Every year the people running SPIRES put together a list of the most heavily cited papers in their database. I’ve discussed here in the past the listings for 2003, 2004 and 2005. Up until 2003 these appeared with a discussion by Michael Peskin of many of the papers on the list and their significance, but he hasn’t done this for the past couple years. This year, instead of waiting for the SLAC people to put together the list, I decided to generate one myself. I’m not enough of an expert with SPIRES to get it to just give me the list for 2006, but it was an interesting exercise to go through the lists generated by various searches just using their “topcite 50+, topcite 100+, etc…” feature, together with restrictions on dates. I think I was able to compile a complete list of papers with 150 or more citations, and post-1990 papers with 100-150. I was just looking at papers in particle theory (hep-th, hep-ph, hep-lat), not experimental (hep-ex) papers or astrophysics (astro-ph) papers, and was not counting survey articles. I’ve put the full list on a separate web-page, Most Heavily Cited Theoretical Particle Physics Papers 2006.
There are of course lots of caveats about any conclusions drawn from counting citations, but these numbers do give some solid data about what is going on these days in particle theory research. Two topics from nearly a decade ago continue to dominate these citation counts: AdS/CFT and brane-world models. By far the most heavily cited paper is the original 1997 one by Maldacena (546 citations), and the number of such citations has actually increased significantly over the number in 2004 (451) and 2005 (436). Research into AdS/CFT heavily dominates current particle theory research, but, remarkably, this research has not led to any recent heavily-cited papers on the subject. After a flurry of activity in 1998-2000, the only 21st century paper on the topic with over 100 citations in 2006 is the 2002 paper on pp-wave backgrounds by Berenstein et. al.
Overall, the list provides a very depressing view of the first six years of 21st century theoretical particle physics, with only eight post-2000 papers getting over 100 citations. These break up neatly into 4 hep-th string theory papers and 4 hep-ph phenomenology papers. Besides the 2002 pp-wave paper (hep-th/0202021) the other three string theory papers are all about the landscape, with the KKLT paper (hep-th/0301240) getting by far the most citations (238), followed by hep-th/0105097 (Giddings, Kachru, Polchinski) with 150, and Susskind’s hep-th/0302219 (“The Anthropic landscape of string theory”) with 109.
The heavily cited phenomenology papers are mostly compilations of theoretical fits to experimental data: hep-ph/0201195 (parton distributions, 193 citations), hep-ph/0405172 (neutrino oscillations, 133 citations), hep-ph/0406184 (CKM matrix, 118) and hep-ph/0506083 (neutrino mass matrix, 103 citations).
While getting this list together, I also accumulated some other data, including lists of recent papers with citation counts in the range of 50-100, and will try and put this together and write about it sometime soon.
Some other data one might want to take a look at is the arXiv monthly count of submissions (I found out about this from a posting at physicsforums). It shows the number of HEP submissions growing until about 2002, more or less flat since then, although each of the last two years have shown slight declines.
I’ll avoid the temptation to make extensive editorial comment on the meaning of these numbers, but I find it hard to believe that anyone could claim that they reflect a healthy field. The domination of non-phenomenological particle theory research by landscape studies is especially disturbing.
Peter said “… a posting at physicsforums). It shows the number of HEP submissions growing until about 2002, more or less flat since then, although each of the last two years have shown slight declines. …”.
2002 was the year that the Cornell arXiv began (or greatly expanded) its blacklisting actvity. A 14 October 2002 e-mail message from register-query@arXiv.org (not addressed to me, but it was forwarded to me which is how I know the quote is accurate) referred to:
“… a large pool here – typically flagged by reader complaints …”.
Without regard to whether or not any particular person (me or any other) should have been blacklisted,
it appears that 2002 marked the establishment of a policy of using “reader complaints” as a basis for rejection of submissions from people in the “large pool”.
I am not surprised that the establishment of such a policy coincides with a flattening of the number of submissions, followed by slight declines.
I (for the record I am not disinterested in such matters) feel that this does indeed not “reflect a healthy field”.
Tony Smith
http://www.valdostamuseum.org/hamsmith/
As far as I know, which is very little, there are a few “referees” working ad-honorem for the arXiv. Submissions are not evaluated in detail but, rather, by their abstracts. The number of preprints actually rejected is allegedly extremely low, and consists of obviously nonsensical submissions. I don’t think those very few rejections should have any impact on the global statistics of a given research field.
