Gosh, a thoughtfully-written general level (more or less) article on some of the general outcomes of string theory research! It’s written by Matthew Chalmers, and is in the Sept. ’07 edition of Physics World*. The article can be read online here, and downloadable pdf is here. The graphic on the right came with the article. I don’t fully understand what it is, but the title, like that of the article, is “stringscape”… Look, let’s not over-think this cvj – it’s a pretty decoration.
I’ve done a quick read of it (should re-read more carefully later on – it will no doubt have some emphases with which I disagree somewhat**) and I’d say it is very much worth reading. While not a perfect summary (what is?), compared to a lot that’s been out there, you’ll find it rather more informed, less sensational, (refreshingly unpoisoned by various prejudices, such as the presentations of Smolin and Woit – see numerous earlier discussions in the “More Scenes from the Storm in a Teacup” series of posts, and others), and unafraid to go to some length to unpack the issues somewhat carefully.
Very importantly, it contains numerous quotes from various respected researchers in physics (some working on string theory and some not), and it is good to read to get a sense of the layers of views that prevail- contrasting, disagreeing, agreeing, hopeful, pessimistic, doubtful, optimistic – and the focus is the science, not sociology. Such a diversity of views, with a prevailing pragmatism (i.e.: “we’ll work on whatever good idea helps us make progress, strings or not strings”), is present in any healthy scientific endeavour, at any point in history.
As far as I can see, the short summary of the summary seems to be what I’ve been saying time and again here (but read it yourself for some of the reasons why, and maybe also to come up with your own summary, which could well differ from mine):
Will it tell us important new things about nature? It’s a work in progress – Too soon to tell.
(I should add, as usual: …And in the meantime we’re learning so much from it, shaping useful tools with many potential applications, and training so many young people in important techniques from all over physics and mathematics… etc, etc.,…)
Enjoy!
-cvj
___________________________________________________________________________________
*Thanks Oliver! (It’s been out for a while, and I completely missed it!)
** For example, I don’t agree that “most string theorists think […] that it is only a matter of time before the gravity `dual’ of real-world QCD is worked out”. The issue is much more interesting and subtle than this. See my thoughts about this issue here.
In fact, after a bit of thought, I’ve decided that maybe this is a good sign that it is time to close this discussion thread. I don’t normally do this, but it seems like the right thing to do.
So thanks everyone for reading and contributing to the discussion.
See you all next time, when we will no doubt repeat our arguments all over again, as though this thread never happened….
Cheers,
-cvj
Anomalous Cowherd: – Spot on! Physics is one of those profound human activities that is about collective effort that should cut across issues of nationality, gender, race, religion, and so forth. I’d say that about Science in general in fact.
Trying to derail some physics discussions to focus on a very poor and highly selective reading of the history of the subject (and the achievements therein) seems, indeed, mean-spirited. There’s been enough mean-spiritedness in this thread already, and we don’t need a nationalistic flavour to be added. I was hoping my attempt at humour in my previous comment would have helped diffuse it, but I was wrong.
So could I firmly request that we get away from this very silly argument and try to be a bit more constructive?
Thanks.
-cvj
Anomalous Cowherd wrote:
Hear hear! Let’s leave the “my team is best” claims to the world of sports.
To andy, Anonamous hero, Tony Smith and Moveon
Why are you guys starting a flame war based on nationality? Over the last century there have been truly great contributions to physics from Europeans, North Americans, Russians, Asians, Africans, South Americans and Antipodeans. I have colleagues from all over the world whom I admire and respect. Physics is something that brings us together, not something that divides us. Why would you start such a mean spirited argument?
145 – Joseph Conlon
Dear Dr. Conlon
Thank you for the helpful comments on your work. It’s nice to see people work through classes of models with the care that you and Fernando have taken. Keep up the good work!
With regard to statistics/counting arguments, I must say that they make me rather queasy. It’s far from clear to me at the present time [maybe this is just a statement of my ignorance] whether the most generic sources of low-energy supersymmetry breaking should be sought in geometric effects [volume effects or warping], or in non-perturbative field/string effects [gauge instantons, Euclidean D-brane instantons, metastable vacua at strong coupling a la ISS, et cetera]. Until we get good studies [such as the ones that you and Fernando have done on your large volume compactifications] on a broad range of constructions I think that this will largely remain an open question. I also have misgivings about statistics arguments in an infinitely self-reproducing multiverse due the the [general coordinate invariance] gauge dependence inherent in the constant time hypersurface slicing on super-horizon scales.
Dear Moveon,
One of the damages Nazi regime produced in Europe is the moving of the greatest physicists from Europe to USA. So, today physics speaks english, no more german.
I think that situation in physics today is due the way someone thinks about such science fiction that easily can excite not well aware people to give funds to academia. This is true vandalism.
Andy
@149 “There is a lot of science fiction that USA leaded research has produced: Multiverse, time machines, wormholes… ”
What a nonsense. Just check the Nobel prizes. Name me one important thing what has come out from fundamental physics research eg from Germany in the last 60 years. And I would say part of the reason is the attitude of people like you.
@150 “pressure forcing CERN to terminate its EXT preprint service”
Again what a nonsense.. as I happen to know first-hand, the people of the library took down this service because of constant misuse by crackpots. Another example how an inititally good idea has been destroyed by vandals. The internet is full of them.
Of course, this will all be moot when, for environmental and other reasons, we move to doing only unleaded physics.
-cvj
Dear Anonymous hero,
I think I should thank you for informing about my not proper correct english. I do not do that rather I see the poverty of your arguments. Grammatics or spelling are not answers. Sorry.
Your views about the peer-review system are rather naive. There is no serious technical control on papers unless they belong to the proper turf. Also in this case the control is rather sloppy.
Anyhow, having seen how sound are your arguments (spelling and grammatics) I am almost convinced that American “leaded” literature should have no problems for the future. I also appreciate American “leaded” movies. In this case too spelling and grammatics are relevant.
Good luck for supersimmetry at LHC. Otherwise I think that American “leaded” physics will be remembered for the greatest fiasco in the history. And I think you should not feel upset if someone will be laughing at you and your dear fellows then.
Andy
Dear Andy,
a correct theory can never stop being rubbish because of experiments: experiments only inform researchers about the validity of a theory but any theory is either valid and valuable or invalid and worthless before the experiments are performed which is why your musings about the LHC, supersymmetry, and string theory are lay misconceptions.
Supersymmetry is spelled with ‘i’, not ‘y’ and the adjective ‘Japanese’ is capitalized. In the process of renormalization, infinities are not ‘swept under cover’ or ‘the rug’ but rather properly evaluated to obtain meaningful and accurate physical predictions and these predictions obtained from the formally infinite integrals are as important for physics as the simple predictions that don’t require any renormalization which is not the only reason why the Nobel prize for Feynman, Schwinger, and Tomonaga was one of the most deserved Nobel prizes for one of the most important discoveries in physics. In Feynman’s case, this discovery was surely not the only one and the path integral approach to quantum mechanics is a great gift of the U.S.-led physics, too.
Renormalization and renormalization group, other mostly American discoveries, are considered to be the most important developments of the last 60 years by many physicists and you haven’t mentioned these notions at all.
‘USA leaded’ should be ‘U.S.-led’ because ‘USA leaded’ is broken English. Time machines and wormholes are speculative and probably unphysical solutions of general relativity that are, by the way, studied uniformly in the whole world, not just the U.S., while the multiverse is no fiction but rather the correct explanation for the cosmological constant according to a significant portion of top contemporary physicists.
Publication of articles is decided by their being correct and articles are attractive or less attractive according to the power of their content, not fashions. Gauge theories might be considered to be a mere technical development in comparison with relativity and quantum mechanics but they are extremely important technical developments anyway.
Cheers
Anonymous hero
Anonymous hero (147), replying to Andy (144), said “… the US-led physics has also given the world of theoretical physics the following things:
the QED including quantum corrections,
perturbative renormalizations,
electroweak theory … ,
quantum chromodynamics … ,
supersymmetry …”.
With respect to QED, Andy (149) noted “… Tomonaga was Japanese … QED was already known … by European researchers …”.
According to the book “The Second Creation” by Crease and Mann (revised edition, Rutgers 1996), (Swiss) E. C. G. Stueckelberg “… apparently wrote up a lengthy paper – in English, for once – that outlined a complete and correct description of the renormalization procedure for quantum electrodynamics. Sometime in 1942 or 1943, he apparently mailed it to the Physical Review. It was rejected. “They said it was not a paper, it was a program, an outline, a proposal,” Stueckelberg remembered. …”.
According to the book “The Beat of a Different Drum: The Life and Sciece of Richard Feynman”, by Jagdish Mehra (Oxford 1994), “… [ Richard Feynman won ] … the Nobel Prize in phyiscs for 1965, jointly with Julian Schwinger of Harvard and Sin-Itiro Tomonoga of Japan … After the Nobel award ceremonies … Feynman went to … CERN … to give a lecture. … Feynman’s lecture at CERN was attended by Ernst C. G. Stueckelberg … After the lecture, Stueckelberg was making his way out alone … from the CERN ampitheatre, when Feynman – surrounded by admirers – made the remark:
“He [ Stueckelberg ] did the work and walks alone toward the sunset; and, here I [ Feynman ] am, covered in all the glory, which rightfully should be his!” … “.
With respect to renormalization, according to the book “The Second Creation” by Crease and Mann (revised edition, Rutgers 1996), E. C. G. Stueckelberg “… [ with ] his student, Andre Petermann, invented … 1951 … the renormalization group, which is now essential to the construction of grand unified theories …”.
With respect to electroweak theory, (Dutch) ‘t Hooft made the crucial proof of renormalizability. According to the book “The Second Creation” by Crease and Mann (revised edition, Rutgers 1996), “… To Stephen Weinberg, ‘t Hooft’s proof just seemed like hand-waving. Then he heard that his friend , the Korean-American physicist Benjamin Lee was working on it. … Working on the problem himself, he [Weinberg] slowly grasped … his old SU2)xU(1) model. …”.
With respect to quantum chromodynamics, ‘t Hooft had the crucial insight of asymptotic freedom. According to the book “The Second Creation” by Crease and Mann (revised edition, Rutgers 1996), “… In June of 1972, ‘t Hooft attended a congress on gauge theories in Marseille … ‘t Hooft got up and announced that he had done the requisite calculations, and that Yang-Mills heories could have a negative coupling constant … to be asymptotically free …”.
With respect to supersymmetry, would the USA look good by taking credit for something for which there is zero experimental evidence, despite many years of explicit searching ?
Some other things:
Three-generation quark mixing was done by (Japanese) Kobayashi and Maskawa.
Independent alternative approaches to USA superstring dogma are attacked and suppressed in the USA (including blacklisting by the USA Cornell arXiv and pressure forcing CERN to terminate its EXT preprint service). Suppressed ideas include, but are not limited to, work motivated by (but not identical to) (Swiss) Armand Wyler’s approach to calculating force strengths.
Tony Smith
Dear Anonymous hero,
String theory is rubbish until we can see some experimental verifications. Not in sight. I hope for you and your friends that people at LHC will find at least supersimmetry. Otherwise you and your fellows will have wasted all your time that would have been better used otherwise, the same for funds.
QED was already known before WWII formulated by European researchers (please check Fermi lectures at Ann Harbor published on RMP). Feynman and Schwinger just invented a way to put infinities under the cover. Tomonaga was japanese.
Standard model cannot be seen as a true revolution, not as relativity and quantum mechanics at least. You are already looking for a way to supersede it. Supersimmetry has not been seen yet. You cannot put it in the list. Not yet.
There is a lot of science fiction that USA leaded research has produced: Multiverse, time machines, wormholes… Besides some freedom in research is going progressively degrading being superseded by what should collect more money in a faster time for academia. Fashions can decide about publication and a lot of meaningless papers appear in the most important journals. There is enough to be tired of this situation.
Relativity and quantum theory still stand there untouched.
Andy
Dear Eric,
Yes, I agree with you (and did say) that non-perturbative effects could violate perturbative baryon number violation. To do this check is model-dependent. However, it changes the dimensional estimate for the proton lifetime suppression from 1/M_string^2 (or whatever power applies) to 1/M_string^2 times e^{-something}
So as long as e^{-something} is small, the proton is sufficiently long lived.
Best wishes
Joe
Dear Andy,
if string theory were the only thing that the US-led physics gave to the mankind, it would already be comparable to relativity or quantum theory. But the US-led physics has also given the world of theoretical physics the following things: the QED including quantum corrections, perturbative renormalizations, electroweak theory (2/3 from the US), quantum chromodynamics (3/3), supersymmetry (10/20), many experimental insights in particle physics and cosmology, and many other things…
Just want to make some points about baryon number conservation in intersecting D-brane models. Yes, it survives as a global symmetry at low scale, however this does not guarantee that there is no chance for proton decay. In principle, this global symmetry can be violated by instanton effects. It’s necessary to check the spectrum for any possible operators which might mediate rapid proton decay. On the other hand, if your model is some type of GUT at the high scale which gets broken to the standard mdoel, then there may already be operators which may mediate proton decay.
Dear mark and cowherd,
Thanks for your comments about our work. Perhaps I can make some comments.
With regard to proton decay and baryon number violation, this comes back to the nature of intersecting brane models as has been mentioned above in the thread. As long as the SU(3) originates from a U(3) = SU(3) x U(1) brane stack, with the U(1) being anomalous as normally occurs in intersecting brane models, then U(1)_B survives as an exact perturbative global symmetry of the low energy theory. At the string scale it becomes a gauge theory (the gauge boson of the anomalous U(1) becomes massive at the string scale by the Green-Schwarz mechanism). Baryon number is then only broken non-perturbatively. The existence of such global U(1) symmetries is a generic feature of intersecting brane models and so proton stability is not I think a particularly hard model building requirement.
On the presence of large volumes. I’m not sure why you think it should be unrepresentative to generate the hierarchy through the volume rather than anywhere else. The existence of the (susy) hierarchy can be expressed in the requirement that the gravitino mass be small. This is
m_{3/2} = e^(K/2) W = (flux-part)/Volume
To get hierarchically small m_{3/2} dynamically, you need a dynamic mechanism either to make W very small or Volume very large. That is, there are only two ways to get the susy hierarchy, and one of them is through a large volume. The statistics/counting results suggest that the flux-part W is expected to be 1 in natural units. If you accept this counting measure, then any dynamical generation of the susy hierarchy has to come through the volume. The large-volume models give a dynamical method to get exponentially large volume, and thus the hierarchy.
With the alpha’ corrections, they are always present and need to be included in every model, not just ours. But the fact that the volume is stabilised at such large values controls the alpha’ expansion and in particular kills the higher alpha’ terms.
This is analogous to what happens at a Banks-Zaks fixed point: as long as you stabilise at weak coupling you can forget higher loop effects.
With gauge coupling unification, you can’t have eveything 🙂
Best wishes
Joe
Germany leaded physics has given us relativity and quantum theory. USA leaded physics has given us string theory. This is very sad and deserves some worthy reflections about. Is fund rising the right way to pursue fundamental research?
Andy
PW said: “If your “outline†really is the vision that motivates much of current research, you might want to do the field a favor by fleshing it out from a blog comment, so people could see exactly what it is you have in mind, and addressing the question of what needs to be done to make it a reality, and what the rate of forward motion towards that goal might be. You’ve got a blog, I hear…”
EXCELLENT SUGGESTION! I was vaguely aware of the existence of an argument of the kind JD outlined, but it was exceedingly interesting to see it articulated in that degree of detail. A still more detailed explanation would be *extremely* helpful and might even move this debate along!
