and Dieter Lust. Like other authors at the time, we found large numbers of four-dimensional chiral string theories, but much more than others we made a point of strongly emphasizing the non-uniqueness of the result.
He goes on to say that already back then it was clear to him that string theory was sending the message “if we find one vacuum we are going to find a huge number of them.” He recalls that when he was working at CERN in the years before 1992 he was promoting the anthropic string theory landscape idea and encountering a lot of resistance, often from people who now tell him that they had always been saying this kind of thing.
In 1998, at the occasion of his inauguration at the University of Nijmegen he gave a speech on this subject in Dutch. In the arXiv preprint Schellekens reproduces the Dutch text of his speech, together with an English translation. He notes that he used the Dutch word “landschap” in the text, although he mostly referred to the landscape using the Dutch word for a “mountain range”.
Schellekens admits that string theory may not be correct, but he says that string theory implies the landscape, so for string theory to be correct the landscape must exist. His only comment indicating that this might be a problem for string theory is that
…the unexpectedly huge size of the landscape is making it a lot harder to convince ourselves of that.[e.g. the correctness of string theory]
He does admit that back in 1998 he expected the size of the landscape to be much smaller than it now appears to be, smaller than the 1080 vacua that, uniformly distributed, could cover all possible values of the standard model parameters to the accuracy that we can measure them. So he expected that one would be able to somehow check string theory by seeing if one of the vacua agreed with the real world. Now that the number of vacua seems to be vastly greater than this, eliminating any reasonable hope of checking string theory this way, for some unfathomable reason his enthusiasm for the idea is undiminished if not intensified.
If you just can’t get enough of landscape discussion, there are recent blog entries on the topic by Sabine Hossenfelder and Alejandro Satz.
Update: The last-gasp hope for getting a prediction out of the landscape is that there is some useful structure in the landscape, so that it doesn’t densely cover all possible standard model parameters. Washington Taylor and Michael Douglas have been looking for such a thing amongst vacua, trying to find some correlations between properties of these vacua. For more about this, see Taylor’s web-page. Lubos has a blog posting about all this, in which Taylor explains the philosophy:
If we find 5 models with features X and Y of the standard model which all have feature Z which is not yet observed it is not very definitive. If we look in different parts of the string theory landscape and find that all 1020 models we know how to construct with features X and Y of the standard model have feature Z also it begins to carry some weight as a possible prediction.
So far, as you might expect, since there is no known reason for such correlations, they haven’t found any. Lubos reports:
Wati’s result in his particular examples was that there was virtually no information in the correlations: the difference was one bit and the distributions of different quantities were essentially independent Gaussians.
and goes on to rant:
Surely the physicists have not been working for 30 years to extract 1 bit of information – whose probability of being correct is moreover 50 percent. Even if there were any correlation, I would probably find such a correlation physically uninteresting. We know for sure that some of these correlations would agree with those observed in the real world, and some of them would not.
What will you do with this probable outcome? Will you overhype the “successful” patterns as evidence that the landscape reasoning is good, while you will be silent about the “unsuccessful” ones? I would count this activity as a part of astrology or catastrophic global warming theory, not physics. It’s frustrating to see that this is what is apparently being intended.
I wonder whether the people who were producing the very convoluted microscopic theories of the luminiferous aether in the 19th century really believed that this was the way to say anything new about physics – or whether most of them did these things just to do something and keep their jobs. Einstein took over in 1905 and showed not only that the aether was a ludicrous fantasy – but moreover, the absence of the aether is one of the basic principles that underlies his relativistic revolution in physics. Today, all of us – except for those in loop quantum gravity – know that the aether is a silliness that is not realized physically and that was never well motivated.
My feeling about the random model building and random model guessing is somewhat analogous to the random construction of the aether from gears and wheels. We’re missing something and we should not fool ourselves into thinking that we’re not.
Update: The Harvard physics department seems to be having quite a few seminars on the Landscape, and one participant reports:
A funny aspect of these discussions is that one can’t quite distinguish which of the considerations are jokes and which of them are meant seriously. At least I can’t distinguish them.
For rational 2D CFT you should assume that space to have discrete topology, if that’s what you are alluding to. The deformation of any rational 2D CFT is non-rational, so all points in the “landscape of rational 2D CFTs” are isolated.
And we do understand what the nature of this space is like. Which of course does not mean we know precisely how to navigate it.
The basic premise of perturbative string theory is that you compute the scattering amplitude for incoming particles a,b,c and outgoing particles c,d,e by computing CFT correlators with insertions being some states corresponding to a,b,c and c,d,e. That’s what I mean.