Hi Peter,
“Overall, the list provides a very depressing view of the first six years of 21st century theoretical particle physics, with only eight post-2000 papers getting over 100 citations.”
I’m not sure how you did the search but you somehow missed all these papers with over 100 citations:
hep-th/0011089, hep-th/0109152, hep-th/0308089,
hep-th/0308055, hep-th/0309187, hep-th/0404257,
hep-th/0404116, hep-th/0403047, hep-th/0312171,
hep-th/0301006, hep-th/0301006, etc.
So, it’s not so depressing 🙂
“…with only eight post-2000 papers getting over 100 citations” during the year 2006.
For example, the famous paper by Maldacena got 546 citations in 2006, and 436 in 2005.
student,
I was talking about number of citations/year, specifically the number in 2006. For instance, the first paper you mention has more than 100 citations, but over more than six years. It looks like during 2006 it had only 7 citations.
Peter: When did you compile your data from Spires? — There was an (unannounced) bug with their database search routines for most of Wed 17 Jan which caused large numbers of articles to be unfindable using the standard search interface… As “student” points out:
“I’m not sure how you did the search but you somehow missed all these papers with over 100 citations:
hep-th/0011089, hep-th/0109152, hep-th/0308089,
hep-th/0308055, hep-th/0309187, hep-th/0404257,
hep-th/0404116, hep-th/0403047, hep-th/0312171,
hep-th/0301006, hep-th/0301006, etc.”
Spires now seems to be functioning normally, and it would be worth double-checking your searches.
Matt,
I did the searches the evening of the 17th, and a few this morning (the 18th). Earlier in the day I had been trying various things on SPIRES and once or twice noticed some anomalous behavior. But while I was doing the searches, SPIRES seemed to be fine, and all the numbers I was getting appeared to be consistent. In particular I was going through the 2005 topcites list as a starting point, and the 2005-2006 numbers tend to be similar with a couple interesting exceptions (interest in pentaquarks dropped like a stone in 2006…).
Again, this is 100 citations/year, not total citations. If anyone can point to a paper that isn’t on my list that got over 100 citations, please let me know.
Peter, why do you think lots of recent papers should have over 100 citations in a year in a healthy field? It’s not at all clear to me that this is a measure of the health of a field. One could argue the opposite, that it’s a sign of a healthy diversity of research topics.
Also, it seems to be a stretch to say that non-phenomenological theory is “dominated” by landscape studies. A quick look at the past week of hep-th shows about 4 or 5 landscape-related papers (things like moduli stabilization) out of 66 total papers. That is hardly “domination.”
Dont’ know whether this link has shown up already, but here goes:
Interview with Lee Smolin in the IEEE Spectrum Magazine:
http://www.spectrum.ieee.org/jan07/4812
Nothing unusual.
anonymous,
Particle theory has always been a field where promising new ideas quickly attract a lot of attention, with lots of people soon writing papers trying to exploit the new idea and see what they can do with it. I just don’t see any evidence for the claim that what is going on here is that there are as many promising new ideas as there used to be, but people are not pursuing them, rebelling against particle theory’s traditonal trendiness and going for diversity. It seems to me that the evidence is overwhelming that the post 2000 period for particle theory has been characterized by an historically unprecedented dearth of new ideas.
The dominance of landscape studies that I was writing about is not an absolute dominance in terms of numbers of papers being written, but a dominance in the area of new ideas that the community has chosen to pursue. The data about which recent papers are getting most heavily cited is unambiguous.
To put it crudely and bluntly: sure, lots of people are not working on the landscape, far more are working on AdS/CFT or on other topics. But they’re not writing papers that many other people think contain promising ideas worth pursuing. The landscape people are the only ones recently to be writing papers that inspire many others to follow them and work on the same thing.
anonymous, here is something to help you decide about the health issue that concerns you
in year 2000 there were twenty-one recent string papers (papers that appeared in the past five years 1996-2000) which got 100+ cites in 2000
in year 2006 by Peter’s list there were three recent string papers (papers that appeared in the past five years 2002-2006) which got 100+ cites in 2006
we are talking healthy field and comparing. You ask:
Peter, why do you think lots of recent papers should have over 100 citations in a year in a healthy field? It’s not at all clear to me that this is a measure of the health of a field. One could argue the opposite, that it’s a sign of a healthy diversity of research topics…
Maybe it will help make it more clear to you if you compare 2000 with 2006 and see if there is a more healthy diversity of research topics now in 2006 than there was in 2000, since the cite numbers are so much less.