I’m not impressed by those models either since I like canonical gauge coupling unification and I was always suspicious by their reliance on the alpha’ corrections to get it to work. However, the construction seems quite generic although it’s sort of funny that it works only for CYs with a negative Euler character.
mark
I’m aware of this class of models, but have always regarded as unrepresentative, models that use large volumes to bring down the fundamental scales hierarchically [Horava-Witten was about my limit in this regard]. The work of Conlon and Quevedo is interesting, but I’m not convinced that it is representative of where the bulk of the IIB constructions consistent with the world we inhabit will lie. This just emphasizes Mark Srednicki’s point that we need to get a better handle on the space of solutions before we can really pose these arguments correctly.
There is a whole class of models called large volume Type IIB compactifications studied by Conlon and Quevedo where the string scale is typically at some intermediate scale. Their construction is fairly robust but I’m not sure how they address the proton decay issue. I’m surprised Peter did not bring those up as he claims to know lots about string phenomenology.
134 – Peter Woit writes:
“Mark,
I don’t buy your argument about proton decay. I’ve given mine. We disagree. People can look at both and make up their minds, or decide there’s no way to tell. In any case, it’s far from the main issue here.”
What argument? As Mark has noted, for you to claim that an anthropic [hence consistent with the Goldhaber bound] landscape is disfavoured by the Super-Kamiokande data, you would need to argue that it is statistically probable that string landscape solutions dynamically generate an “intermediate” mass scale [between 10^{11} and a few times 10^[15} GeV], in addition to the underlying string scale and the standard model scale whose generation is the problem that has dominated particle physics for the last 25 years. You have so far provided NO plausible argument that a third mass scale is generic. If a third mass scale is generic, how about a fourth? a fifth? What according to you is the number of mass scales that is most generic in the landscape, after anthropic cuts?
And yes, it is the main issue here! You have flatly asserted, here and elsewhere, that the longevity of the proton means that the anthropic landscape “has flat out been falsified”; but you then avoid giving any physics argument for the generation of the mass scale of the proton decay operator that such an assertion would require.
Hi Clifford,
Now that the thread has calmed down, I hope, I wanted to mention what my understanding of zeta regularization is, as compared to energy cutoffs and other things.
First of all, I disagree, on a philosophical level, with the idea that a “theory of everything” can be “only an effective theory”. When you are in grad school in physics or math (and I spent 8 years so situated), the most certain way you can choose that will result in your not solving a problem is to assume that it is unsolvable. With respect to understanding the elementary particles in an ontological fashion rather than in only an effective fashion, I say the same principle applies. If you assume you are too stupid to understand the elementary particles then you are right.
The reason energy regularization is ugly is that it introduces a physical parameter, an energy, that one must add to the long list of arbitrary parameters you need to describe elementary particles. For the physicists, zeta regularization is preferable in that it doesn’t bring in an arbitrary paramater.
Or better, zeta regularization doesn’t bring in an arbitrary parameter if you are a physicist. If you are a mathematician, and you’ve read Hardy’s book on divergent series (as I have), then you know that zeta regularization is accomplished by making a small adjustment to the series.
Such a theory (i.e. one that assumes zeta regularization) is equivalent to a theory with no need for zeta regularization where the series are slightly modified by a small constant. That small constant a mathematician would include with the series is an arbitrary parameter just like an energy choice. Such a theory, from a mathematical point of view, needs to admit that when it is talking about zeta regularization, it is implicitly including an arbitrary parameter, one that theory does not address.
Far preferable, I think, is to work in a version of QFT that avoids infinities.
By the way, I have Zee and have read it.
Many many many solutions
It looks that the scenario Mark beautifully described (#128) reflects a real issue for string theory and perhaps any competing theory. A huge number of solutions may indeed raise a difficulty about how to verify that the whole approach is valid. Internal integrity of the whole theoretical structure is probably a good step towards accepting such a theory. (Probably we are still far from this point.)
There is the philosophical question which comes back in circles in this discussions:
Can there be science without falsifiable empirical predictions?
It is much too early to tell if we will have to deal with this question, and the strong desire for falsifiable prediction is certainly justified. But I think we do have to be prepared for a ‘yes’ answer. In any case, a theory being empirically unfalsifiable (either temporary or permanently), cannot be regarded as equivalent of it being wrong or of being of no content.
Woit’s book
It is absurd to suggest Woit’s book as a place for physicist to learn physics and it is not clear why Peter thinks that making absurd insulting claims will reflect well on him and his ideas. As for Peter’s book let me repeat that I found the part about physics a very good popular description of high energy physics especially for readers who are mathematically inclined. The part attacking string theory is not of academic level and is overall not convincing (but provide interesting food for thought). Most of this part is philosophical with many anecdotes and strong rhetoric. Chapter 12 is technical while still on a popular level. And again, a detailed popular-scientific response for Chapter 12 can be useful. If such a response exists please please let me know. (As I said, Aaron Bergman’s short response is very useful.)
Beside this, I do not think Woit’s book is a “poisoning” book. The book is of some influence and can be regarded as rather successful, but it looks Woit misunderstands the nature of his own success. The charm of Woit’s book is that he does not come from a position of an authority on any of the topics discussed there but from a position of a curious rather scholarly bystander. So it is a little strange to see Peter behaving now like an authority whether it is on “what is science” or on “string phenomenology” not to speak of “what is the appropriate font in weblog discussions.” (And regarding fonts the recent CAPITALIZATION (#130) was really really confusing.)
We do witness a certain shift of rhetoric in popular descriptions of ST between something like “string theory is on the verge of success and superstrings and M theory are two towers that are solid permanent parts of our understanding of nature” to “string theory represents one of the most daring, difficult and deep human scientific endeavors. It is not clear how far we are from success and success is not guaranteed”. Both these views and a whole spectrum of variations reflect some string theorists’ opinion all along. It is only natural that in the past people who were more optimistic were also more interested in the popular and “outreach” activities. At present (like on this post), we see a certain shift in rhetorics regarding string theory towards the second description. This reflects primarily the scientific emerging story and the findings within string theory, but perhaps the books of Woit and Smolin and the public debate also contributed to or triggered this.
For the general public, both these descriptions can be equally appealing. For young Ph.d’s I find the second description even more appealing than the first. This shift in popular rhetoric does not matter at all for how string theory is practiced, and has very small relevance if any to issues of funding and to the stature of string theorists in the scientific community.
Woit’s book and blog also attract some “anti science” voices and sentiments (and we certainly see many anti science-establishment and anti successful-scientists remarks.) I do not think anybody can take for granted not only string theory but the scientific endeavor as a whole, and making sincere effort to explain from time what science is all about is worth the trouble. (But frankly, neither the scientific endeavor nor prominent parts of it like string theory are in any immanent grave danger.)
The weblog discussion
The phenomenon of weblog discussions on academic and scientific matters is quite fascinating. It is very moving to see shoulder to shoulder, discussing scientific issues, for example, Chris Oakley, Joe Polchinski, Mark Srednicki, and Toni Smith (named ordered alphabetically), and it gives a good name to the scientific spirit and scientific community.
A lot of the discussions are repetitious (maybe the weblog ethic should exclude repeating the same idea the same way more than three times a month; with an exception for Peter – 30 times). But some parts are very interesting. Some personal reflections of Polchinski and Srednicki (and others) on their own career and on early history of string theory look valuable.
I really liked the long discussion (on cosmic variance) initiated by Oakley on QFT, renormalization and mathematics (“ST and public debate” late 400’s).
I also found the discussion of Gauss-law and higher representations of gauge groups (same thread late 300’s) of interest. There were several interesting explanations (with deep connections between them) why higher representations cannot appear in any variation of QED (and more general theories). The starting point for this particular exchange was an idea of Peter Woit that he himself quickly explained was not meant to apply to QED.
At the end, I still was not convinced that high order representations whose combined effect on Gauss law will be zero cannot eventually emerge in a variant of QED. (If only to show (in a friendly way) that Peter with all this debate and crusade mode will not be able to recognize a promising idea worth working on; even if it is his own idea. 🙂 )
Peter, it’s fine if you don’t buy my argument about proton decay. As I have said repeatedly, it’s really just a guess. But by the same standard, you cannot claim that the landscape has made a prediction that has been falsified, when that “prediction” consists solely of your guess as to how things will work out.
And what did I say that constitutes an “ad hominen argument”? That I dared to point out that your crtiicism, such as it is, applies not just to string theory, but to every research program in particle theory, including your own?
I agree completely that “people should be honestly evaluating what has worked and what hasn’t, and trying to figure out how to encourage people to do the kind of work necessary to come up with new ideas”. I think that’s exactly what’s happening, as it always does. The difference is, I believe the most promising avenues are still within string theory. Jacques has outlined one way things might work out well. You disagree, and want to pursue something else. I think that’s fine. I even think research of that sort deserves funding.
What I strongly disagree with is using an argument that actually applies to all current research to denigrate only one particular area of research.
Good. Then you’ll retract the rest of the statements which follow from your
assertion?
It is, as I said, a fairly well-known point of view. I recall first discussing it with Shamit Kachru, shortly after KKLT came out. And it’s clear that this sort of picture motivated not only much of his work over several subsequent years, but that it has motivated the investigations of many other people as well (see, for instance, this post on my blog).
Perhaps I should spend more time writing over there, and less time engaged in pointless arguments with you.
Mark,
I don’t buy your argument about proton decay. I’ve given mine. We disagree. People can look at both and make up their minds, or decide there’s no way to tell. In any case, it’s far from the main issue here.
You continue to evade the very simple question I keep posing to you, now deciding that the way to answer it is ad hominem argument. I draw the conclusion that you have no idea at all how the landscape is supposed to lead to a scientific prediction, but think it is a good idea to defend research into it and attack those who criticize it, for rather unscientific reasons.
Yes, nobody has a good, promising idea about how to make progress on unification. I’m not ignoring that, but say it repeatedly, in the book and many other places. Seems to me that in such a situation people should be honestly evaluating what has worked and what hasn’t, and trying to figure out how to encourage people to do the kind of work necessary to come up with new ideas. Defending the indefensible (the landscape) is just digging the field deeper and deeper into the rut it has gotten into.
Jacques,
My apologies, your “outline” qualifies as “logically possible” also I suppose. It is, however, based on layers of wishful thinking about what you can reliably calculate and its possible agreement with the real world that are much more numerous than the statistical proposals to predict some gross feature (e.g. low or high scale supersymmetry breaking) of the universe based on plausible assumptions about the structure and measure on the landscape.
If your “outline” really is the vision that motivates much of current research, you might want to do the field a favor by fleshing it out from a blog comment, so people could see exactly what it is you have in mind, and addressing the question of what needs to be done to make it a reality, and what the rate of forward motion towards that goal might be. You’ve got a blog, I hear…
Where is the “good evidence” that the landscape makes incorrect predictions about the proton lifetime? You made this claim in comment #53, claimed you didn’t make it in comment in #115 (see my comment #121), and have now made it again in comment #130. You have repeatedly refused to present this “good evidence”, ignored all scientific arguments to the contrary, and most importantly ignored the fact that all such arguments are, at this stage, really just guesses as to how the proton lifetime might be distributed over landscape vacua that are otherwise consistent with the Standard Model. Yet you somehow believe that your guesses have a privieged status, and that an effective rebuttal to a scientific argument consists soley of “I don’t buy it.”
And where are the falsifiable predictions of other research programs? Your own research on representation theory, last reported in hep-th/0206135, led to results whose connection with the Standard Model was “exceedingly speculative and very far from what one needs to construct a consistent theory”, and furthermore did not include gravity at all, even speculatively. Is anyone else doing any better in (1) producing something consistent with all known facts about the Standard Model plus gravity, and that (2) makes a falsifiable prediction?
The truth is that all research programs currently suffer from the same stipulated failure as string theory, because it’s just not very easy to produce the Standard Model plus gravity from any starting point. Your criticisms of string theory ignore the fact that to the extent that they are valid at all, they apply to all current research on particle thoery by everyone, including you.
This is untrue, even with your “I HAVE SEEN” caveat thrown in. Could you explain why the proposal I outlined to you (which, I should add, motivates much of the work in the subject) is not “LOGICALLY POSSIBLE.”
Mark,
I don’t know how many times I have to keep trying to explain this to you:
1. I DON’T BELIEVE THE LANDSCAPE MAKES ANY LEGITIMATE SCIENTIFIC PREDICTIONS AT ALL. NEVER HAVE SEEN ONE, DON’T BELIEVE THERE ARE ANY. THIS IS WHY I OBJECT TO IT AND DESCRIBE IT AS PSEUDO-SCIENCE.
2. THE ONLY LOGICALLY POSSIBLE PROPOSALS I HAVE SEEN FOR LANDSCAPE PREDICTIONS ARE STATISTICAL ONES. I PERSONALLY DON’T BELIEVE THESE MAKE SENSE (YOU CAN NEVER KNOW THE MEASURE). IF YOU DO (UNLIKE ME) BELIEVE THEY MAKE SENSE, THEN YOU HAVE THE PROBLEM THAT THERE IS GOOD EVIDENCE THAT, WITH GENERIC ASSUMPTIONS ABOUT THE MEASURE, THEY MAKE PREDICTIONS (INCLUDING THAT OF THE PROTON LIFETIME) THAT ARE WRONG.
Got it?
As for your next comment, you’re again just completely ignoring what I’ve written in response to this argument from you about a dozen times, here it is again:
I HAVE NO IDEA WHETHER THERE IS A UNIQUE THEORY OR NOT, OR WHAT THINGS ARE ENVIRONMENTAL AND WHAT ARE PREDICTABLE FROM FIRST PRINCIPLES. BUT I DO KNOW THAT IF YOU WANT TO DO SCIENCE YOU HAVE TO MAKE FALSIFIABLE PREDICTIONS. THE PROBLEM WITH THE LANDSCAPE IS THAT IT DOESN’T.
Again, you keep ignoring the question I ask you over and over: if you think the landscape is science, exactly what kind of falsifiable prediction do you expect to get out of it, and give a solid reason for why this may work out.
Re: #91 #98 and #112 by Mark Srednicki
Mark
Exactly!
To sharpen the formulation of this, lets consider the dimension 6 proton
decay operators which are the leading dimension one can form with only
standard model fields. As you know the suppression of the proton decay
rate is encoded by inverse powers of the mass scale M [typically it’s
g^{4}/M^{4} in the decay rate for D=6 operators, with g a unification
scale gauge coupling]. With standard RGE extrapolated gauge couplings, the
lower bound on the scale of M to satisfy the Super-Kamiokande bounds on
the proton lifetime is of order a few times 10^{15} GeV [ie. below string
unification scales]. But already to satisfy the anthropically required
Goldhaber bound [using Woit’s number of 10^{17} years to avoid possible
objections] on the lifetime of the proton translates into a lower bound on M
of a few times 10^{11} GeV. Woit complains above that one is assuming a desert in
the analysis of proton decay, but this is already imposed by the anthropic
requirement of our continued survival in the face of proton induced
radioactivity. Now, to have proton decay at a rate consistent with the
Goldhaber bound [which we certainly need to impose as an anthropic
selection criterion on the string landscape], but ruled out by the
Super-Kamiokande measurement [which is what Woit would require to be able
to claim that there was an anthropic landscape prediction that was ruled
out by Super-K], we would need string solutions which not only stabilized
the electroweak scale [hierarchically] below the string scale, but
which also stabilize a second “intermediate” scale hierarchically above
the electroweak scale, but below the string scale, as you noted above.