Urs, but to call something an S-matrix, the least it has to deliver is the validity of cluster properties. Heisenberg’s 1943 proposal failed exactly on this point, the multi-particle scattering amplitudes from his S-operator model did not fulfill the asymptotic multiparticle cluster factorization. Any S-matrix, independent of whether it comes from QFT, string theory or any other physically interpretable particle physics theory, must fulfill this property. For the S-matrices coming from QFT it is easy to see that this property holds.
The other day I was asking for a proof in the setting of string theory and got no answer. Can you give me an answer?
“The other day I was asking for a proof in the setting of string theory and got no answer.”
You got an answer. You just didn’t like it.
The tree level N-particle S-matrix has only simple poles, whose residues are given by products of lower-point tree level S-matrices. At loops, you start getting cuts, and unstable resonances develop finite widths. And, again, in appropriate limits, the g-loop S-matrices factorize onto lower-point (and lower-loop) S-matrices.
All of these reproduce precisely the required analytic properties of the perturbative N-particle S-matrix. And they follow from axiomatic properties of 2D CFT (+ BRST invariance and the Frenkel-Garland-Zuckerman version of the No-Ghost Theorem).
If you find those arguments unsatisfactory, you have a simple opportunity to DISPROVE string theory by finding a counterexample. Compute, say, the 1-loop bosonic string N-particle S-matrix element for some process and show that it fails to have the required properties.
Since you seem to know so much about the subject, that should be easy for you …
And your “insinuation … about the missing autonomous vacuum polarization” makes as little sense now as it did then.
Mentos,
the one-particle structure (residua of poles) are related to the Stueckelberg causal rescattering and I appreciate your remark that there are at least some indications for this kind of timelike macrocausality (no timelike pre-cursors). But it is not addressing the cluster factorisation. And believe me I do not plan any sinister attack on string theory, I genuinely want to know.
Concerning the lack of communication between the different string vacua, I made a suggestion (which, if I would work on string theory I probably could prove, it should not be too difficult to understand the consequences of the absence of direct target vacuum polarizations). But I just do not have enough physical confidence in order to work on problems on which string theorists failed to do their homework. Do you have an argument why against all physical intuition one acquired in particle physics this is so?
And let me add, I do not quite share Peter’s belief that the present crisis can be all blamed on string theory; the latter is rather the most visible sign of a degeneration process in particle physics and a fundamental critique of the present situation must include those developments which prepared the fertile ground for the reception of string theory.
“But it is not addressing the cluster factorisation.”
Aside from the analyticity, crossing, and factorization properties, what property of the S-matrix are you worried about?
“Concerning the lack of communication between the different string vacua,…”
I’m not sure what you mean by that. One of the things KKLT did was estimate the tunnelling rate between the metastable de Sitter vacua they found. They required (among other things) that the lifetime be comparable to or longer than the age of the universe.
For stable (supersymmetric) string vacua, there is, of course, no tunnelling.
But we don’t have to go to string theory to see that you seem to have some confusion on this point.
Consider Seiberg-Witten theory: N=2 supersymmetric SU(2) Yang Mills Theory. This theory has a 1-complex dimensional moduli space of vacua. Is there “communication between the different vacua” in that theory? And, if not, what does that have to do with vacuum polarization?
Now turn on a mass for the adjoint chiral multiplet, breaking N=2 supersymmetry down to N=1. Whereas, formerly, there was a continuous infinity of vacua, now there are just two isolated vacua. Is there “communication between the two vacua” in that theory? And, if not, what does that have to do with vacuum polarization?
One thing I have been wondering about is how much the average string theorist knows about the competeing alternatives. How many have themselves determined that string theory is the most promising approach and how many have simply trusted others opion?
O.K. Mentos,
I think the clustering of the string S-matrix can be achieved by definition. You simply use those pictures of those tubes and define disconnected amplitudes. There is still the problem to show that what you interpret the connected part really goes to zero when the wave packets of the particles become asymptotically spacelike separated. This is indeed a analytic property and what you say about tree diagrams has at least a certain plausibility.
Heisenberg’s S-matrix models where given by a closed operator expression (the exponential of i times an hermitian operator which was a finite power series in free fields). In that case the cluster factorization failed (and probably cannot be obtaines by any such finite series). Lets hope that this will be argued in some future book on string theory but let us not come back to it in this blog.