I think if you go back and look at the titles and abstracts of some of those 21 papers you will decide not. But here is the 2000 list if you want to try.
http://www.slac.stanford.edu/library/topcites/top40.2000.shtml
It’s unfortunate that we don’t have a good database of complete particle theory citation counts stretching back to the 40s or earlier; I strongly doubt that it’s always the case in any given year that there are lots of good new ideas that get over 100 citations in one year, within a year or a few of their publication.
The “100 citations” mark is a bit high to extract meaningful information from, I think. Let’s look at one recent paper that “many other people think contain[s] promising ideas worth pursuing”: Intriligator, Seiberg, and Shih, hep-th/0602239, already has 52 citations. Surely by any reasonable standard this is a paper that has inspired other people to follow up on it. Other recent trends, just off the top of my head, include the study of energy loss in quark-gluon plasma, integrability in N=4 SYM, and trying to understand general constraints on infrared modifications of gravity. There are plenty of papers on all of these topics, but not necessarily one extremely highly-cited and very recent paper that kicked off the trend. They don’t meet your criteria for what is trendy, but I think most people in the field would say they are healthy trends.
For that matter, hep-ph/0507005, “Bootstrapping multi-parton loop amplitudes in QCD” by Bern, Dixon, and Kosower, has 57 citations. That might not match your standards, but 57 citations in a year and a half for a highly technical paper is impressive, and I don’t think anyone can argue that this is not good and highly relevant physics.
Who, your comment appeared as I was writing mine: I don’t think it’s fair to expect any given year to match the explosion of work that followed AdS/CFT and the beginning of extra-dimensional model building. The fact that a few major new ideas appeared at that time doesn’t mean that more recent new ideas are completely useless. For that matter, many of the most important papers in the history of theoretical physics failed to provoke the sort of flurry of new papers that AdS/CFT did. AdS/CFT is a sociological anomaly.
anonymous,
Personally I happen to think the various work you quote is among the best work going on in particle physics, but it’s not very promising that it will ever lead to important progress in the field. That’s just my opinion, and you’re welcome to dismiss it as such, and instead claim that in your opinion the best current work in particle theory is every bit as promising as that of any other period.
But the numbers I’m discussing here are not matters of opinion but solid facts about exactly how particle theorists are voting with their feet about what’s an idea worth working on and what isn’t. If you have facts to back up your claims, let’s hear them. SPIRES data does go quite a ways back, I just noticed that they now have “topcites” lists going all the way back to 1974. If you look at any of the lists from before the last few years you’ll see large numbers of recent papers amongst the most heavily cited ones. For something really dramatic, take a look at the first one, 1974. The overall number of papers was much lower, with the most heavily cited papers getting 150-200 citations, unlike the 3-500 we see now, but virtually every paper on that 1974 topcite list is a recent one from the previous six years.
1974 was an unusual year, just after the birth of the standard model, but the data for more than 30 years is there. If you can find some evidence in it to support your claims, lets hear it.
anonymous,
If you think 2000 is an unfair year to pick, pick any other one. For instance pick 1997, right before AdS/CFT. Of the 6 most heavily cited theory papers, guess how many were written during the previous 4 years? ALL of them.
It seems that the paper by Minahan and Zarembo hep-th/0212208 has around 100 citations in 2006.
Graduate Student,
My SPIRES search gave 94 citations for the Minahan-Zarembo paper in 2006.
Overall, the list provides a very depressing view of the first six years of 21st century theoretical particle physics,
That’s probably because you’ve excluded astro-ph?
Anyway, looking at your list I should have cited at least half of the papers you listed at one point or the other, not sure if I actually did though. E.g. the PYTHIA, CTEQ, global neutrino fits etc, it’s fairly easy to accidentally cite a paper referring to an older version, and those guys usually don’t complain. Its still puzzling me why journals have no policy on what has to be cited and what hasn’t. Admittedly, I think it would be as important to have a policy on what papers are not to be cited. There are just too many people who cite papers that have only a vague connection to their work, or because they know the authors, or because the author is one of those who will sent you an email saying ‘I want to draw your attention to MY VERY INTERSTING PAPER… ‘
Interesting post, thanks.