Given how hard it is to construct models with large mass-scale separations
which are stable against quantum mechanical corrections, it seems to me
very unlikely that models with three hierarchically separated scales
should predominate numerically over models [or solutions] with two
separated scales in the a priori statistics of the distribution of solutions
in the string landscape [imagine that the opposite were true; would models
with four separated scales be expected to predominate numerically over models
with three separate scales? and then what about induction on this
argument…?]. So all my experience tells me that it’s likely that string
solutions that already survive the anthropic cut of the Goldhaber bound
on proton decay, will predominantly give predictions consistent with the
Super-Kamiokande limits. ie. Based on these physics arguments my expectations
are the opposite of Woit’s alleged prediction.
But then again, this issue can’t really be decided until we know the
a priori statistical distribution of string vacua in the landscape, which is
the point that you’ve already made several times in posts above…
There is an interesting fundamental question here that goes beyond the current string paradigm. It is this: will the ultimate “theory of everything” have one and only one solution, a solution that looks like our universe? Or, will it have many, only one of which looks like our universe?
The great hope has always been that the answer will be “one and only one”. This was the hope for the physics of hadrons in the sixties, when it was widely speculated that fundamental principles (the analyticity, unitarity, and crossing symmetry of the S-matrix) would uniquely determine all properties of all hadrons.
That hope failed. We now know that hadronic physics is described by a particular quantum field theory, quantum chromodynamics, based on a particular gauge group, SU(3), with a particular set of matter fields (quarks), with a particular pattern of masses. There is nothing unique about it.
Despite Jacques’ correct observation that it was always obvious that string theory would have many solutions, there was a hope that there would be some “vacuum selection principle” that would somehow pick out one of these solutions as uniquely favored, and that this solution would match our universe.
This hope has now faded in light of new results, just as the hope for hadronic physics faded in the early seventies.
Peter Woit and others don’t want to give up this general hope. They want to abandon the most promising framework we have (the only known framework that accommodates both quantum field theory and gravity in a natural way), and strike out in search of the next “analyticity, unitarity, and crossing!”, the next set of general principles that will uniquely determine the Standard Model.
That’s fine with me (though I think the chances of success are essentially zero). But Peter also insists that everyone else should do this too.
Is revisiting a failed ideology of the sixties a good plan? Time will tell.
Peter Woit wrote:
I quoted the whole paragraph where you made your assertion that the landscape had made a “prediction that has been flat out falsified”. I then quoted the sentence where you claimed never to have said any such thing.
Since you have now apparently repudiated your statement that the landscape predicts a too-short proton lifetime, I assume you will not be making that assertion again.
I already answered this. Try reading what I wrote.
The Banks-Dine-Gorbatov argument is that the Anthropic Principle alone cannot explain the values of the SM parameters that we see. There must be some other mechanism(s) in operation.
On this, everyone (except, perhaps, for you) is in agreement.
And, indeed, Susskind pointed out one such mechanism and others in this thread have pointed out others, which explain why the proton lifetime cannot vary arbitrarily on the landscape and is, instead, constrained by other factors.
Jacques,
As usual you delete the relevant part of what I write before quoting it and responding. Again, all I’m asking for is a specific example of the sort of thing you think it may be possible to predict using the landscape. Which of the numbers that characterize the SM do you believe it may be possible to predict (or what pattern amidst those numbers?) What prediction of any kind about BSM physics effects visible at the next generation of accelerators might the landscape make possible?
mark (lower case..)
By now there’s nearly a 25 year history of a large number of claims very similar to the ones you discuss about supposed progress of this kind, none of which has ever come anywhere close to making a real prediction. I just don’t see at all how these latest two examples are any different.
Mark (upper case..)
Like Jacques you just delete relevant parts of what I write when that’s the only way you can make an argument. The part you quoted referred to what I “believe”, the part you deleted explained exactly what I do believe: claims of statistical predictions of any kind from the landscape don’t work.
Besides just deleting what I write, you also simply ignore any of it that you find inconvenient. You continue to ignore my question: if you want to disagree with my claim that the landscape is unpredictive, give me an example of something it can possibly predict.
You ignore not only this, but also issues about the proton lifetime: what about the Banks, Dine, Gorbatov argument? Do you have an argument against it? Susskind’s argument is that maybe there is no low-energy supersymmetry. If you believe this, the implication is that the Landscape does make a prediction: no low-energy supersymmetry. Why has this prediction not been widely publicized? Could it be because it direcly contradicts the idea that “string theory predicts low-energy supersymmetry” and we can test this at the LHC. Could it be because it just makes it more obvious that any Landscape “prediction” is a joke?
As for your argument that proton decay will be suppressed in the landscape by a large enough factor because it is “hard” to get any intermediate energy scales between the Planck and electroweak scale, I just don’t buy it. There are all sorts of baryon-number violating effects at all sorts of energy scales that generically could be there. What you are claiming is essentially a new prediction of the landscape: that it predicts and explains the desert hypothesis. I’ve looked carefully for claims of landscape “predictions”, and never seen that one before. I don’t buy it.
Mark Srednicki (122) said that I (120) was “… missing a key point:
John Schwarz was hoping his model was the unique finite and realistic model,
not the unique finite model. …”.
It seems to me that search for a “unique finite and realistic model” is what physicists should do, and I agree with Schwarz in searching for that,
because
search for “the unique finite model” without the “realistic” would leave string theory vulnerable to being, as physics, “Not Even Wrong”,
so
I think that “realistic” should be implicitly included in the criteria for any efforts to construct/find string theory physics models.
Tony Smith
Well, Peter, I guess claiming you never said it should count as a retraction. Sort of.
Tony, you are missing a key point: John Schwarz was hoping his model was the uniques finite and realistic model, not the unique finite model. As the abstract you quote notes, he had a whole list of one- and two-loop finite models, but he thought that only one had a chance to be realistic. And, even this list was already restricted to chiral models.
Peter Woit wrote (in comment #53 above):
Peter Woit wrote (in comment #115 above):
This is a historical point (relatively minor to discussion about actual finding or construction of a string theory model that, as Jacques Distler said (117), “… bears more than a passing resemblance to the Standard Model …”),
but
Jacques Distler also said (108) “… For the very start (1984-85) … No one ever thought that SU(3)xSU(2)xU(1) with 3 generations would emerge as the unique solution to string theory …”.
Since SU(5) GUT includes SU(3)xSU(2)xU(1), it is clear that in 1984-85 John Schwarz did in fact think that such a model “… would emerge as the unique solution to string theory …”.
At the 1984 APS DPF Santa Fe meeting, John Schwarz gave a talk
(on work with Shahram Hamidi) entitled
“A Unique Unified Theory That Could Be Finite And Realisticâ€,
in which he discussed “SO(32) and E8xE8 superstrings†with respect to finding “the correct low-energy (compared to the Planck mass) theory in four dimensions with which to make contactâ€.
Swarz went on to say that “In collaboration with J. Patera, we have classified all the chiral N=1 theories that satisfy the one-loop (and hence two-loop) finiteness conditions. The list includes theories based on E6, SO(10), SU(5), and SU(6) that can describe three or more families without mirror partners.
However, if we also require the occurrence of elementary Higgs fields in representations that can give realistic symmetry-breaking patterns, then one unique scheme is singled out. …
The unique model that is potentially finite and realistic is based on the gauge group SU(5).
… The three-loop calculation could result in a dramatic failure and is therefore of utmost importance. …â€.
After Schwarz made his 1984 Santa Fe talk, a lot of work was done on that SU(5) structure. For example,in Physics Letters B, Volume 160, Issues 4-5 , 10 October 1985, Pages 267-270, D. R. T. Jones and A. J. Parkes wrote a paper entitled
“Search for a three-loop-finite chiral theoryâ€. Its abstract stated:
“Grand-unified theories have been constructed out of supersymmetric SU5 theories which are finite at one and two loops. We investigate the three-loop divergences in these models and find that they can never be three-loop finite …â€
Despite Schwarz’s declaration that his 1984 superstring theory was predictive and testable,
he did not admit defeat upon its failure to pass the three-loop test.
How history may evaluate his stubborn pursuit of string theory in the face of its initial failure may depend on whether or not the string theory community ever finds/accepts a string theory model “… that bears more than a passing resemblance to the Standard Model ..”.
Tony Smith
“Nobody knows whether string theory is right or wrong because it is very much a work in progress.”
Would it be correct to predict that the some major insights and tools gained by string theory to physics and to its mathematical infrastructure may well stand regardless of the question “whether string theory is right or wrong” which looks by itself well beyond the horizon?
Peter:”I see zero evidence that the papers you mention will lead to falsifiable predictions”
I agree that these particular papers have not resulted in “falsifiable predictions” yet. This is called work in progress Peter. However, the fact that the model found by Ovrut and Co. automatically gives one SM generation very light is a generic prediction of their model. By the way, the CY manifold they found has very few moduli, contrary to your claim that realistic compactifications are “ugly and complicated”. To counter your favorite argument that one can construct lots and lots of similar models I pointed you to the second paper where it was shown that three-generation models like the one in the first reference are extremely rare and this whole discussion of lanscape statistics seems completely irrelevant.
Since no one has yet found a string theory vacuum that bears more than a passing resemblance to the Standard Model, I’m not sure what for you would like that prediction to take. I did explain how models, like the ones which have been considered heretofore, would to lead to predictions. But, without even one such vacuum in hand, I can’t tell you the detailed form those predictions will take.
Believe me, if I knew, you would be the last person I would tell.
You, on the other hand, have not given a shred of a rebutal to my argument (except to repeatedly assert that the landscape is inherently unpredictive, as if mere repetition were a substitute for a logical argument).
Jacques,
I followed that link, but it provided no specifics, just some abstract hand-waving: Give me explicitly a falsifiable prediction of the sort that you think the landscape can provide, together with a plausibility argument that it will be possible to do the kind of calculation necessary to make this prediction reliably enough for it to be a falsifiable one.
Mark,
Sorry, but I just don’t believe your flat-out assertion that the difficulty of generating any kind of intermediate scale between the electroweak breaking scale and the Planck scale solves the problem of why the proton lifetime is 10^15 times longer than the anthropically expected value.
No, I never claimed that I believe that the landscape has made a real prediction that has been flat out falsified. I believe the landscape actually makes no real predictions, about proton decay or anything else : it is pseudoscience and an excuse to cover up failure. This is the point at issue, which you keep ignoring and trying to hide from. Again, give me a plausible scenario in which the landscape makes a standard, falsifiable prediction about particle physics.
I don’t understand why the Landscape needs to make predictions to be falsified: surely a computation of particle masses (in the contrasting aforementioned approach) is sufficient.
I explained (in some detail) in what form I expect that predictions will emerge from the Landscape. If you can’t follow the hyperlink, there’s not much that I can do to help you.
Peter, once again, you have no basis other than pure assertion to say that the distribution of proton lifetimes is flat.
In the simplest compactifications, everything is either massless or has a string- or copactification-scale mass. Getting any scale that is well below these scales is the hard part. Given that it’s tricky to generate low-energy scales, I know of no reason whatsoever to expect a flat distribution of particle masses below the string scale and above the electroweak scale.
If you do, please say what it is.
If you don’t, please retract your claim that the landscape has made a prediction that “has been flat out falsified”.
mark,
I see zero evidence that the papers you mention will lead to falsifiable predictions.
Jacques,
All you are doing is evading dealing with the arguments I was making, and joining Clifford in his childish games.
You claim that no one ever believed that string theory would predict the the gauge groups and number of generations of the SM. That’s not the way I remember it, but fine. Well, if not those, then
1. What did they expect to be able to predict back in 1985? Fermion representations? gauge coupling constant ratios? Fermion mass matrices? Supersymmetry breaking?
2. Now, more than 20 years later, what do string theorists believe they can predict?
The landscape is nothing more than an elaborate excuse for not being able to make testable predictions about particle physics. If you want to argue otherwise, let’s hear what testable predictions it is supposed to produce, and by what means.
…including the `three-generation’ manifolds with \chi=-6 …
Hmm. Chi = -6 for the moduli of the six punctured sphere, which is the way to count generations in the twistor triality setting related to the model that Tony Smith has suggested. So I’m wondering: why do we need the landscape?
Peter, why are you so hung up on this landscape statistics stuff? This is not what the vast majority of “string phenomenologists” are doing. People are building realistic models and trying to compute things, for example:
Yukawa Couplings in Heterotic Standard Models
Braun, He and Ovrut
Abstract: In this paper, we present a formalism for computing the Yukawa couplings in heterotic standard models. This is accomplished by calculating the relevant triple products of cohomology groups, leading to terms proportional to Q*H*u, Q*Hbar*d, L*H*nu and L*Hbar*e in the low energy superpotential. These interactions are subject to two very restrictive selection rules arising from the geometry of the Calabi-Yau manifold. We apply our formalism to the “minimal” heterotic standard model whose observable sector matter spectrum is exactly that of the MSSM. The non-vanishing Yukawa interactions are explicitly computed in this context. These interactions exhibit a texture rendering one out of the three quark/lepton families naturally light.
There are still plenty of technical issues to overcome but they are indeed, techical like for instance, how to compute the Kahler potential for the visible sector matter fields for Heterotic compactifications on a Calabi-Yau. It is a complicated problem but it’s a techical one. I wish more people doing formal string theory would spend more time one these “realistic” problems.
By the way, Peter, have you seen this paper:
Triadophilia: A Special Corner in the Landscape
Candelas, de la Ossa, He and Szendroi
Abstract: It is well known that there are a great many apparently consistent vacua of string theory. We draw attention to the fact that there appear to be very few Calabi–Yau manifolds with the Hodge numbers h^{11} and h^{21} both small. Of these, the case (h^{11}, h^{21})=(3,3) corresponds to a manifold on which a three generation heterotic model has recently been constructed. We point out also that there is a very close relation between this manifold and several familiar manifolds including the `three-generation’ manifolds with \chi=-6 that were found by Tian and Yau, and by Schimmrigk, during early investigations. It is an intriguing possibility that we may live in a naturally defined corner of the landscape. The location of these three generation models with respect to a corner of the landscape is so striking that we are led to consider the possibility of transitions between heterotic vacua. The possibility of these transitions, that we here refer to as transgressions, is an old idea that goes back to Witten. Here we apply this idea to connect three generation vacua on different Calabi-Yau manifolds.
After reading this abstract do you still care about the 10^500 vacua? I certainly don’t!
No. I suggest you reread what I wrote.
Complete nonsense. For the very start (1984-85), it was clear that you could get a variety of low-energy gauge groups and numbers of generations. No one ever thought that SU(3)xSU(2)xU(1) with 3 generations would emerge as the unique solution to string theory. That’s not the sort of prediction people expected to emerge then, and so it’s a pretty flimsy straw man to erect as an example of the failures of string theory in the interim. (Even you can do better than that.)
Which is why you should probably work on something else.
If you’re willing to include vacua that look nothing like the Standard Model in your ensemble, then — in most of them — there isn’t even such a thing as a “proton.” So I’m not sure what you are purporting to be calculating.
In any case, the existence of a landscape of vacua that look nothing like the real world is not a feature peculiar to string theory. It is a property of any theory containing the Standard Model (with neutrino masses) coupled to gravity.
That “ideology” is, again, a straw man. See the arguments of Dine et al.
I gave exactly such an argument, and linked to it above.
I may disagree with Mark about various things. But about your complete failure to give an argument backing up your claims, we are in complete agreement.
Clifford,
I’m answering the questions put in front of me. People who actually know something about the topic can decide what they think about my answers. You can’t because you don’t actually understand the issues being discussed.