Concerning the question of vacuum degeneracy you raised, I have no problem of understanding this issue in connection with spontaneaous symmetry breaking. In that case the theory can be decomposed so that the vacuum is unique and all the irreducible components are identical physical theories, i.e. if you have seen one you know them all. The case of the Schwinger-Higgs breaking which may lead to the Theta vacua is similar. In fact whenever you have several translation invariant states (vacua) you can without loss of generality reduce the situation to a theory with a unique vacuum. Is that what you mean “moduli”? This seems to be an expression which comes from a geometrical metaphoric picture of QFT to which I have no intrinsic access. Is there any way to understand this in QFT concepts without referring to big names?
“Concerning the question of vacuum degeneracy you raised, I have no problem of understanding this issue in connection with spontaneaous symmetry breaking.”
No.
In the Seiberg-Witten example, the different vacua corresponding to different points in the u-plane are inequivalent. This is not like spontaneous symmetry-breaking, where all of the vacua lead to equivalent physics.
“Is there any way to understand this in QFT concepts without referring to big names?”
You could start by reading their paper, where they solve the low-energy dynamics of this QFT. Or one of the many good reviews on the subject (which, of course, has many generalizations to other gauge groups and the addition of matter hypermultiplets in various representations of the gauge group).
Lubos:
Most of us are also familiar with the view you have expressed (Feynman was a proponent, maybe you got it from him, I don’t know) that the mathematics — or the equations — are the full story. Einstein would probably not have believed this view.
Feynman also shares your disdain for hidden variables. (cf. Vol 3, Feynman Lectures, page 1-10 “Suppose we were to assume that inside the electron, there is some kind of machinary that determines where it is going to end up” etc)
However, you better be pretty sure that Feynman (or whoever it was you read or heard these ideas from) is actually right before you subscribe such absolute certaintity to these views, or as a scientitst, you may find that you miss out on some very interesting possible theories…just because you stopped looking deeper.
T’ Hooft just 2 weeks ago published a very elegant hidden variable theory :
http://www.arxiv.org/quant-ph/0604008
Perhaps you can explain to T’ Hooft that he is a crackpot…
Anyway Lubos, you will never become a physicist until you start to think for yourself.
Before I retire for today one last question which originates in Urs’s claims.
On classyifying 2-dim QFT one certainly can have different settings. My favorite one is the theorem (Guido-Longo-Wiesbrock math-ph/9703129) that the physical classification of chiral conformal QFT (including the localizable “meat” and not just the topological “bones” and also not only the rational ones) is
“isomorphic to the isomorphism classes of standard modular inclusions” (modular in the sense of Tomita-Takesaki modular theory and not in the sense of modular forms), the latter being a clealy defined mathematical problem.
Your Frobenius algebra classification may achieve the same thing. But I fail to see any indication of a unifying universal “space”. Are you thinking of an analogon of a regular representation for compact groups? What brings an expert of classification of chiral theories to believing in the existence of such a universal object? Please help me, I am completely lost.
LDM,
Please discuss Lubos’s views about things like hidden variables that have nothing to do with the posting with him over at his blog, not here.
Woit,
If one cannot have some reasonable freedom to discuss or intelligently pursue the ideas that are naturally part of a discussion or blog… because it is not exactly coincident with the original posting…well, it seems like an artificial restriction…but then again, it is your blog, and you can enforce any policies you like.
I will therefore honor your request and not be posting further on your site.
Lubos has a hilarious account of a talk on the landscape by Vilenkin at Harvard.
Lubos:”Vilenkin said that by this single sentence, Nima has essentially scooped the speaker and presented the rest of the talk as Vilenkin planned it.”
Vilenkin and Nima sound like two naked emperors flattering each other. “Nima, your new garments look so good on you”. “Yours do too, Vilenkin”
Peter, I am sympathetic to your concerns, that string theory suffers from problems, such as extracting predictions, and that too much of particle physics has been engrossed in this seemingly unpromising approach, but I am curious as to what research programs particle physicists and theoretical particle physics are pursuing that go beyond the standard model, but do not involve SUSY or string theory or higher dimensions, programs that are academic respectable, and not “crackpots”. by “beyond the standard model” one example is what sort of unification do you prefer, as SUSY-string theory approach you reject, and other models, such as SU(5) which predict proton decay and magnetic monopoles, seemingly is contradicted by experiment and observation. other examples of going beyond the standard model might be predictions for high-energy physics, dark matter candidates, etc. do you think the graviton is a part of particle physics and if so, what are non-string methods of studying it?
“string theory is absolutely essential for any conceptual theoretical physics beyond the framework of quantum field theory”
“quantum gravity can’t be done without string theory.”