Best,
B.
Peter,
your measure seems quite arbitrary; for example, some new ideas generate a lot of new papers since many “relatively simple” things can be worked out in the beginning (like what has happened with AdS/CFT), other ideas take longer to generate new papers since the ideas can involve things which at least some people have a harder time understanding (like with the geometric Langlands program).
So,
(1)how would you quantify your claim, that “but I find it hard to believe that anyone could claim that they [those numbers ]reflect a healthy field.?
(2)Have you compared with another field of research which you consider as being “healthy”?
(3) Have you tried to do the same “statistical” analysis in some sub-field of mathematics, for example? And what would then be your conclusion?
-Kasper
Bee,
Sure, astrophysics and cosmology are quite healthy subjects, unlike particle physics. While I was making up this list, I was looking at papers that appeared in astro-ph that had large numbers of citations to see if any had much relevance to particle physics. The only candidates were papers about the vacuum energy and things like “phantom energy”. It’s certainly true that astrophysical observations of a CC pose a serious challenge to fundamental particle physics, but unfortunately I don’t think anyone has a promising idea about what to do about his.
Kasper,
I very explicitly quantified my claim: a healthy field is one that is generating significant numbers of promising new ideas, and the best objective standard I can think of is to look at what work people are citing in their current work, and how much of it is recent. If you have a better objective standard, let’s hear it and let’s see some objective evidence that particle theory is doing well these days.
Your conjecture seems to be that maybe the current situation is different than the one of the past in that now there is plenty of progress and promising ideas out there, but, unlike in the past, few people are working on these ideas. I don’t believe this, and don’t see any evidence for it. If you have some evidence that this is what is going on, that this explains the difference in numbers between now and the past, let’s see the evidence.
I’m a great fan of the recent work on geometric Langlands, but I don’t think large numbers of people are going to work on it anytime soon. This is not because it is difficult (which it is), but because it doesn’t appear to show any obvious promise as an idea about solving particle physics problems.
If you want an example of a healthy field, as Bee suggests look at astrophysics. I don’t have time to generate numbers, but if you look at the 2005 SPIRES topcites list, you’ll see that most of the astrophysics papers listed there are recent ones.
I haven’t tried to do the same exercise in mathematics, it would be complicated because there are lots of sub-fields, lots of overlap of sub-fields, and much smaller communities working on the same problems. Mathematics definitely has more and less healthy sub-fields; one could probably identify some that are pretty moribund, with few promising recent ideas. The subfields of math that dominate major research universities appear to be quite healthy though, with for instance the solution to the Poincare conjecture and Fermat’s Last Theorem in recent years. I know of no reason to suspect that you would see a big difference in the fraction of heavily cited papers that are recent now versus in the past in most subfields of math.
I recently read that Steven Weinberg considered the most important task ahead in theory research was to understand better the various effective field theories in hadron physics. He felt deep insights – and perhaps important new physics – lay within these structures.
I’m wondering if any theorist(s) are paying much attention to his views (sufficiently more than to AdS/CFT research)?
Michael
Oh, and by the way, I was curious about another issue:
Besides string theory research, were there any other theory paper(s) [hep-th, hep-ph, hep-lat, or (also) math-ph] that generated interest within the field?
I think the era of effective field theories is beginning to dawn on the research horizon. Any comments to this view?
Michael
Michael,
Weinberg’s views about the importance of effective field theories are the dominant paradigm in particle physics, and this has been true for 30 years or so. There is no danger that these views (or others of Weinberg) are being ignored.
Hi:
Actually, if you look for *why* the so-called landscape papers you mention are well cited, the reason is not much to do with what you regularly bash as “landscape studies.”
A few of the citations are from papers about anthropics or the multiverse.