Your behavior is really amazing. To think that for the longest time I couldn’t figure out why you wouldn’t engage in any discussion of the science at issue here, just instead repeating childish taunts. The answer was obvious: you don’t understand any of this. Silly me.
Now I really suggest you read my book. You would learn a huge amount about physics from it…
Mark,
Maybe you should argue this one with Jacques, who seems to want to argue certain issues with me, but not that one.
I’m claiming very specifically this: of the classes of string backgrounds I’ve seen discussed, take many random generic choices of the data which specify the background leading to a large statistical sample of possible gauge groups, fermion representations, symmetry breaking scales etc. Look at those choices in which you can embed the standard model particles. Look at the statistical distribution of proton lifetimes. I don’t see anything in the structure of this problem that would put the bulk of the probability at 10^15 or whatever it is times the anthropic value you would expect if the probability were more or less flat.
All you and others have answered in response to this argument is to point to, not generic string theory backgrounds, but ones specifically constructed to not disagree with experiment, in particular by pushing baryon number violation up to the GUT scale.
Look, I’m repeatedly making a simple claim here: there is no plausible way to get a prediction out of the landscape that doesn’t violate what we know about physics. If you want to show that I’m wrong, go ahead and explain to me such a plausible possibility of how someday someone is going to get a falsifiable prediction out of the landscape. Let’s hear it. If you can’t produce it, why is this a reasonable research program?
Peter…. Just back up what you claim with a scientific argument. Stop trying to avoid that simple request.
Answer the questions put in front of you. Don’t try to hide.
Go for it.
Cheers,
-cvj
The last two pages of Aaron Bergman review of Peter’s book contain a nice discussion of the (popular) scientific claims by Peter mainly from Chapter 12.
http://zippy.ph.utexas.edu/~abergman/Review.pdf
(I also found Bergman’s recent post “What is string theory” very impressive.)
Peter, you claim that you “argued that there is no reason at all to believe that a stable proton is statistically likely over the whole landscape, quite the opposite.”
In fact, you have made no such argument; you have merely made an assertion that this is the case, with nothing whatsoever to back it up.
Clifford,
OK, you agree that you don’t know what you’re talking about when it comes to string phenomenology, just like you don’t know what you’re talking about when it comes to my book and Lee’s. Thanks. I’ll let people who actually know something about both subjects judge for themselves whether my arguments at various levels and in various places make sense. You don’t have a clue about this, and yet are completely comfortable attacking me. Remarkable.
Mark (and Jacques)
My comment that the landscape is a “logical possibility” was paired with the argument that it is not science since you can’t get any scientific predictions out of it. That’s what this whole argument is about: do the people promoting investigation of the landscape have a plausible argument for how they’re ever going to get a real prediction out of it? If they do, they’re doing science, if they don’t, they’re not.
To discuss this I think you have to look honestly and carefully at a very complex subject, that of what people have learned during the more than 20 years of effort to study possible “string backgrounds”. I’m well aware that it’s not enough to just invoke the fact that there are an absurdly large number of these, but you also can’t just ignore the fundamental problems that have turned up and keep repeating “it’s too early to tell”.
As Jacques sometimes points out, it’s true that it’s incredibly difficult to get anything that looks even roughly like the SM out of string backgrounds. All people have managed is to come up with more and more complex constructions, getting only the gross features of the SM out (e.g. the gauge groups, representations, number of generations). Personally I don’t think it is possible to look at this history and come to any other conclusion than that this is a failed project, failed in exactly the way wrong ideas often fail, by having to add more and more complexity and wishful thinking to them until they collapse of their own weight, never having come close to having made a testable prediction.
Until a few years ago, the standard argument you heard from string theorists justifying research into string unification was that they hoped that a better understanding of non-perturbative string theory would lead to finding a way to get a tractable set of ground states that included the SM, and would be predictive about most features of the SM and about beyond SM physics. I thought this involved way too much wishful thinking and argued this in many places. Many string theorists I talk to still tell me that this is essentially what they still think. Some hope for purely 4-d strings that will thus avoid the problems introduced by extra dimensions, some have other hopes.
In recent years, some string theorists started arguing that there is no hope of this working out, that, whatever non-perturbative string theory is, the Landscape has to be there, with its huge complexity of possible solutions. I’m far from the only one who believes that the existence of the Landscape is incompatible with predictivity, see Steinhardt’s recent comments on edge.org, or talk to any number of string theorists and other particle theorists. My argument here was about a specific claim for how to get predictions out of the Landscape: by looking at the whole thing, and trying to make a statistical argument that we should be in parts of the Landscape that are statistically likely. I argued that there is no reason at all to believe that a stable proton is statistically likely over the whole landscape, quite the opposite.
Jacques wants to ignore this, I guess acknowledging that this kind of prediction can’t work. If so, no point in technical arguments about intermediate energy scales and warping, since we agree. As far as I can tell, he wants to largely just stick to the problem of constructing string backgrounds that look like the SM. As far as most of the things string theory was originally supposed to explain, things like the gauge group, particle representations, number of generations, he has simply given up. There are supposedly consistent backgrounds with the SM values of these, and with all sorts of other values. The Landscape ideology says that you just can’t explain these things, they’re environmental. The question remains whether he has a plausible argument for ever being able to explain anything. What is it that you can ever hope to either calculate exactly, or produce a peaked statistical distribution for, peaked at the correct experimental value? I have yet to see any plausible argument for evidence for such a thing, just more and more complicated constructions, patched together to avoid contradiction with experiment. No, I don’t have a “proof” that no such thing can be found, but I don’t think the kind of standard minimal evidence required to justify a scientific research program exists here. There’s nothing here but a refusal to face up to failure.
Peter, this is another laughable attempt to distract from your being unable to back up your strong claims. Please either back them up, or admit that you cannot.
I am freely able to declare that I am not an expert in all areas of string theory, and have written no papers on string phenomenology. I’ve had some discussion on blogs about some general aspects, but I won’t point to them since I will not be so self-deluded as to believe that they are rigourous scientific arguments. They constitute my own gut feelings about ongoing research. However, after almost 20 years of work in this area, I can tell a scientific computation from a vague set of assertions in any area of this highly inter-connected field.
But really, a botanist can tell that your scientific arguments are not anything like up to the strength of what you’re claiming about all of our research, so you’re hiding again.
Let’s be clear:
You are the one publicly and loudly trying to deceive everyone into thinking that you know the outcome of all our research. I am making no such claims about anyone’s research. (I would not be so presumptuous, frankly.) Therefore it is you who needs to demonstrate your detailed knowledge of string phenomenology, not me. You’re failing miserably right now (as you have before), in this very thread, in the act of arguing with people who are experts in the areas you’ve focused on, and in even answering soft questions about your claims from non-expert commenters.
Cheers,
-cvj
Clifford,
As far as I know, it’s just a fact that you have never, not once, engaged publicly in any sort of discussion of the scientific issues under discussion here having to do with the problems of getting the Standard Model or any sort of prediction out of so-called “string backgrounds” designed to produce a unified theory. If I’m wrong about this, please point me to where you have done so. I don’t doubt that you’re quite a bit more knowledgeable than me about some aspects of string theory, but as far as I can tell, you know hardly anything about the field now known as “string phenomenology” and why no one has been able to get predictions out of it. You cover up this ignorance by repeating endlessly “no one knows, it’s too soon to tell”. Despite this lack of knowledge, whenever I try and engage in serious discussion of the subject, you take the opportunity to insult me as incompetent. Truly remarkable behavior.
Peter, earlier you agreed that the landscape is a logical possibility. In exploring that possibility, of course we want to restrict attention to those portions that look like the Standard Model.
You have no scientific argument that intermediate scales are common in the landscape, whether or not we restict to Standard-Model like vacua. It is just your guess.
Your guesses do not constitute a “falsification” of the landscape.
Why do you think that’s the relevant question?
Or, to put things differently, what question do you think you are trying to answer?
The question I’m interested in is: what (if anything) can string theory predict about the Standard Model parameters (more generally, about particle physics at accessible energies).
I have no interest in vacua on the landscape that look nothing like the real world.
Indeed, if you are willing to contemplate those, and include them in your vaguely-defined statistical computations, I see no reason why you shouldn’t consider the statistics of the landscape of vacua of the Standard Model itself.
Intermediate scales are hard to generate. This has been a longstanding impediment to understanding many features of physics between the Planck scale and the electroweak scale.
Nowadays, we know there are interesting mechanisms for generating intermediate scales (e.g. warping). Finding baryon-number violation suppressed by some intermediate scale is another matter.
I would like to hear your explanation for how you think that arises in actual string compactifications. Vague handwaving, “you can get just about anything you want,†just doesn’t cut it for me.
Peter,
I think that it’s great that there’s some sort of physics discussion going on. The point of the part of the discussion that I’ve been involved with is trying to get you to back up your claims that you already know the outcome of the string theory research program. Nothing you’ve said so far has come close to backing up such claims, as is clear from everything you’ve said – as has been pointed out by many others here. What is going on instead is a standard (albeit not uninteresting in part) ding-dong argument of the “this is what I hope for” vs “no, this is what I hope for” type that we’ve seen for several years on these blogs. I definitely don’t have anything new to say in that department. It is the research, and compelling scientific argument (which you’ve not been demonstrating), that will push our knowledge forward, not a battle of hopes and expectations. My purpose here is not to engage in a childish exercise of showing whether I know more string theory than you. That’s just silly, for several obvious reasons.
Instead, I’ll just keep pointing out to those who’ve kept an open mind that you keep coming up short in demonstrating your claims.
Cheers,
-cvj
Mark,
You’re again posing the question by ignoring almost all of the landscape, and just restricting attention to that part of it that looks like the SM, with experimentally inconvenient non-SM effects pushed to much higher energy scales. That landscape statistics should be concentrated there is pure wishful thinking, to which you are just adding another layer of wishful thinking by saying you think maybe intermediate scales are hard to generate.
Clifford,
I can’t help noticing that you don’t in any way respond to any of the points being made on either side in the serious discussion going on here between me and some other people, but do think it’s worth your time to engage in discussion with Gina, who has no idea what she’s talking about. People might get the idea that, this is because, like her, you have no idea what you are talking about.
piscator,
Like others here, you’re pointing out that if one looks just at backgrounds constructed to give something close to the SM, you get baryon number conservation because that’s a property of the SM. But, just ignoring the rest of the landscape except the parts that look like the SM is not what the anthropic landscape program says to do. I doubt there’s any way to sensibly do statistics on the landscape, which would involve knowing how to do relative counts of the kind of backgrounds you discuss and backgrounds that involve a GUT group. But the only proposal from the anthropic landscape people about how to get predictions involves doing this. I’d argue that, if you can do this, generically on the string landscape you’re not going to just get the SM, but will get the SM out of breaking of larger groups, and thus generically won’t have baryon number conservation. This is what happens in the conventional heterotic models.
But sure, you can always claim that “maybe probability is concentrated on the SM-like models”. I just don’t see a reason for that other than wishful thinking. It is exactly this that makes the whole business a pseudo-science. You can argue away any inconvenient prediction. And I don’t see any way this situation is going to change, no matter how many people work how many years on studying string backgrounds.
As for the anonymity business, perhaps my comment was too strong. I’ve had to put up with quite a lot in the way of personal attacks conducted under the cover of anonymity, and have been surprised to find some of this coming from supposedly reputable physicists, so this colors my views. I still think the only good reason for anonymity is that this has become a highly contentious debate, and especially untenured people may reasonably want to try and avoid getting caught in the cross-fire. Professional academics have traditionally not carried on discussions about their subject anonymously, but done so openly, taking responsibility for what they say. In the only examples I know of where anonymity is traditionally used, in things like referee reports, those responsible for adjudicating the argument know who is doing the arguing. The problem with arguing anonymously is just that of not having to take any responsibility for the quality of ones arguments.
Gina,
You (and Anonymous Hero) have highlighted the point I’ve been trying to make in the thousands of words with:
In short:
[tex]\,\, \mbox{\rm popular scientific argument}\,\,\neq \,\,\mbox{\rm scientific argument}[/tex]
Gina,
Most people don’t presume the outcome of and condemn out of hand the entire output of a field of research by thousands of people with “a popular scientific argument”. To do this, one should use the language and tools of the field concerned to make the points. Peter Woit has shown no evidence in any of the discussions of the last few years of being able to do so. All Peter Woit’s ever done when asked to back up his claims is express his gut feelings (which he is entitled to) and prejudices against research in this area. His claims to know the outcome of all our research by saying that the program is a failure and that it cannot make contact with experiment have never been backed up with any more than vague assertions (and personal abuse when challenged)… Have a read through this thread as a good example, and the several others we’ve had before for further example. The bottom line is that nobody knows whether string theory is right or wrong because it is very much a work in progress. Suggested course of action? We all need to get on with our research and let others get on with theirs rather than
lying aboutknowingly stating incorrectly our knowledge of the outcome of what the others are working on in an effort to poison people against it.It is this misleading inconsistency of Peter Woit’s position (vs what he can scientifically demonstrate) that is so disturbing to some, since many in the general public (and further) are unable to tell the difference between his expression of dislike of a program of research vs an actual scientific demonstration. This has been used to his advantage (and his publishers and the press) to confuse a great many people. While I agree that research in string theory has sometimes been presented as further along than it really is, I don’t think that the honest person’s solution to this problem is a campaign of malicious misinformation.
Best,
-cvj
Dear mighty Hero,
Woit’s argument is just a popular scientific argument (of the kind you can find in these blog discussions, or in other popular books about string theory) so it is probably different than a technical scientific argument from a physics paper (not to speak of an argument of a technical paper by eminent people like these guys).
Anyway, if you meant to say that Woit’s concerns about supersymmetry-breaking simply do not take into account various new mechanisms that are being discovered, like those described by ISS then this is an interesting point that indeed refers to one of Woit’s point.
If you meant to say by your response that Woit’s writing deserves no response, then this is a perfectly reasonable approach. You may well choose not to respond. But if one choses to respond to Peter on more or less the same popular/scientific level, then referring to the different issues Woit raises in Chapter 12 can be helpful. (And I do not remember it was done systematically on these infinite blog discussions.)
1) A vacuum that has baryon-number violation at the electroweak scale is not anthropically allowed.
2) A vacuum that has baryon-number violation at the string, unification, or Planck scale is anthropically allowed, and probably in agreement with experiment (though details matter).
So, the question becomes, what fraction of string vacuua that reproduce the Standard Model at and below the electroweak scale also have baryon-number violating interactions at a scale that is both well above the electroweak scale (so that the baryon violatin is anthropically allowed) and well below the string/unification/Placnk scale (so that the baryon violation would be in disagreement with experiment).
Peter claims to know that the answer to this question is “almost all”.
In fact, the answer to this question is completely unknown.
My personal guess is “almost none”, because I think it’s hard to generate scales below the string scale, and getting the vacuum to do this once (the electroweak scale) is probably much easier than getting it to do it twice (the electroweak scale and some intermediate scale of baryon violation).
Dear Gina, if you wish to have a vague idea how a scientific argument connected with supersymmetry looks like, click at this link
http://arxiv.org/abs/hep-th/0602239
and then click at ‘PDF’ on the right side. Let us hope that you will see a certain difference between a scientific argument and something that is not one.
Dear Peter,
Yes, I would say intersecting brane models predict perturbative baryon number conservation. The reason is that in these cases the SU(3) comes from U(3) = SU(3) x U(1)_B, and so baryon number is present in the model as a gauge symmetry. Most U(1)s in interesecting brane models are anomalous, and in that case the U(1) survives as a perturbatively conserved global symmetry. This applies to IIA/IIB intersecting brane worlds. It does not apply to heterotic models, because the SU(3) comes from the larger GUT gauge groups, and there is no extra U(1)_B symmetry in the low energy theory.