Lubos, can you post (or link to) some justification of these assertions — in terms that a typical physics grad student (not in high energy) could understand? Or is that impossible?
I don’t have a dog in this fight, but so far in this discussion I haven’t seen any justification for these claims — just the assertion that they’re obvious.
To Thomas Larsson: LHC can kill more than supersymmetry; it can disproof the theoretical prejudice that the SM must be replaced by a theory that makes the Higgs mass naturally small. If LHC does so, some people will still study supersymetry, but no longer as a solution to the hierarchy problem.
Hopefully this will be faster than in the analogous case of the aether: one century ago there were no blogs ranting that ether dragging is not even wrong. (Sorry for having used the word aether)
I believe that W Taylor’s attempts to extract information from the Landscape goes against the general picture that’s very naturally emerging from string theory, namely that string theory makes no predictions at all.
tsg,
Since Lubos can’t or won’t give a link to back up his assertion “quantum gravity can’t be done without string theory,” can I suggest he is referring to:
http://arxiv.org/abs/physics/0601218
Hope this is useful. 😉 Also, I want to say Peter is not trying to replace you with a crackpot, Lubos! He is just trying to stop you being one to save you wasting your life on pseudoscience. The same goes for other string theorists. 🙂
tsg,
Jacques Distler wrote a nice post about the difficulties of quantum gravity a while back:
http://golem.ph.utexas.edu/~distler/blog/archives/000639.html
I’m not sure it meets your criterion “a typical physics grad student (not in high energy) could understand”; the requirement is that you at least understand the renormalization group.
The Reuter approach to QG, looking for a UV fixed point, makes sense from this point of view but is really difficult. I have no idea how LQG fits into this story.
knotted string:
Somehow, I doubt Lubos was referring to a crackpot paper on the physics arxiv.
tsg:
Distler’s post is better, and he has another one where he discusses Reuter et al (maybe the best hope for a quantum field theoretic approach to QG).
Bert Schroer wrote (in http://www.math.columbia.edu/~woit/wordpress/?p=392#comment-10888)
From the way the question is stated it seems to me that there is some sort of misunderstanding involved.
The theorem I was referring to says that a full rational 2D CFT is the same thing as a special symmetric Frobenius algebra object internal to the representation category of a chiral vertex algebra.
The claim is that this is the complete solution of the problem of solving the sewing constraints, given any chiral algebra and the spaces of conformal blocks obtained from these.
So, to say that again, the “space of rational 2D CFTs” is precisely the space of Morita classes of algebras internal to modular tensor categories. Since every perturbation of rational theories leads to a
a non-rational theory all the points in this space are isolated.
Therefore, as long as we are not talking about moduli stacks of RCFTs, we can pretty much think “set” instead of “space” here.
I have a more detailed discussion of the FRS theorem here:
http://golem.ph.utexas.edu/string/archives/000813.html
Dear Peter,
If i can return this thread to its original subject, the earliest discussion of a crisis in predictibility from a vast proliferation of string vacua that I am aware of is in the conclusion of a 1986 paper by Strominger, in which he says, in part
“the class of supersymmetric superstring compactifications has been enormously enlarged…..it does not seem likely that [these] solutions……can be classified in the foreseeable future. … All predictive power seems to have been lost.”
– A. Strominger, “Superstrings with Torsion,” Nuclear Physics B, 274(2):253-284 (1986).
This is a highly cited paper, which makes it curious that its main conclusion was ignored.
As far as the concept and the term of a landscape of theories, to my knowledge, they originated in my papers in the 1990’s on cosmological natural selection, and my 1997 book, Life of the Cosmos. For example gr-qc/9505022 and Classical and Quantum Gravity 9 (1992) 173-191. I do not take credit for the anthropic version, the whole point of my idea was to solve the crisis of too many string vacua that was apparent already then by inventing a falsifiable scenario that avioded the anthropic principle (which it was clear then could only lead to a dead end.) I chose the term “landscape” to allude to the well known biological term “fitness landscape” in order to make the point that the resolution of the crisis has to follow the methology used in biology-of being based on a mechanism that makes our universe a typical member of the ensemble- if it were to be testible scientifically. I find it bizzare that people have taken the term, and used it both without proper attribution and without recognition of its connotations-which were exactly to avoid the use of the anthropic argument.
Thanks,
Lee
Two comments:
In an early discussion on sps, before that newsgroup effectively died, Wolfgang Lerche also seemed to claim anthropic credit for the Lerche-Lust-Schellenkens papers from around 1987.