I do not in the slightest understand why you think anonymity (on *blogs*) is unprofessional or unethical.* On the contrary, it allows the science to stand by itself; the correctness of the argument is divorced from prejudices about the author.
piscator
*this is not defending anonymity as a cover for personal attacks.
Woit’s chapter twelve
I looked again at Woit’s book and it seems to me that Chapter 12 titled “string theory and supersymmetry: an evaluation” can be regarded as what Clifford refer to “scientific argument” against string theory (and supersymmetry).
(Essentially only this Chapter plus a few paragraphs on the landscape which qualify to this description, as the rest of the anti string theory part consists of philosophical considerations, polemic and various anecdotes which are of some interest but of a very different nature than a “scientific argument”.)
I refer only to pages 161-187 as the last pages of Chapter 12 are again gossip-wise description of connections between mathematics and physics.
Of course, a lay person is expected to read earlier chapters before reading Chapter 12 and even so it is not easy to read; but experts can jump right to it.
My hunches reading this chapter were that
a) it is well-written and overall serious.
b) That the concerns Peter raises are overall familiar and his interpretation is just much more negative than those of other physicists. (BTW, regarding supersymmetry Peter is skeptical but undecided.)
c) That Peter does not mention various positive development in string theory that are believed to represents solid new insights of physics (regardless of the fate of other insights from string theory,) like various notions of duality.
However these are very circumstantial impressions. I do not think the arguments of this chapter of Peter were rebutted (or debunked) in an organized way in the blog discussions, or the thousands words Clifford wrote. (Maybe they were considered by Aaron Bergman or by ML but I don’t remember, and it is probably hidden among much other stuff.)
One interesting comment is that Peter refers in this Chapter to the “finiteness of string theory” as overall a positive support to ST so his approach is more reasonable on this issue than that of Lee as well as than his own approach in the marathon debate on this particular point that took place here on “Asymptotia”.
Anyway, comments or links to comments on Woit’s “Chapter Twelve” will be much appreciated.
Anomalous Cowherd (whoever you are),
Your argument that the anthropic landscape giving a prediction that is off by 15 orders of magnitude is a big achievement because it improves on some other argument that is 63 orders of magnitude off reminds me a lot of supersymmetry fans who argue that it’s a point in its favor that it naturally gives a CC off by 60 orders of magnitude instead of the 120 without supersymmetry. Both are equally ridiculous attempts to defend the indefensible.
mark and Mark,
I think both of you are referring to studies of string backgrounds that are designed to match the SM, and to suppress non-SM effects to match the fact that they haven’t been observed. Sure, if you assume that the landscape is statistically peaked on these backgrounds, with only the SM at low energies (or MSSM), everthing else happening at a very high GUT scale, then you can get suppression of proton decay. But my point is that there is zero evidence for this. What you are doing is just putting in as an assumption that the statistical behavior of the string landscape agrees with experiment. This just contradicts what is known about the string landscape (pick a generic choice of gauge group and representations allowed by the background, with generic scales of symmetry breaking, then I see no reason for baryon number conservation in the low energy theory).
Sure, you can say that “it’s just too early to tell”, that we’ve got to put in the exponentially large number of person-years of work needed to investigate the properties of the exponentially large number of backgrounds, before we can even try and accurately do statistics. The problem with this is that before you put a lot of effort into doing more calculations of a sort that you have already done a lot of, getting the wrong result, you have to have some argument for doing them better than the current argument, which is not much more than: we don’t want to admit failure, so we’re going to keep doing this no matter what.
Jacque Distler:
Italicized is my addition.
#84Tony Smith:
At anytime, if this process is fruitful “the others(Lubos Motl, Urs Schreiber, Aaron Bergman, and others)” could have step in to highlight the ideas behind this thread. That string theory is indeed “not whithering.”
IN this regard
Just a minor point about quoting people. To Gina’s regard, this maybe the “latex sand box” idea as well which can help educate the internet in terms of html development. There are ways to highlight this by blockquoting, italicizing or putting in bold
Tony,
There are already models derived from string which are able to get the standard model gauge group, three generations, gauge coupling unification, and the correct fermion masses for specific choices of moduli. The problem is in showing that the moduli will indeed take these values, i.e. moduli stabilization.
Plato says that by noting a lack of interest by the string theory community in my model I am
“… assuming that all the underlying work is devoid of the necessary physics that would have required any model in this case(string theory) …”.
No, I am not “assuming” that my model “… is devoid of the necessary physics … required …[of]… any … string theory … model …”.
To the contrary,
I am stating that the model was constructed during a discussion in 2004 on sci.physics.research and sci.physics.strings with Lubos Motl, Urs Schreiber, Aaron Bergman, and others,
and
that the model so constructed had the right first-generation fermion particles and antiparticles and the right Standard Model gauge groups, and an 8-dimensional spacetime that, if represented as a Batakis Kaluza-Klein spacetime, allows Hashimoto, Tanabashi, and Yamawaki ( see hep-ph/0311165 ) to calculate, for a Tquark condensate Higgs model, a Tquark mass of 172-175 GeV and a Higgs mass of 176-188 GeV
and
that the only negative criticism was by Lubos Motl who correctly pointed out that the model does not have conventional supersymmetry and is complicated (neither of which criticism seems to me to be fundamentally fatal).
If the conventional string theory community wishes to ignore that model, and to support Cornell in its blacklisting of me from the arXiv, that is a decision made by that community,
however
it seems to me that by doing so they might be missing an opportunity to show an example of how string theory can produce calculations (Tquark mass) consistent with Fermilab data and (Higgs mass) that can be tested by LHC,
thus refuting claims that string theory is “Not Even Wrong”,
and
I am stating that I feel that the decision of that community is not in its own best interest, either with respect to the current “Not Even Wrong” debate or with respect to how that community and that decision might be regarded by history.
Tony Smith
Tony Smith:
I think by stating “that” you are assuming that all the underlying work is devoid of the necessary physics that would have required any model in this case(string theory), not to have been supported by the science in it’s progression? How did you get there? Has perspective not been pushed back to the microseconds of the universe in expression?
I would suspect, any busy scientists would equate this to another agenda knocking on the door. Of course without having understood myself the connection to the reality you are speaking of, I understand “it is necessary,” as so many others understand, it is necessary.
What? Your space of possible vacua only obeys classical logic?
Peter wrote, “In A and B, all you are doing is pointing to mechanisms for suppressing proton decay. They’re not generic in the space of all known string theory backgrounds.”
First of all, we do not know whether or not this is true. It seems likely, but we don’t know. So, more work needs to be done to find out.
And, even if it’s true, it’s not necessary that proton decay be suppressed in all or most vacua that otherwise match the Standard Model. It is only necessary that either it is suppressed, or is so unsuppressed that those vacua are anthropically disallowed.
62 – Peter Woit Sep 22nd, 2007 at 8:08 pm writes:
“Your number of 10^24 years for the Goldhaber argument didn’t sound right to me, so I just checked it. All other sources give it as 10^16-10^17 years. ”
The number that I heard quoted was from an IMB talk 20 years ago, and I haven’t looked up a written attribution of the Goldhaber argument; you don’t give the attribution for the numbers that you quote, but for the sake of argument let’s assume that the numbers you present here are correct. Now let’s use standard dimensional analysis to estimate the degree of suppression of proton decay that is implied by the anthropic requirement of our continued health, and by the direct limits from Super-Kamiokande:
– The proton mass is 1 GeV; a fraction of order unity of this mass is dumped in any of the decay modes of the proton.
– The uncertainty principle then gives a corresponding expected lifetime of order 10^{-24} seconds, in the absence of anthropic selection (or dynamical suppression, but we’re discussing the strength of anthropic selection here). We see lifetimes of this order inferred from the widths of hadronic resonances [eg. the Rho or the Delta] so this is certainly the correct order-of-magnitude dimensional estimate.
-One year is of order 10^[7} seconds [strictly it’s about 3 x 10^{7} seconds, but I’ll be conservative].
-So 10^{17} years is of order 10^{24} seconds
-ie. 10^{17} years is 10^{48} times the dimensionally estimated lifetime of the proton in the absence of anthropic selection (or dynamical suppression, but we’re discussing the strength of anthropic selection here).
– The direct Super-Kamiokande limit is 10^{32} years, or about 10^{39} seconds.
-So the direct Super-Kamiokande limit is about 10^{63} times the naive dimensional analysis estimate for the lifetime of the proton.
We can conclude then, that compared to the dimensional analysis estimate of the proton lifetime with unsuppressed baryon-number violating interactions:
[1] Even using YOUR numbers, anthropic arguments would imply a necessary suppression of the decay rate [or enhancement of the lifetime] of the proton by 48 orders of magnitude.
[2] Direct limits from Super-Kamiokande imply a necessary suppression of the decay rate [or enhancement of the lifetime] of the proton by 63 orders of magnitude.
Again, I don’t personally think that anthropic considerations directly select for the lifetime of the proton, but as long as we are discussing this as a hypothesis, 48 (by your numbers) out of the 63 orders of magnitude needed are already required for anthropic reasons. This sounds more like a success than a failure; to try and quantitatively argue that the difference between 48 and 63 is significant, one would, at the very least, need to establish: (a) that in the model class under consideration the proton lifetime was not correlated with other quantities whose anthropic determination was responsible for the extra proton lifetime, (b) what the “a priori” distribution of the predicted parameters was, to quantitatively understand what “out in the tail” means, and (c) that there are not orders of magnitude stronger limits on proton decay lifetimes from the paleobiology of the origin of life on earth. In the absence of such a determination, if you really insist on using the proton lifetime as a test of anthropic reasoning, at our present level of understanding it’s hard to see how one could not regard it as a test that anthropic arguments pass.
Peter:
“In A and B, all you are doing is pointing to mechanisms for suppressing proton decay. They’re not generic in the space of all known string theory backgrounds. ”
Looks like in Type IIA with intersecting branes it is naturally suppressed. This is also true for M-theory on singular G2 manifolds (dual to the Type IIA orientifolds with intersecting branes).
Peter, could you please point to a class of backgrounds which can accomodate SM but where the proton decay is not suppressed?
Thank you!
Jacques,
So funny to be accused by you of being someone quick to jump to personal insults…
I was not claiming to reproduce the Dine et. al. argument. Actually I think the problem is more general and independent of the question of the supersymmetry breaking scale.
In A and B, all you are doing is pointing to mechanisms for suppressing proton decay. They’re not generic in the space of all known string theory backgrounds. You need to come up with an argument for why one of them is statistically favored over the more generic case. I haven’t seen any such argument other than wishful thinking.
Face it guys, the excitements we all had with the longish threads of heated debates regarding ST are, to a large extent, over. As much as we can try to revive it it will not be the same. But discussing weblogs’ rules and ethics and styles and behavior (and fonts) is a nice idea. These are exciting issues and new insights are even more likely to emerge. Maybe as two prominent bloggers (with different style of blogging) Peter and Clifford can do something, e.g., devote special posts, to these issue. (I recommend a strict ad hoc rule of not mentioning string theory.)
Always quick to jump to personal insults, aren’t you, Peter?
Anyway, for the edification of others, let me spell out the argument that Peter is, in his own inimitable fashion, mangling.
Consider the following set of logical propositions.
1) String theory, specifically, its prediction of a landscape of vacua is a correct description of the world.
2) “You can get just about anything you want” on the landscape. That is, the landscape of vacua more-or-less densely fills the available Standard Model parameter space.
3) The only mechanism that selects among the available vacua is the Anthropic principle, which cuts out an anthropically-allowed swath through the parameter space.
4) The proton lifetime is far longer than the anthropic bound. Ergo, it cannot be explained by anthropic selection, and we have reached a contradiction.
Clearly, Peter would like to conclude that this means that proposition 1) is false (and, indeed, it might be false). But that does not follow, and was not what Dine et al argued.
Rather, it is assumption 2) that is suspect. I argued that it is suspect in much greater generality in the comment thread I linked to above. But, in the specific case of the proton lifetime, we already have seen two mechanisms, discussed in this thread, either of which could constrain the proton lifetime to be far longer than the anthropic bound.
A) If the supersymmetry-breaking scale is high, then the low energy theory has an accidental global U(1) symmetry which forbids proton decay.
B) Even if the supersymmetry breaking scale is low, it could be that the details of obtaining the standard model on some intersecting branes (at a singularity) impose a discrete R-parity, which, again, would suppress proton decay.
There are quite a few string theorists who do not accept the anthropic approach that is strongly advocated by some other string theorists. There are probably some who while not dismissing such an approach altogether feel that string theory is not sufficiently developed to start working seriously on the anthropic direction. There are probably some who think that even if we may gain some insights working now on the anthropic landscape it is not the most important or deep part in current string theory research and in view of the state of string theory the insights we may gain are rather tentative. (Actually this is my own lay person impression.) All in all, I do not see why an attack on the anthropic approach which is debated within string theory can be regarded as a critique on string theory as a whole. (Unless Peter plans is to go after each individual string theorists and explain why her or his specific projects are misguided.)
Also Peter wrote “You need to show that among all the possible string theory backgrounds that are anthropically allowed, ones with baryon number violation are statistically suppressed by a huge factor.”
This is a little technical point but I do not understand: why do you need it supressed by a huge factor? Why yay, 1:2 factor is not good ?
piscator,
You’ve explained well why anonymity is convenient: you can make arguments without worrying that they’re uninformed or dumb, and thus would reflect badly on your reputation. This still doesn’t explain why you think it’s either ethical or professional behavior.
So, is your claim that string backgrounds predict (perturbatively) exact baryon number conservation? According to you string backgrounds either have fast proton decay (not seen), or no proton decay. So, if experimentalists see a proton decay, that means string theory is falsified?
Jacques,
You seem to have trouble following an argument that has more than one part to it, but I really think you should concentrate and try. I wrote out clearly an argument here that doesn’t fit in one phrase of a sentence, see if you can follow it.
I also think you should consider exercising some more self-restraint in the area of html tags. I guess the bold-facing of phrases is supposed to indicate that they are my views, probably even quotes from me. I know you’re very fond of taking things I write out of context, often changing the wording, then putting the result in between quotes, then using it to sneer at what an idiot I am, a fool who makes arguments that are easily demolished. Your use of bold-face seems to be a variant of this. I think you should stick to the quotes, it’s a standard convention.
dear Peter,
i meant something a bit stronger than that one can construct models where baryon number conservation applies. in the intersecting brane setup, it’s hard for it not to apply – a stack of three branes always carries a U(3) gauge symmetry, which includes the U(1) of baryon number. this doesn’t hold for lepton number since then su(2) can be sp(2) without an extra U(1) factor to complete to u(2). anyhow, the existence of perturbatively conserved baryon number seems quite natural. I have no idea what a probability measure on the landscape would look like, but if I did I would expect two delta functions, one for which the proton decays very rapidly and one for which it never decays.
on anonymity: there are perfectly good reasons for it, and I prefer it. If I write a paper I spend months ensuring that I am happy with what I am writing. If I am commenting on a blog I spend minutes. There is a lot of overlap between axiv and blog readership; i’d rather be judged by what i contribute to the former rather than the latter.
piscator
Plato quoted me as saying
“It is true that “some in the … string theory … community may feel that it isn’t necessary to explain physics … “,
which would be sad for the future of theoretical physics.”
and then asked
“… On condition that we accept what? …”
The quote of me by Plato was from my comment 59 here, in the context of the failure of string theorists to evaluate a model (see my comments 42 and 43 here) that may connect string theory with physical reality
and
was constructed in a discussion in 2004 on sci.physics.research and sci.physics.strings, so the details of its construction are open on the web for everybody to study.
The only criticism I have received of the model was from Lubos Motl, who correctly noted that the model is not conventionally supersymmetric and is complicated.
I do not consider either to be fatal flaws.
My criticism is of
1 – the lack of interest by the string theory community in a model that might show how string theory is connected to physical reality and
2 – the fact that I am blacklisted by the Cornell arXiv and so prevented from writing about the model there.
I suspect that 1 and 2 are not unrelated to each other.
Tony Smith
It’s really quite amusing watching Peter Woit attempting to play both sides of the street (The landscape renders string theory inherently unpredictive about particle physics at accessible energies and, in nearly the same breath, The landscape yields predictions which have already been falsified.). Since I’ve already rebutted the former (see also the followups: I,II,III,IV,V,VI), I’ll leave it to others to rebut the latter.
Anonymous hero,
I wasn’t claiming priority on that argument, thanks for pointing to the Banks, Dine Gorbatov paper, which I should have mentioned since that’s where I first heard this argument. Susskind doesn’t actually address the proton lifetime problem, he just addresses the assumption by Banks, Dine, Gorbatov that supersymmetry is broken at low scales. He points out that landscape statistics may actually predict breaking at high scales, not low, but the fact that even this can’t be resolved is good evidence that landscape statistics can’t predict anything (this should be about the easiest case). If you take Susskind’s argument seriously, if the LHC sees supersymmetry, then Banks, Dine, Gorbatov works, so the Landscape is dead. Steinhardt makes the point in his edge discussion that no one is taking these arguments seriously, just modifying them as needs be to make sure that the Landscape never can be falsified.
Piscator,
I’m not saying you can’t construct models that preserve baryon number, just that, if you start counting anthropically allowed models (despite the fact that there probably is no consistent way to do this counting), there’s no reason for baryon number conserving models to be suppressed in the count by the huge factors that would be necessary.
By, the way, I think people being willing to engage in a serious discussion of these issues is great and I’m happy to participate, but it’s kind of annoying not knowing who one is talking to….
Dear Peter,
Intersecting brane worlds are one of the large(st ?) class of models people study in building Standard Model-like models. The QCD brane carries a U(3) gauge group, the SU(3) becomes QCD and the U(1) is baryon number. If the U(1) is anomalous then baryon number survives as a global symmetry (and at high energies is a gauge symmetry). Therefore from a model-building perspective, having baryon number as an exactly conserved global symmetry is really quite easy.
piscator
Just a trivial point.
The idea that the longevity of the proton falsifies the anthropic principle hasn’t been found by Mr Woit but by Banks, Dine, Gorbatov in 2004
http://www.iop.org/EJ/article/1126-6708/2004/08/058/jhep082004058.pdf
Leonard Susskind replied to it here:
http://arxiv.org/abs/hep-th/0405189v1
Mark,
The argument you need to make is not that if a string background looks exactly like the SM at observable energies then baryon number violation will be suppressed statistically. You need to show that among all the possible string theory backgrounds that are anthropically allowed, ones with baryon number violation are statistically suppressed by a huge factor. If you actually look at classes of backgrounds that people study, this just isn’t true (except to the extent that, within a class, they only look at phenomenologically viable ones, e.g. by picking out ones that look like then SM and have a desert, in order to avoid having any non-SM effect actually be observable…).
Mark:
Layman asking.
What kind of tools? Is not “mathematical construction” not important for that perspective in regards to Genus development, and “correlative development(?)” of that one string vacuo?
Thanks Mark for making clear the points we need to consider in face of what is constantly being bombarded by “other points of view.”
Tony Smith–
On condition that we accept what?
This is what is being portrayed as “being irresponsible,” while it is obvious such statements can serve to make the whole research avenue in string theory hopeless and “fruitless”:) E8’s flowering attributes…hmmmm….:)
“This method” is a continuing aspect met by “setting the conditions for acceptance,” while it is obvious that “Mark’s point of view” says otherwise.
The arguments should “set the parameters” and not be then subjected too the schism of thoughts about one’s “personal opinion.” One can support and bias opinion by what they then censor. It becomes a pretty clear picture from then on. Carries a certain “tone” to it:)
Then the public gets a “clear message” of the resulting area of research in the face of a personal opinion.
Peter, you can’t know whether the predictions work until you know what they are. While there are many speculations as to what the predictions might be, there are as yet no firm results. So your statement that “you get wrong predicitons” has no evidence whatsoever to support it. In particular, your claim that if the string landscape makes any predictions at all, then it gives an incorrect prediction of the proton lifetime, is flatly wrong. As I explained above, it’s entirely plausible that any vacuum that has a global symmetry (like baryon number conservation) in the low-energy effective field theory has that symmetry violated only by effects at the string or Planck scale; this would predict a proton lifetime that satisfies current bounds. But we don’t yet know if this speculation is right or wrong. More work needs to be done to find out.
Anomalous Cowherd,
Your number of 10^24 years for the Goldhaber argument didn’t sound right to me, so I just checked it. All other sources give it as 10^16-10^17 years.
I suggest that you very seriously consider stopping posting anonymous comments here, and put your name and reputation behind what you have to say. Doing so might encourage you to take some care to not make obviously false claims.
Anomalous Cowherd,
I don’t think you’re making any sense at all. If you have any ideas for an “anthropic” explanation for the proton lifetime, I suggest you publish as soon as possible, since many people will get very excited by it and you will immediately become a leading figure in the hottest field of particle theory.
Mark,
The argument I’ve given here can’t be news to you, I’ve made it many times on this blog and others, I think more than once in direct response to you. I think there are legitimate arguments that statistical “predictions” from the landscape can’t actually be sensibly made. My point is that these are the ONLY possible arguments, whether or not they work. You have two choices: assume they don’t work, then you can never predict anything, or assume they do work, then you get wrong predictions. My guess would be that they don’t work, but my point is that if you stipulate that they do, you get wrong predictions.
If you have a serious argument for why the anthropically allowed part of the string theory landscape has to have proton lifetimes at or above the current limits, I make the same suggestion to you that I make to Anomalous Cowherd. Go ahead, publish, and become a leader of the field….
In fact, some string theorists think that it is a red herring….
Eric said “… if string theory is correct then there should be at least one string vacuum which can produce all physics in our univserse in complete detail. …
Conversly, if we find such a vacuum it may have some special properties which may lead us to understand why it is chosen.
It may be that part of Woit’s complaints about string theory is that some in the community may feel that it isn’t necessary to explain physics that is operative in our universe …”.
The model in my comments above (42-43 in the present numbering) might show how to construct “at least one string vacuum which can produce … physics in our universe …”,
so
it is hard for me to understand why string theorists are not interested in exploring it in detail, especially since no one has yet shown it to be fundamentally flawed,
unless
it is true that “some in the … string theory … community may feel that it isn’t necessary to explain physics … “,
which would be sad for the future of theoretical physics.
Tony Smith
There is no “prediction” of the proton lifetime from the landscape that has been “falsified”. (Peter likes to insist, on the one hand, that string theory is incapable of making predicitons, and, on the other, that it has already made predictions that have been falsified.)
As of now, we have no idea what features are or are not common to landscape vacua (if any) that reproduce the Standard Model to sufficient accuracy. It may well be that, in all or almsot all such vacua, all baryon-number-violating effects arise only at the unification or the string or the Planck scale, which would make it within experimental bounds. In fact this seems to me to be the most likely possibility.
Eric, I agree completely that finding one string vacuum that matches the Standard Model would be a good and important thing to do. Experts tell me that this is a daunting task, and that they need better tools to be able to do it without extensive trial-and-error constructions.
#53
“There’s no anthropic reason for the proton lifetime to be as long as it is, and there is no plausible argument I know of that says that string backgrounds should conserve baryon number. The observed value of the proton lifetime is very far out in such a tail. This prediction has flat out been falsified.”
Folklore has it that in the 1960’s Maurice Goldhaber argued for a lower bound on the lifetime of the proton of order 10^24 years from the fact that we don’t die from the health effects of radiation from decay of protons in our own bodies and our environment [the phrase that I heard attributed to him was that we feel the longevity of the proton “in our bones”]. Limits on ambient proton decay radioactivity may be even more stringent from survival of RNA and DNA when life started in the primordial ooze on planet earth [I don’t know enough biology/biochemistry to quantify this]. Are you so confident of your mastery of primordial biology that you can convincingly argue that this is hierarchically shorter than the proton lifetime limits from Super-K, which for the decay modes induced by the dominant dimension-five operators are of order 10^32 to 10^33 years? If not, then this could actually be argued to be a successful prediction of anthropic reasoning, rather than a prediction that has “flat out been falsified”. I wouldn’t make that argument personally, but it seems to me that your counter-argument is at least as suspect.
Regardless of whether or not the anthropic landscape is true, if string theory is correct then there should be at least one string vacuum which can produce all physics in our univserse in complete detail. Even if we have no idea why such a vacuum is chosen by nature, it still seems to me that finding it would allow us to understand everything about the universe we live in. Conversly, if we find such a vacuum it may have some special properties which may lead us to understand why it is chosen. It may be that part of Woit’s complaints about string theory is that some in the community may feel that it isn’t necessary to explain physics that is operative in our universe, and these people are resigned to the antrhopic principle.
Anomalous, I personally find much more vitriol and hostility in post #54 than in #53, and more reasoned argument in #51—#53 (and some others above) than in your posting immediately preceding this. Whether the reasoned argumentations presented there are correct or not is a different story. But that’s what reasoned argument is for, isn’t it? To try and find out which arguments hold water and which don’t.
Re: Posts #51 and #52
Dear Mark
Thanks for the insightful analyses, clearly articulated. But are you sure that you really want to be doing this again? The vitriolic attacks that seem inevitably to blight any blogosphere discussion of the present state of theoretical physics, seem to be driven by hostile feelings on the part of the critics, towards the research programs of others. It seems to me unlikely that any manner of reasoned argument will persuade people who seem to have so much emotionally invested in the prospective failure of other peoples’ research.
In this regard, it seems to me that Wiitten’s approach is the wisest; stick to the physics and don’t get distracted by noise on the internet. [Feynman famously put it more bluntly: “shut up and calculate”]. My general observation is that people are most inclined to spend time criticizing others’ research, when they are unhappy with the progress of their own; to waste time debating them risks reducing your effort on your research to the level of their effort on their research. I’m sure that you have better uses for your time.
Remember: “living well is the best revenge”.
Mark,
I think I’m repeating exactly the same argument I’ve made many times before, and you don’t seem to have paid attention to it any of those times, but here it goes again. I don’t think it’s actually substantially different than the one David Gross and Paul Steinhardt are making on the issue of the anthropic landscape. You might want to try stopping by Gross’s office, telling him that he’s promoting an ideology that is unscientific, and arguing the issue with him.
I have nowhere said that the landscape scenario is “impossible”. It’s a logical possibility. But there are lots of logical possibilities that can’t be scientifically investigated. It’s a logical possibility that we are a simulation created by higher beings, and the only explanation of the standard model parameters is that those being chose them, for reasons we can never know. It’s a logical possibility that standard model parameters are all environmental, and we can’t ever explain their values, since they come from some earlier history we have no access to.
For a hypothesis to be scientific, it has to come with some way it can be convincingly tested, at least in principle. This is what the whole argument here is about: do the people promoting the anthropic landscape have a plausible argument for how to convincingly test this scenario experimentally, even in principle? If they do it’s science. If they don’t, they are scientists engaged in pseudo-scientific argumentation. I’ve read the papers of the people making these arguments very carefully, and at length on my blog and elsewhere have argued that:
1. The only testable predictions you can hope to get out of the anthropic landscape are the statistical ones that predict that we will see values of that are not far out in the tails of probability distributions. There’s no anthropic reason for the proton lifetime to be as long as it is, and there is no plausible argument I know of that says that string backgrounds should conserve baryon number. The observed value of the proton lifetime is very far out in such a tail. This prediction has flat out been falsified.
2. The string theory landscape is a classic example of scientific failure. Often scientific ideas fail not because they are rigid enough to make predictions that are falsified, but because you can get almost anything you want out of them by adding in more and more complicated structure. Simple versions of the idea don’t work, people look at more and more complicated versions, until the whole thing collapses of its own weight. This is a very common form of failure of a research program, and it is what has happened here. The only thing unusual is the lengths people are going to in order to avoid admitting this.
Paul Steinhardt in the discussion at http://www.edge.org that is up now makes precisely the points I am making: the anthropic landscape is not a valid scientific research program, it is what he calls one that has “crashed”, i.e. failed definitively.
As for whether the “overwhelming consensus” of the physics community is that string theory is the most promising thing for people to be working on in order to make progress towards unification, I just don’t think this is true, and it’s also not especially relevant, since science is not a popularity contest. During the 1960s the “overwhelming consensus” was that QFT could not describe the strong interactions, but it was wrong. If you restrict attention to people working on string theory, sure they may have an “overwhelming consensus” among themselves but I think that a very significant portion of the particle physics community doesn’t share in this consensus. Many, many of them think that string theory unification is an idea which has been tried but hasn’t worked out, and now shows every sign of conclusive failure. I don’t have any numbers on this, it would be interesting if someone could figure out how to gather them in a sensible way. If this had been done over the past twenty years, I don’t know what the absolute numbers would have been, but I am quite sure that the time derivative is negative, and if you extrapolate to the future you’ll find this “overwhelming consensus” disappearing if it has not already done so.
Here’s another point. What if the landscape is correct? That is, our universe really is a “pocket universe” in a vastly larger multiverse that populates a landscape of metastable vacuua in the enormous moduli space of metastable string vacua. Furthermore, the properties of our universe are just randomly selected, with anthropic filtering so that we can be here. And, even worse, there is no particualr correlation among parameters in the landscape, and so no fundamental explanation of any aspect of the Standard Model is possible.
I think this might turn out to be right. If it is right, how would we ever know?
Well, we wouldn’t ever know for sure. Circumstantial evidence in favor would include progress (possibly slow) in better understanding the fundamental, underlying basis of string theory, with clearer and deeper understanding of its mathematical structure and physical possibility. Also, continued failure of all other programs to do any better, and lack of progress in better understanding the fundamental, underlying basis of each alternative program, or the inability of alternate programs to clearly reproduce the Standard Model plus gravity as an effective field thery.
That would be disappointing, of course. It would make physics a lot more like most aspects of human life, where conclusive proof of anything is awfully elusive. But people like Peter seem to have an underlying notion that this scenario is not just unpleasant, but actually impossible, that there must be a fundamental explanation of the parameters of the Standard Model, and that any research program that looks like it’s going in the opposite direction should be dropped immediately.
This is an ideology which is, in my view, inherently unscientific, since it assumes a result (that there is a fundamental explanation of the parameters of the Standard Model) that is, in fact, still very much open to legitimate scientific doubt.
I don’t know why I do this, but I’m going to comment on these issues again …
Peter argues that string theory has “failed”. For the sake of argument, I would like to stipulate this. It is definitely true that string theory has not yet produced a clear explanation of any aspect of the Standard Model (gauge group, field content, values of any of the parameters), and this is disappointing. How likely string theory is to succeed in this sense in the future (and if so, when) is a matter of pure conjecture, and people differ quite a bit in their opinions in this regard.
So, what is the appropriate reaction to this stipulated failure of string theory?
One possible response is to strike out in a completely different direction. This is Peter’s response; he says he is making “slow progress” in his research. Of course, unless and until this program produces a clear explanation of some aspect of the Standard Model (gauge group, field content, values of any of the parameters), it has the same stipulated failure as string theory. How likely Peter’s program (or any other program) is to succeed in this sense in the future (and if so, when) is a matter of pure conjecture, and people differ quite a bit in their opinions in this regard.