I read a preprint by Schellenkens in the early 1990s, maybe on Leech or Nijmeier lattices, whose beginning I still remember (roughly): “It is clear that string theory contains all of mathematics. The only question is whether it also contains all of physics.” Positively Motlerian.
Didn’t you know, Lee?… the landscape is now synonymous with the anthropic principle and has been ever since Lenny’s book came out.
Lumo:
At any rate, I don’t think that the originator of the anthropic idea has anything to be proud about…
Duh… that would be, Brandon Carter, after a bunch of respectable physicists independently came to a similar conclusion after running into the same brick wall that stops science dead in it’s tracks to this day…
OHhhhhhhh… you meant the Stringy Anthropic Landscape Principle… Sorry, I forgot that you take string theory for granted without justification, like any good crackpot would.
~
Thankyou, Lee… I thought that I was going to burst…
It seems that these days the priority fights in particle physics are increasing in intensity the closer they are to trash-cans. Its pathetic!
It would be interesting to see if there were other episodes in physics history, where there were heated priority fights over a “trash can”.
Funny, just before reading the above I was tossing around this image in my head of Susskind and Schellekens as two bums fighting over a cardboard box.
>Funny, just before reading the above I was tossing around this image in my head of Susskind and Schellekens as two bums fighting over a cardboard box.
Funny, really, that a bunch of people with little or no awareness or appreciation of his many contributions to physics (Kogut-Susskind fermions, technicolor, the Fischler-Susskind mechanism, black hole complementarity, the holographic principle, Matrix Theory, …) should be busying themselves making fun of Susskind.
Pretty much sums up everything wrong with so-called “physics blogs.”
Lubos Motl wrote:
“Could you also find a technical problem with any of the 4000 papers that show that your idea is an undefendable one?”
Science is not a democracy, the laws of nature are not determined by popular vote.
These arguments about string theory are no different than the arguments of warring priest during the Reformation and Counter-Reformation.
With string theory I predict that we’re seeing the birth of a new type of religion,
a meta-mathetical theology.
Lubos and Peter,
it’s amusing how you both rush headfirst into infantile disputes about web statistics when about 99.95% of the web fares better than both of your sites combined. Seriously, how can you call yourselves scientists and willingly engage in these childish internet shenanigans? Have you no shame or common sense? Shouldn’t you be spending your time more productively, like on your research? Do yourselves a favor and unplug your internet connection for like a week and see how much work you can get done. Who knows, you might even fix string theory or show that it has an ounce of predictive value.
” ‘Could you also find a technical problem with any of the 4000 papers that show that your idea is an undefendable one?’
Science is not a democracy, the laws of nature determined by popular vote. ”
No, it’s not.
Nor does it amount to mere he said/she said.
Do you have a single rational argument why Maldacena/Witten/Gubser-Klebanov-Polyakov and all of the various people who have checked, rechecked, generalized and extended their calculations are wrong and Bert Schroer is right?
This isn’t about a head count. It’s about the results of detailed calculations (by a host of very smart people).
Why don’t you sit down with Berenstein, Maldacena and Nastase’s paper (for instance), and figure out where the flaw is. That might give a little bit more force to your argument.
Mateos:
“Consider Seiberg-Witten theory: N=2 supersymmetric SU(2) Yang Mills Theory. This theory has a 1-complex dimensional moduli space of vacua. Is there “communication between the different vacua” in that theory?”
..
“Why don’t you sit down with Berenstein, Maldacena and Nastase’s paper (for instance), and figure out where the flaw is.”
The kind of people you try to argue against here would not accept SYM as well-defined theory to start with. They even do not consider QCD as a well-defined or meaningful theory. It is completely pointless to fight with them about string theory – they are against everything that has happened after their own PhD thesis in the 50’s. They use this silly anti-string club here as a platform to propagate their dislike of what they since ever failed to grasp.
Fortunately, no serious researcher cares about this; the Standard Model has been developed irrespective of all objections by constructive field theorists, a (incompletely understood) theory of quantum gravity has been discovered that has lead to deep and far-reaching insights in black holes, and that has lead to surprises such as the AdS/CFT Correspondence. While one sort of people waste their time agonizing why all of this must be wrong, others just sit down and do the hard work, trying to improve our understanding.
“The kind of people you try to argue against here would not accept SYM as well-defined theory to start with. They even do not consider QCD as a well-defined or meaningful theory. It is completely pointless to fight with them about string theory – they are against everything that has happened after their own PhD thesis in the 50’s.”
Which lead one to wonder why Peter (who, otherwise, seems desperate to be taken seriously) is so eager to promote their cause.
T’ Hooft just 2 weeks ago published a very elegant hidden variable theory :
http://www.arxiv.org/quant-ph/0604008
Perhaps you can explain to T’ Hooft that he is a crackpot…
LDM, ‘t Hooft is undoubtedly aware that his position on Planck-scale determinism is very controversial, and that anybody talking about hidden variables without being a Nobel laureate would immediately receive 10 crackpoints for
“9 .10 points for each claim that quantum mechanics is fundamentally misguided (without good evidence). .
I was first quite bemused about ‘t Hooft’s position, but then I realized that his motivation was to combine background independence with locality; this is a serious problem, because there are no local observables in conventional quantum gravity. This motivation makes a lot of sense to me, but I still think that ‘t Hooft is wrong. This is because there is another way to combine locality with diffeomorphism symmetry, which involves observer dependence and diff anomalies.
MoveOnOrStayBehind & Mentos,
You people are missing the point, perhaps deliberately. Neither Peter nor the majority of the “silly anti-string club” here are saying that Superstring theory should be abandoned. It is a possible approach. We just think that the effort expended on this quest is disproportionate to the results obtained and it is high time that more effort is devoted to alternatives rather than propping up this failed project. A bit more honesty from the Superstring community would help. If after more than 20 years of effort you cannot calculate cross sections then either (i) you should stop calling what you are doing physics or (ii) you should give it up. I doubt very much if Peter or the rest of us “silly” anti-stringers would have a problem with 10% of the current Superstring community carrying on on the basis of option (i), but to have almost all alternative strategies squeezed out of theoretical physics just because the majority are embarked on this Mission from some 10/11-dimensional God is not acceptable, and none of us are going to shut up about it until the balance is redressed in favour of that which looks more like empirical science.
The whole research process is much more haphazard than you people would like to believe. Whilst I cannot say that I would necessarily bet my life on Schroer’s algebraic field theory or Peter’s geometric quantization delivering the goods (any more than they would bet on my pet projects), I am happy for them to keep working on these and accept the possibility that one or other of them will be right and I wrong. I don’t feel threatened by them and I don’t feel that I have to subscribe to either of their approaches because of peer pressure. This is the way it should be, but then I am not in a position where I need anyone in the academic establishment to like me. For those that do need acceptance, the system at the moment is set up to force them to follow directions they do not necessarily want to go in just because of the unwholesome domination of one particular line of enquiry. This is not good for the subject.
” ‘Could you also find a technical problem with any of the 4000 papers that show that your idea is an undefendable one?’
Science is not a democracy, the laws of nature determined by popular vote. ”
No, it’s not.
Nor does it amount to mere he said/she said.
“Do you have a single rational argument why Maldacena/Witten/Gubser-Klebanov-Polyakov and all of the various people who have checked, rechecked, generalized and extended their calculations are wrong and Bert Schroer is right?”
Sure. Can you point to a single testable prediction about our physical universe to come out of “Maldacena/Witten/Gubser-Klebanov-Polyakov” et al. Otherwise it’s just a lot of mathematical masturbation by some (admittedly clever) people, but that’s all it is.
That the real problem and issue that physicists has with string meta-theory.
Not whether someone’s calcualtions are “right”.
Once again that level of discussion here brings Kissenger’s bon mot to mind.
“Why are academic debates so fierce, nasty and bitter?”
“Because the stakes are so low.”
“The kind of people you try to argue against here would not accept SYM as well-defined theory to start with. They even do not consider QCD as a well-defined or meaningful theory. It is completely pointless to fight with them about string theory – they are against everything that has happened after their own PhD thesis in the 50’s.”
This type of lame argument is know as the “straw man” argument – attributing statements and views/attributes to the other side that they did not make/have to begin with and then arguing against them.
The childness of the debate here, comparing the number and ID of IP addresses, the ad hominem personal attacks, etc. is symptomatic of how this field has degenerated in the absence of experimental data.
Despite the religious type claims by the string theorist that string meta-theory is the only possible way, the space all possible models is probably infinite and without experiments based in physical reality to kill off the incorrect models, the probability of any one approach is being right approaches 1/infinity.
Many of these approaches may lead to interesting math, but without testable predicitions, it’s not physics,
despite what any “authority figure” in the field may claim.
Mentos,
there is a deep misunderstanding on your part of the motives behind my critical remarks. I would be the first to uphold the right of Maldacena to write a speculative paper on an interesting subject; speculative freedom is an essential ingredients of theoretical physics.