Each individual researcher must, then, make a decision as to the best direction to pursue. The overwhelming consensus at the moment is that the circle of ideas collectively known as “string theory” constitutes the most promising framework. Not everyone agrees, of course, and it may well turn out that some alternate program will succeed. Unless and until that happens, all these arguments will continue to go in circles.
Hi Telureo,
You said:
Unthinkabe? Then, with all due respect, you’ve not been thinking very hard, or perhaps you’ve been listening to too few string theorists. Such a statement from an active string theorist (several, I suspect) could have been heard any number of years ago. I’m guessing that you’re confusing the motivations you read about in popular articles written by a few people with the motivations that bring string theorists to work on their research everyday. They do not necessarily overlap. The physics is so rich and varied that there are many many ways of coming to it. The motivation is to describe and understand nature as best we can, not to march along indefinitely with a fixed idea of how we want nature to be. This is the way science has always proceeded. Nothing new there.
Cheers,
-cvj
Many red herrings seem to be washing ashore these days. Now we learn that computing the electron mass is a red herring, computing the CC is a red herring, and TOEs are red herrings. I dare say that this red trickle was in no small measure motivated by just one piece of experimental data: the observation that the CC, contrary to everyone’s expectations, is positive. And that’s just an astronomical observation.
With a steady flow of high quality accelerator data hopefully soon to appear on line, the red trickle is threatening to become a red tide. I wonder how many red herrings the LHC is going to bring. Maybe even a red whale or two.
Thanks for your support, Anonymous Cowherd. I’m rather busy making tea right now, but when I come back, I’ll clearly demonstrate that, although I am just a lonely voice in the academic wilderness, my aim is just to Make The Madness Stop.
The very basis of science funding may critically depend on my efforts.
Whoa – I take a brief holiday (they do smoke a lot more in Canada, don’t they?)and return to find the teacup as stormy as ever. At a more mundane level zeta function regularisation annoys the uninitiated in almost every field in which it finds application. I used it in the analysis of an interferometric SAR system, and got real grief for my pains. Though (and I hope this is right, Clifford) 1+4+9+16+..=0 does rather astonish. Secure in the knowledge that this stuff is OK with the stringers I can now follow Molesworth and state categorically that ‘eny fule kno that’1+4+9+16+..=0.
Mathematical consistency.
If this is not of value then what is in any theory?
“The Trouble With Physics,†by Lee Smolin, Index page 382, Mandelstam, Stanley, and string theory finiteness, pages 117,187, 278-79, 280, 281, 367n14,15
The discussion with regards to Lee Smolin helped direct our attention to the very last statement made by Lee, to have shown, that an extension was made.
Lee Smolin:
Lee Smolin:
Jacques Distler :
So in principal, “mathematically,” we see where progress is made. Peter Woit had to accept these changes. 🙂
Reading such a statement from a string theorist would have been unthinkable some years ago. Maybe the string and anti-string camps are beginning to converge?
Clifford wrote “The whole “Theory of Everything†business is a red herring.”
Does this mean that the TOE is a theory of Quantum Aquatic Chromodynamics?
e.
With respect to my immediately previous comment,
maybe I should also say that, using an 8-dim Kaluza-Klein spacetime (like that of Batakis in Class. Quantum Grav. 3 (1986) L99-L105),
Hashimoto, Tanabashi, and Yamawaki in hep-ph/0311165 calculate, for a Tquark condensate Higgs model, a Tquark mass of 172-175 GeV and a Higgs mass of 176-188 GeV,
thus
making contact with Fermilab collider Tquark results
and
making a prediction for Higgs at LHC,
which
if my immediately previous comment is realistic, establish such contact and prediction in terms of string theory.
Tony Smith
As to “Whither String Theory”,
back in March 2004 in a sci.physics.research thread Re: photons from strings? John Baez asked:
“… … has anyone figured out a way to … start with string theory … to get just photons on Minkowski spacetime …”
and there was a discussion among Lubos Motl, Urs Schreiber, Aaron Bergman, et al, and me, that continued in 2004 on sci.physics.strings.
A construction was suggested that started with old-fashioned 26-dim bosonic string theory
and
then using orbifold compactification of 16 dimensions to get 8 first-generation fermion particles and 8 first-generation antiparticles
and
then stacking 8-branes to get an 8-dim spacetime with the Standard Model gauge bosons.
If you look at the 8-branes as representing an 8-dim Kaluza-Klein spacetime a la Batakis (Class. Quantum Grav. 3 (1986) L99-L105), then you may have a string theory model that has a lot of realistic characteristics.
In that sci.physics.resesarch thread, Lubos Motl did not like the model (IIRC, he said it was not supersymmetric and was complicated, both of which are true),
but
kneemo said that it might be “… a nice formulation of (bosonic) M-theory (as Susskind refers to the 27-dimensional theory), from where we work down dimensionally …”.
I attempted to describe it in a paper on the CERN CDS EXT preprint server, where it is available as EXT-2004-031.
Do you think that such an approach might be a reasonable step in linking string theory to the Standard Model, thus refuting claims that all of string theory is “Not Even Wrong” ?
Tony Smith
Whoops… I should have said… the “loopers” who support Peter, since Woit is a particle theorist, not a gravity theorist.
Woit tells us what we want to hear:
I do rather ruthlessly delete comments submitted to my blog that are ill-informed and just add to the noise level, especially the large number from people who think that my blog is a good place to promote their personal “alternative†views about physics.
Ah, but you also “moderate” comments that are aimed to point out the ill-informed ideological dogma of your fellow loopers, whom you allow to take unsupported shots… because “you don’t want it to generate arguments that take away from the subject at hand”.
Course… you’re just as guilty of that as they are, and so your one-sided grunt sessions about the AP are just meaningless neodarwinian-like dogma that doesn’t match the observation, son.
Eric, I think that Anonymous Cowherd’s point was that the point attributed to JoAnne you mentioned, as well as most similar points in the world, are wrong. And it was not only a point but he also gave you the proof. For a method to distinguish a gluino from a KK gluon, for example, see
http://arxiv.org/abs/hep-ph/0605067
I believe that JoAnne’s point is that LHC will not be able to definitely distinguish between SUSY partners and Kaluza-Klein states associated with large extra dimensions.
Reading Peter’s comments in this thread, it seems to me that the question is if string theoreticians consider the prediction of HEP parameters (charges, representations, CKM matrix and masses) as a priority.
JoAnne writes:
“the LHC will not actually be able to determine whether or not the new particles it will discover (note the optimism here) are supersymmetric or not… absolute branching fractions, spins,etc…. are all for the most part out of reach for the LHC.”
I do not think that this occasionally expressed [largely in North America] opinion is entirely accurate. While LHC experimentalists have been largely preoccupied with getting the detectors built and commissioned, and they (and theorists providing support for their groups) have only recently started to do the requisite studies to demonstrate their ability to resolve these issues, the results that they are getting from those studies are much more positive than is often represented. For example take spin determination of candidate supersymmetric partners; on my desk I presently have the following selection of papers:
Barr:
hep-ph/0405052
hep-ph/0511115
Alves, Eboli, and Plehn:
hep-ph/0605067
Athanasiou, Lester, Smillie, and Weber:
hep-ph/0605286
Smillie:
hep-ph/0609296
Wang and Yavin:
hep-ph/0605296
Kilic Wang and Yavin:
hep-ph/0703085
Alves and Eboli:
arXiv:0704.0254
all of which seem to indicate that spins are NOT “for the most part out of reach of the LHC”.
We should also note that these studies are still in their infancy, and will really start developing when there is data to spur interest [for a recent historical example of this effect compare the theoretical predictions of the CMB temperature and polarization anisotropies before , and after, the initial detection of these anisotropies by COBE]. And with colliders it is true that often the final physics reach accessed far exceeds initial expectations; LEP is an example of this where the final precision far (!) exceeded the predictions in the original “Yellow Book” studies. LHC will have a 20 year research program, and the power and level of sophistication of the final analyses may far exceed our expectations today.
———————————————
Samantha writes:
“Although I work in an unrelated field, I have come up with some challenging and contraversial ideas about string theory that are going to upset those in the mainstream.
Unfortunately I have to go out for a bit, so I can’t discuss my ideas right now, but I just wanted you all to know that I know that you are wrong.”
Bravo! I can’t believe that readers here missed this satryical gem! You made my day…..
Thanks!
Hi Carl,
I just noticed that Robert has a nice post on regulating divergent sums here, which in turn will lead to a another post of interest.
I think that you’ve confused several things by the way, if you don’t mind my pointing them out
(1) Regularization in QFT has nothing to do with having a cutoff and making an effective field theory. They are issues that are often tangled up with one another, and this seems to really still trip up a lot of people, including the lay community, and even reasonably well trained students. so I thought I’d point that out here. I recommend some of the more modern presentations of QFT (such as Tony Zee’s book) for clarity on this.
(2) There’s nothing wrong with effective field theory, or more generally, effective theory. Arguably, that’s all we ever do in physics and all we’ll ever do.
(3) If string theory turns out to be nothing more than an efficient (and geometrical) way of generating effective theories, then who cares? As long as it helps describe what comes next in the physics that we want to explore beyond the currently known – I’ll take that in a flash.
(4) Combining (2) and (3): The whole “Theory of Everything” business is a red herring. The idea itself might have nothing whatsoever to do with Nature. We’re trying to describe Nature first, and if it turns out that we find a Theory of Everything (I don’t even know what that really means and have doubts as to whether it is anything but a charmingly naive idea) as a bonus, then great…. but the focus is to find how to put together the clues we have to understand nature at the next level. That’s really the best anyone can hope to do at any given point in the development of science. It’s ok to have hopes, of course… and different physicists have different hopes that motivate them. But not all those hopes will be borne out, and new ones will come along.
I made other remarks about Theories of Everything in a blog post here.
Best,
-cvj
Woit: I agree that zeta regularization in itself is not a sign that string theory (and those parts of QFT that rely on this technique, and similar stuff like dimensional regularization) is wrong, or can produce no predictions. My point is that zeta regularization is a sign that string theory is no better than QFT in that it is only another effective field theory. It cannot be any sort of a consistent and complete explanation. An energy cutoff is a sign of a theory that doesn’t work at high energies. These alternative regularizations are just mathematically ugly ways of avoiding having to directly describe a theory that doesn’t work at high energies. String theory cannot possibly be a “theory of everything”.
The reason I hang around here rather than on your blog is that this one is a lot more entertaining. It covers lots of subjects. It regularly has cool photos. The comments come from all sorts of people and it doesn’t keep rehashing the same stuff over and over.
And by the way, it is rather unkind to imply that I wish to promote my “personal “alternative†views about physics” by abusing your blog comments. My work is accepted by the physics community to the extent that I have been cited in 4 peer reviewed journal articles with four different authors. This is better than any crackpot. Do compare “4” with the number of citations your physics has picked up in the past year.
Since I’m a practical person who gets his hands dirty in industry, rather than an ivory tower intellectual, I have a useful and practical understanding of how to promote ideas. If I decide to promote my work, I will write a press release just like any other businessman. The title would be something like “Local Ethanol Engineer Finds Neutrino Mass Formula” and it would include links to the journal articles and probably a photo of me wearing a hard hat. I would send it to the Spokane Associated Press desk (which published a press release I wrote just a few weeks ago for my company). They would send it out on the wire and it would be picked up by a significant fraction of the world’s newspapers as a “man bites dog” story.
Dear JoAnn,
Are you basically saying that from the decay signatures we will never be able to distinguish say, a decay of a chargino from a gluino decay? And if there is large missing energy, would not it be a sign of SUSY?
Thank you!
Avoiding properly answering a straight physics question about your claims again, Peter?
-cvj
Clifford,
Your response speaks for itself. You don’t know anything about this subject, and that explains why it has not been possible to discuss it with you.
Avoiding properly answering a straight physics question about your claims again, Peter?
-cvj
Clifford,
When I first started trying to respond to your attacks on me and my book, I couldn’t figure out why it was so difficult to have a serious discussion with you on the topic. After you finally admitted you hadn’t read the book, hadn’t read Lee’s book, and had no intention of ever doing so, it became clear what the problem was: while you were attacking me as ill-informed, you yourself knew very little about what you were arguing about, and weren’t interested in learning more.
I’ve been equally puzzled by your response to any sort of serious argument I make about what the problems are with using string theory backgrounds to get unification. When I make such arguments here and elsewhere, I often get serious, well-informed challenges to my point of view, from anonymous and non-anonymous commenters. From Jacques Distler I get a serious argument, together with sneering insults. From you, I’ve never gotten a serious response, just the sneering insults. It just struck me that there’s an obvious reason for this, the same one as in the case of your comments on my book and Lee’s: you don’t know what you’re talking about.
Looking over your book, your many papers and your blog entries, I couldn’t find anything at all that shows any evidence that you know anything about that part of “string phenomenology” which is concerned with seriously trying to get the standard model out of a string background. You never mention anything about the various proposals people work on in this area, what the problems with them are, what the prospects are for somehow getting something predictive out of them, etc. For example, the “long detailed” blog posting on the landscape that you refer a commenter to here is certainly not detailed. There’s nothing much substantive in it except a popular-level explanation of what an energy functional for moduli is.
Besides the books critical of string theory, I’ve noticed repeatedly that you often mention in your blog postings that you haven’t read some book or article that you are discussing. One example I recall is that you haven’t read Susskind’s book. You seem to be remarkably uncurious about and unwilling to learn about a wide variety of things, especially things that don’t fit with what you would like to be true.
There’s nothing wrong with deciding not to spend the time to understand what is going on in the field of string phenomenology. Certainly there are better ways to spend one’s time, and it’s a legitimate complaint about my behavior that I have wasted too much of my life learning about this instead of pursuing my own research. But if you choose not to inform yourself about something, publicly attacking people who have as “ill-informed” is truly disgraceful and unprofessional behavior.
Can’t believe I am joining the fray here, but I gotta add my 2 cents and clear up the discussion on what the LHC can and cannot do. So here goes: The LHC will not be able to determine the mechanism that breaks supersymmetry. In fact, to be ultra-precise, the LHC will not actually be able to determine whether or not the new particles it will discover (note the optimism here) are supersymmetric or not. The LHC will be great at discovering new particles and will make gross measurements of their masses. Couplings, absolute branching fractions, spins, fundamental parameters in the Langragian of the underlying theory, etc. are all for the most part out of reach for the LHC. For these types of measurements you need experimental precision and the knowledge of the initial quantum state. I am as excited about the LHC as a person can be – I believe it will revolutionize our field. However, the stream of uninformed hype of what it can do is starting to get to me.
Hi Tilman Riemenschneider,
I don’t think that work on the landscape is disreputable. Where did I say anything like that? In fact, I did an entire (long detailed) post about the landscape and what motivates the research. See here. I don’t happen to work on it, and I think that there are several issues to be addressed about the basic question of what string theory really is before one starts declaring that the landscape is the chief issue concerning connecting strings to nature. It is important for people to work on it and explore it in the best way they see fit. Several are doing that. I’ve pointed out that there are several other efforts in string theory going on that are hugely important too. I don’t see what is wrong with doing that. The opposite is to characterize all that is important in string theory as some narrow range of effort and then criticize that effort. That’s Peter’s approach. That seems wrong to me.
Your characterization of the possible application of string theory to QCD and mathematics as minor issues is, I have to say, seriously misguided by the way. We’ll have to disagree on that.
Thanks,
-cvj
While I am inclined to take Clifford’s side in this dispute, there is one aspect of his approach that I find disturbing. He is always saying, “look, not all of us are working on the landscape! See, there are these other cool things like the [possible] application of AdS/CFT to heavy ions….”
[a] Does Clifford really think that the landscape is so disreputable? If not, he should make this clear, because I have the strong impression that he does.
[b] If the landscape story is really as screwed up as PW [and many others] think, then does Clifford think that he can just ignore this? Can one’s daughter be just a little bit pregnant?
Just to be clear: I myself think that work on the landscape and related issues is perfectly respectable. [Though I don’t think that the landscape idea really works as usually advertised.] And I think that the way to defend string theory is to defend the landscape head-on, not by means of distracting talk about how wonderful string theory has been for mathematics or heavy ions, which really are very minor issues.
Name-calling. That’s really your response, instead of sharpening your argument-that’s-not-an-argument?
Mark asked “Can you give a serious scientific argument?”
-cvj
Clifford,
No, I’m not “condemning an entire field’s scientific efforts”, I’m accurately describing the current state of efforts to use “string theory backgrounds” to explain anything about particle physics.
You, on the other hand, are behaving like a child. Grow up.
And there, ladies and gentlemen, you see the type of rigourous scientific argumentation Peter Woit uses to condemn an entire field’s scientific efforts.
See my point (3) in comment 7.
-cvj
Mark,
At one point I engaged in a detailed discussion about what people claim is the most robust “prediction” about supersymmetry breaking, that of gaugino mass ratios, you can find it somewhere on Cosmic Variance I think. The bottom line is that there are supersymmetry breaking scenarios that give you pretty much any mass ratios you want. Sure, if you pick specific backgrounds that people have studied, some come with constraints on the gaugino mass ratios when you make various reasonable assumptions. I understand that some people hope that the LHC will
1. see gauginos
2. find that the mass ratios fit the pattern of a certain class of backgrounds.
I just think that, while this is the best case scenario for the string theory unification program, it’s still highly unlikely. There’s zero evidence in anything we know about particle physics for this at the moment, and there’s nothing aesthetically or otherwise compelling about these backgrounds. Quite the opposite, they don’t explain a single thing about standard model physics, and these models are both spectacularly ugly and unpredictive.
Absent any evidence for this in anything we know about, hoping to see it at the LHC is not based on science, but on wishful thinking. It’s right up there with, say, large extra dimensions of exactly the right size so that the Tevatron sees no indication of them, but they show up at the LHC. This is not logically impossible, but there’s not a shred of evidence for it now, and it wouldn’t explain anything we do see.
It’s my impression that most particle physicists believe that extra dimensions are highly unlikely to show up at LHC scales, precisely because there’s no evidence for this, and no scientific reason to expect it to happen. I don’t think the supersymmetry pattern business is much different.
Although I work in an unrelated field, I have come up with some challenging and contraversial ideas about string theory that are going to upset those in the mainstream.
Unfortunately I have to go out for a bit, so I can’t discuss my ideas right now, but I just wanted you all to know that I know that you are wrong.
Peter, in your blog you said:
“I think the great hope of some string theorists is that the LHC will see not only supersymmetry, but a pattern of supersymmetry breaking that corresponds distinctively to a certain kind of string background. Based on this they might then be able to make real testable predictions. This seems to me to be nothing but wishful thinking, we’ll find out in the next few years.”
I don’t see how you can call “wishful thinking” a serious argument. Do you think that it would be impossible in principle to indentify the pattern of SUSY breaking? Can you give a serious scientific argument?
Thank you!
I learnt about zeta function regularisation in string theory from David Gross many years ago and I must say that after only a little thought I shared Carl’s reaction.
Yes Clifford, nothing new here. You continue to refuse to actually address the argument I am making.
The only thing I’m trying to poison is the less than honest hype that has surrounded string theory for far too long. You’re free to get on with your work on string theory, I’m not interfering with that in any way. You’re also free to continue to spend your time writing blog entries promoting overhyped advertising for the subject such as the Physics World article and attacking me as “ill-informed”. When you do this, I’ll continue to spend some time providing the other side of this story.
Partly due to my book and Lee Smolin’s, partly due to the ever-more-obvious failure of string theory unification represented by books like Susskind’s promoting obvious pseudo-science, I think people’s view of string theory is much more realistic these days. It’s unfortunate that, instead of adopting a realistic view of what has worked and what hasn’t, some string theorists feel that the thing to do now is to just increase the hype level. As long as they are doing this, I’ll spend some time poisoning such efforts.
Nothing new here to see.
I refer you again to the last part of my earlier comment:
-cvj
Clifford,
I nowhere have ever claimed to have a “proof” that string theory can’t make contact with experiment. Without an actual definition of what “string theory” is, you can’t “prove” anything about “string theory” as such. One thing the slides contain is a discussion of all the various well-known claims for such a contact, and an explanation of the problems inherent in all such claims. The general reasons why such attempts to connect string-based unification to experiment don’t work are examined, and I think this provides a compelling argument that string-based unification is a failed idea. For nearly 25 years many, many people have worked very hard at it, and what they have learned has made clear what the fundamental problems are that keeps the idea from getting anywhere. I’ve made a serious scientific argument about why this idea can’t work (no, not provided a “proof” that it can’t). I don’t believe there is a serious scientific argument on the other side, giving some sort of plausibility argument about how these problems will be overcome.
This is the problem with your “too soon to tell” argument. 23 years of utter failure and increasing knowledge about how serious the problems are with getting unification out of a 10/11d theory just can’t be waved away this easily. The Cartwright-Frigg article explain how a scientific research program does not need to be immediately testable, but does need to be “progressive”, making progress towards such testability. The problem with string theory is that it is going in the other direction, making progress towards showing such testability is impossible.
Alejandro asks:
It says so because that was when Witten made his announcement. The papers you refer to are about field theory not string theory. Note the title that you quote, for example, which gives a clue to the subject matter of the paper.
Carl: First of all it is 1+2+3+4+….. Second of all….. oh dear, never mind.
-cvj
I do rather ruthlessly delete comments submitted to my blog that are ill-informed and just add to the noise level, especially the large number from people who think that my blog is a good place to promote their personal “alternative” views about physics. While I rarely if ever delete comments defending string theory, I delete a very large number of comments that attack string theory in an ill-informed way. A good example would be one like Carl’s above. The problem with string theory is not that it uses zeta-function regularization or extra dimensions.
By the way, now i read again the article… why does it says that the important work on dualities implying M-theory was presented in string95? I think to remember that most of the work was presented in Le Sorbonne in 1994, under the tittle Electric magnetic duality in four-dimensional gauge theories., simultaneous to the publication of hep-th/9407087 and with some slides related to hep-th/9408074. I was on the understanding that it was this presentation -read, you can say, in the same rooms used by Claude Levy-Strauss in 1968 – which was named as the “second superstring revolution”. Witten contribution in Strings 95 is hep-th/9507121, isn’t it?
Peter:
If you recall, I read those slides, and commented on them. How can this be interpreted as ignoring them? There’s nothing of technical substance there that would constitute your claimed proof that string theory cannot make contact with experiment. What you have is your version of a plausibility argument – not a proof of anything. Again, this is all in the comments of earlier discussions.
Best,
-cvj
Regarding Clifford’s blog and the moderation of comments.
I used to read Woit’s blog but quit a year ago or so, partly after seeing them primarily used to support book sales (and mostly lacking other content) and partly in frustration over how he treated comments. His treatment of comments is far more draconian than Clifford’s.
It’s not about whether or not you believe in string theory. Personally, I think string theory is garbage. I studied QFT back in the early 80s. Eventually I wondered where the field had gone, so I picked up a text book on string theory and started reading it. Within minutes I was laughing at the mathematical errors and lack of physical intuition. 1 + 4 + 9 + 25 + … is simply not equal to -1/12 (or whatever they get). Spacetime does not have 11 dimensions, it has 3+1.
The fact that Clifford has failed to read the Woit and Smolin books, but still feels competent to comment on their content is a travesty. Clifford can intelligently comment on what he’s read, no more and no less, and what he’s read consists of commentary on these books, not the books themselves. One might as well take the stance that a physicist who has read commentary about a string theory book, but not read the book, can make intelligent comments about the content of the book.
But no, Clifford doesn’t moderate in a vicious manner. Woit’s comments hit the moderation queue probably because they had too many links in them.
Clifford,
I’ll let people read exchanges between us here and elsewhere and decide for themselves which of us is best described as using “schoolyard tactics”.
The book is nearly 300 pages long and the result of a very serious and extensive effort to carefully write down my arguments on this topic. It’s a very different sort of thing than quickly written entries for blog comments section. There are many, many aspects of my arguments that are in the book, but not in blog comment exchanges. Both Lee and I have repeatedly tried to explain to you that if you want to engage seriously with the arguments of someone who has taken a lot of trouble to get them down coherently in one place, that’s the place you have to go to find out what they are. Your refusal to do so speaks for itself.
Besides the book, for something a bit more technical there are the slides of my talks earlier this year at physics departments in Rome and Pisa which I’ve repeatedly pointed you to. Again, that’s a second place you can find some of my arguments carefully laid out, and you’ve chosen to ignore them in that form also.
Hi Peter – the evidence is in all the blog discussions I’ve pointed to that everyone’s free to read. They can watch you stumbling around to make a coherent scientific argument when pressed for one (and trying several amusing schoolyard tactics to distract readers when you fail) to their heart’s content, and they can read myself and others addressing your key points head on over the course of the last two years or more. Pretending that those discussions don’t exist won’t help. They are part of the public record.
For the record, I denounced your arguments and claims – not your book, which I’d never read. However, I think I recall someone asking you in an earlier thread whether your book makes different claims than you’ve made on blogs and I don’t recall you saying there was a difference. My memory is possibly faulty on that, so feel free to come out and say that you’ve been saying two different things entirely.
I’m not trying to insult you about being uninformed. I’m really not. It is simply a statement of fact supported by the evidence. There’s lots of things I’m uninformed about and I don’t mind people stating it. However, I don’t claim to be an expert on those things and publicly condemn out of hand other people’s work on them, even writing books doing that, while at the same time not being able to support my claims.
Anyway, this is a tired circle we’re about to engage on and I’ll opt out. I’ll simply invite the reader who is interested to follow the nice trail you’ve left in all the posts I’ve pointed to, where you demonstrate your confusion between not liking something on the one hand, and having something scientific to prove on the other.
I’m glad to hear your work is going well. I wish you all the best. Perhaps you should consider letting others get on with their work too, rather than trying to poison people against it.
Best wishes,
-cvj
Clifford,
You don’t know what my arguments are since you refuse to read them. As to why I thought you had read them when you hadn’t, it wasn’t because you showed any signs of knowing what my arguments actually were, it was that it never occurred to me as a possibility that an academic would even consider the idea of writing long denunciations of a book they had never bothered to read.
As for your insults about how uninformed I am, don’t understand what I’m talking about, am just intent on deceiving the public, etc., they’re really tired. You have no idea what you are talking about since you refuse to read what I write, but think that this kind of insult and put-down is an appropriate response.
Thanks for your concern about my own research. I do spend a lot of time on it, and am making slow progress.
Hi Peter,
1) The issue of whether I’ve read the books or not is -as you know- a red herring. We’ve been discussing in detail the content of your arguments together for almost three years now. I don’t need to read the books for that. I’ve been talking about the content of your arguments and debating them with you. It’s an obvious distraction to continue on about that issue. (Recall that my discussion of your arguments with you was so convincing for two years that you in fact went as far as to make up the story and publicly announce that I’d reviewed your book for the publisher CUP, only to have to withdraw your claim later. So you’re trying to have your cake and eat it.)
2) This is a scientific discussion. When asked in many places to defend your scientific claims with a scientific argument, you failed miserably to do that, as anyone can read in the discussion threads that I’ve pointed to in the post above. Hiding the lack of scientific content of your arguments in lots of fluffy stuff in a book is not how we do scientific discussion in physics.
3) You are entitled to your opinion and gut feeling about the rightness or wrongness of what we are doing (based as they are on an oft-demonstrated lack of understanding about most of what is going on at a technical level, but that’s ok), but dressing that opinion up as scientific fact and deceiving the general public and the yes-men who read your blog (I certainly don’t!) into thinking it is scientific fact is not a good thing to do.
4) The other reason I (and many others) don’t read your blog is because the whole one-note song is tiresome and boring. You just sit around waiting for negative things to say about string theory. You can’t help yourself but ignore anything positive and jump to find the most negative conclusions that fit your already firmly formed view. Most of us just want to stay neutral about the whole thing -pragmatic. We want to get on with doing the research (or letting others who know what they are talking about get on with it) and let the results determine our opinions, rather than decide before hand. Open-mindedness vs prejudice, you see.
5) While I’m on the topic…. rather than sitting around waiting to pounce on everything everybody says about strings, wouldn’t it be a whole lot more productive to do some research on your own approach, and produce an alternative that does a better job?
6) These remarks (points 1-6) have all been said so many times, by so many.
Thanks,
-cvj
Sorry Peter. I did not see the spam filter doing this. I’ll have a look. If I find it, it will appear with the earlier timestamp and hence above your comment #4, and so I will change the timestamp to have it appear below, so as not to confuse.
Anyhow, you seem to have succeeded now.
Cheers,
-cvj
Clifford,
My repeated attempts to post a comment about this here have been blocked, presumably by your spam-filter. If you can unblock one of them, that would be helpful.
There was an extensive discussion of this article at my blog two weeks ago, see
http://www.math.columbia.edu/~woit/wordpress/?p=593
This included an extensive exchange with the author of the piece. Anyone reading the Physics World piece should be aware that it contains quite a few inaccuracies and large amounts of hype, together with some information that is simply unarguably out and out false (no, Witten did not win a Fields medal for his work on Calabi-Yau compactifications of string theory). The same issue of Physics World contains several other shorter pieces about string theory, discussed here:
http://www.math.columbia.edu/~woit/wordpress/?p=599
These include a piece by theorist Fred Goldhaber describing currently popular work on the string theory landscape as “antiscience”, and a piece by philosopher’s Cartwright and Frigg that explains why just repeating “it’s too soon to tell” in response to criticisms of a research program is not enough.
As for whether Lee Smolin and I have written uninformed, sensational books poisoned by prejudice, note that Clifford is famous for steadfastly refusing to read these books (or my blog, it appears, since the “Stringscape” article is new to him), making his views on our arguments well, uninformed and poisoned by prejudice, I would say…
[originally had timestamp 11:22am; see previous two comments- cvj]
That is a beautifully written article, the kind of article I’d enjoy reading if I wanted to get a glimpse of a subject far from my expertise (rather than just forming an opinion on it). I’d definitely be bored reading articles about what some micro-biologist or economist think about their colleagues, carefully avoiding any mention of micro-biology or economics. I am glad to see some movement away from that tiresome genre.
Hi Alejandro: N is the inverse string coupling, so the nature of the corrections to the strict large N limit are accessible by studying corrections to the leading string results. Also, the supersymmetry is not really relevant, it seems, for lots of things being studied – the string theories are not supersymmetric in the regimes being studied. Please read the post I pointed to for why a lot of these details may be less important than they might seem. The upshot is that these are not QCD, but may give us access to many physical properties of value that are shared by QCD.
-cvj
My problem with large N QCD is that real world is not large N. Furthermore, the only possibility I have seen to stablish some supersymmetry play at the level of hadrons works uniquely for three generations and SU(3) color, where a pair of quarks have the same color charge than an antiquark and you can try quark/diquark susy.