What worries me is the apparent misunderstanding of thousands of his colleagues who completely ignore that
(a) there exists a general relation between CFT and AdS (a structural rigorous mathematical theorem of the kind you seem to be so afraid of, already in Fronsdal´s early work you find indications), it is a kind of different re-packing a la Christo of the same physical substance (if this helps to raise your awareness)
(b) there is absolutely no reason whatsoever to think that SUSY with beta=0 (the prerequisite for conformal invariance) is distinguished by its conformal invariance from infinitely many yet nameless other 4-dim. CQFTs; the conformal richness is not limited to low dimensions
These two points require to view Maldacena´s conjecture within a wider context since all conformal models possess a AdS re-packing and they are all potentially interesting. What I am saying is not new and can be found in the literature; but particle physics has been distorted by very unfortunate sociological developments and either people are not capable any more to see this or are afraid not to collect enough impact points if they are leaving the path of lemmings.
The most important ability of a theoretical physicist (totally different from a mathematician) is that he learns to live with halftruths in an imperfect world but without ever forgetting that the main aim is to make it more perfect.
Certainly when some mathematical physicist say that QED does not exist, this should not be interpreted naively. What it means is that our most successful theoretical Ansatz is not yet conceptually secured. The old Bohr-Sommerfeld QT was also quite successful, but just imagine what would have happened to physics if people would have been as complacent as they seem to be nowadays those which get into these semantic arguments with respect to those colleagues who point out that we (this includes QFT in its present state) live in a provisorial situation. In contrast to all other branches of physics which have been conceptually secured (e.g. by nontrivial examples), QFT and even more so string theory is still conceptually totally unsecured territory.
It was a blessing that the step from old to modern quantum mechanics took place within auch a short time; imagine the confusion it would have created und the many holy cows (like the above one) it would had led to, if several generation would have stepped on the old ideas and in this way solidified them?
Maybe Schellekens thinks of this paper here
http://ccdb4fs.kek.jp/cgi-bin/img/allpdf?198612321
Together with luest, written in 1986.
There, Luest who is now in Munich and Schellekens write
“It seems that not much is left from the celebrated uniqueness of String theory”.
The paper is from November 1986.
> We just think that the effort expended on this quest is disproportionate to the results obtained and it is high time that more effort is devoted to alternatives rather than propping up this failed project.
I never understood this argument.
Nobody prevents you, Peter, Lee, etc. to work on alternatives.
The internet even makes it zero cost to publish, promote and discuss such ideas and theories.
Do you suggest some sort of committee to determine who should work on what idea?
When significant professors allegedly say “string theory is the only game in town”, then, Wolfgang, what happens to the likelihood of a student to do something else? You may address this in either frequentist or Bayesian terms 🙂
No Wolfgang, things do not work in your simple-minded and probably honest way. Peter and other critical minds are too old and lack the stamina which you need to persue new innovative ideas. Their (and also my) accumulated insight and critical mind has left them with the necessary distance and enhanced power seeing through smoke screens and selfdilusions. It is a bit like the trainers in football, you probably would not suggest that they return as active players.
The people who (through distributions if impact credits) could have an influence on the present situation are the ones who are administering the present crisis e.g. in the editorial boards of new HEP journals and this is the best guaranty that particle physics will continue the same route for the next decades as it has done in the past two decades. If some novice has the intellectual capabilities and the courage to make a deep investment outside the prescribed line, he will pretty soon lose his material support; I have seen several such cases and I know what I am talking about.
NaNL said:
“Sure. Can you point to a single testable prediction about our physical universe to come out of “Maldacena/Witten/Gubser-Klebanov-Polyakov” et al.”
One?
OK. How about the prediction (by Kovtun, Son and Starinets) that the ratio of shear viscosity to entropy density in the quark gluon plasma is 1/4pi (plus computable corrections). No other model, nor any known material substance has so low a ratio. But it’s in good agreement with what’s measured at RHIC.
There’s more (lots more) one could say about the importance of AdS/CFT. But you asked for ONE prediction. So that’s what I’ll give you.
Schroer said:
“These two points require to view Maldacena´s conjecture within a wider context since all conformal models possess a AdS re-packing and they are all potentially interesting.”
You’re joking, right? There’s a huge industry finding supergravity duals to other 4D field theories (both conformal and nonconformal).
But, as always, the dual of a 4D ( C )QFT on the boundary is a gravitational theory in the bulk of AdS. The claim that one gets another (nongravitational) QFT in the bulk is just wrong.
“Certainly when some mathematical physicist say that QED does not exist, this should not be interpreted naively. What it means is that our most successful theoretical Ansatz is not yet conceptually secured.”
Not to anyone who has assimilated the lessons of Ken Wilson, Steve Weinberg and others.
It means that QED is an effective field theory, valid at low energies, but which must be replaced by some other, better-behaved effective theory at higher energies. (As, of course, happens in the real world.)
In another thread, you professed to take a Wilsonian attitude to QFT. But every off-hand comment of yours indicates that you really don’t believe the central lessons that Wilson taught us about QFT.
Mentos
I do believe the central lesson of Wilsonism but I do not think that he ever claimed to prove the existence of a consistent mathematical theory behind those ideas (existence of QED,…) and computations which come to our mind when we look intensly at a Euclidean action as a definition of a model. The word Wilsonian stands for me also for non-metaphoric and non messianic (i.e. far away from a final theory of everything), a meaning which you do not seem to share).
Concerning the various SUSY models I just counted them summarily as one (if you have seen one, you know them all). But if, as you seem to alledge, every of these expected infinitely many different families (which I had in mind) has also a corresponding gravity AdS (by that rather simple Christo-type of repacking, the only real nontrivial case which deserves the name holography is holography on Nullsurfaces) then I find this totally generic terminology “gravity” quite empty and uninteresting, despite the big names with which you all the time seem to try to create the feeling of awe.
“then I find this totally generic terminology “gravity” quite empty and uninteresting,”
No, it’s the heart of the matter.
The most basic statement in the AdS/CFT correspondence is that, to every local operator in the boundary ( C)QFT, there corresponds a field in the bulk AdS. Now, one of the hallmarks of QFT is the existence of a local, conserved stress tensor.
Can you guess what field that corresponds to in the bulk AdS theory?
“I do believe the central lesson of Wilsonism.”
Perhaps I should ask, “What lesson is that?”
Wolfgang,
Sure, Lee and I can work on what we want to work on, but science is a collective enterprise, and it is far more difficult to make progress on a problem if you are the only one working on it.
There already are committees established that decide who should work on what idea. They’re called hiring committees and I’ve sat on them. One of the main things hiring committees look at is the subject potential hires are working on: is it a “hot” subject the department wants to be a piece of? Many hiring committees are working with explicit guidance as to what ideas the person they will give a job to should be working on. I could go on about this, but for examples, you should consult Lee Smolin, who can give you numbers about how many academic institutions in the US over the last 20 years have been willing to even consider hiring somebody working on ideas about quantum gravity that are not string theory. I gather his forthcoming book has a lot more about this.
Prof. Schroer, Arun, Peter,
I guess we can agree on the following:
i) quite a substantial amount of effort and resources has been spent already on quantum gravity outside of string theory. It is safe to assume that this will continue. Just check the gr-qc section on the arXiv.
ii) If somebody wants to write a thesis about LQG, lattice gravity, or whatever he/she will not have a problem to find an advisor.
iii) There is certainly a difference in funding for string theory vs. other approaches, which is easily explained by the simple fact that string theory was and still is the most promising approach so far.
But none of this has anything to do with my point, which is that students, postdocs, professors etc. are free to explore whatever they want. I am sure each one of them will try to optimize his/her own risk/reward ratio. If you are a “low-risk person” use the main road (string theory), if you are a “longshot person” try causal sets, algebraic qft, LQG, etc.
Mentos,
I am sorry, but if such a simple re-packing (a change of the spacetime encoding of any algebraic substrate which was given in the conformal spacetime organization and which is being equipped with a different AdS one) as the one from an AdS to its asymptotic timelike brane (trivial because it keeps all the symmetries and modulo some simple amendments also the causal structure (which a holography onto a Null-horizon definitely does not maintain!!)) creates inexorably something which you generically call “gravity” then you have ruined the magic which many people still expect behind Maldacena, and I wash my hands free of guilt.
Wilsonism to me means that I do not have to know all the world (to the Planck length and beyond), rather I am able to make a conceptually closed theory in the present situation of QFT (and, if I am allowed to add this, also a mathematically controllable one) which is free of cutoffs and elementary length.
To Wolfgang,
on the whole I agree, but let me point out to you in all modesty that somebody (who collaborated with me) who has done the pioneering work on modular operator theory on which the ball of QFT got rolling again (and something you probably will notice in the near future) had no career chance against any second rate string theorists. Since you seem to be a string theorist, you probably only see those in the present light and not those in the dark.