The vast majority are from papers that try to build realistic models: that is papers that are trying to achieve realistic inflation, or particle physics, or both, in a concrete string model. While you can call this “landscape studies,” most people would probably call it model building. One can argue about whether one should try to build models of realistic physics all the way from the planck scale down using string theory, but this is a pretty traditional goal of particle physics (starting with GUTs where speculations about ridiculous energy scales became fashionable). Arguably almost all papers on SUSY are motivated by this goal also (with unification being one of the pillars that drives SUSY model building).
So Minahan and Zarembo are almost there. Nevertheless I think this is an active area of research in hep-th. I don’t know if you consider this area to be part of string theory (via AdS/CFT) or QFT…
If you think arXiv rejects papers which are obviously nonsense, search for papers by Mueckenheim. I’ve spotted a few others, but can’t remember right now.
wow,
One of the papers is Susskind’s anthropic manifesto. Sure, the citations of the other two often come from “landscape” model-building that doesn’t necessarily involve anthropics. But I still think this kind of model-building is highly problematic. The models are inherently complicated and ugly, unmotivated by any physical evidence that points to them, and seem able to reproduce virtually any extension of the SM that one wants, leading to a real question about whether this kind of model-building is normal, falsifiable science at all.
“There are just too many people who cite papers that have only a vague connection to their work, or because they know the authors, or because the author is one of those who will sent you an email saying ‘I want to draw your attention to MY VERY INTERSTING PAPER… ‘”
I don’t see anything particularly harmful in this. I’m sure you know how irritating it is when people who ought to cite you fail to do so, and I just don’t want to be one of *those* people who only cite the works of famous people. Look at the cites for Witten’s Geometric Langlands papers: most of them just seem to think that having that name on their paper will miraculously render it more likely to be published. That is pathetic, but, again, what harm does it do? There is a lot of talk these days about how there are too many bad papers on the arxiv. By people whose papers are, of course, uniformly excellent.
Peter,
If this is the case – that Weinberg’s view(s) have remained, and continue to remain, the most important paradigm in particle theory – surely his research program is worth persuing for young grad students and postdocs. Why spend so much of ones efforts on ‘string theory’ and such when (arguably) the most important research direction is staring us in the face? Am I [simply?] missing some information / insight into the field or does such a view seem quite obvious and relevant; I still don’t know why SO MANY of the brightest in the field spend time with strings and other highly speculative ideas when EFT may be the most important direction of research for the current generation (to perhaps the next or beyond) of physicists.
Any idea, feedback, etc?
Also, would you happen to know where CP violation studies currently stand? Is CP violation studies directly related to EFT research?
Michael
Peter, I am somewhat puzzled that you did not consider theoretical condensed matter physics papers. After all, they are not only an important part of theoretical physics, but they have for a long time been influenced
and have influenced particle theory and quantum and conformal field theory.
David,
One reason for this is that condensed matter theory papers aren’t in SPIRES, but more importantly, I just don’t know very much about the subject, which seems to be a good reason for me not to write about it….
Michael,
Most “string theory” papers ARE effective field theory papers. Effective field theory is an extremely general idea which almost everyone is using. The problem in this field is that nobody has a good idea WHICH effective field theory will get us beyond the standard model (which most people believe is an effective field theory itself).
Daved Deutsch is joining the debate as well regarding string theory. In the December 9 issue of New Scientist he comments on string theory as follows:
“I think it’s unlikely that a research programme of that kind can work. Even if you found the right mathematical object, you probably wouldn’t even recognise it because you wouldn’t know how it corresponds with the world. For example, if someone had invented quantum theory purely as a mathematical model, how would they ever guess that its multi-valued variables correspond with quantities that we measure with single values? After all, it assigns multiple values to observable quantities simultaneously. I would warn against expecting the answer to come from a new mathematical model. It should be the other way around: first find what you think might be the solution to a problem, then express it as a mathematical model, then test it.”
About the Deutsch quote. I haven’t looked at the original article, but if he’s really refering to string theory, I don’t think his argument makes any sense. To defend string theorists, they are not working with “purely mathematical models”, with no idea how to connect them to quantities we can measure. Their problem is quite different: when they do try and use string theories to model a unified theory of gravity and particle physics, the simplest forms of string theory are inconsistent with what we observe, and making the theory more complicated to get around this makes the theory consistent with almost anything and thus unpredictive.
Michael wrote: “I recently read that Steven Weinberg considered the most important task ahead in theory research was to understand better the various effective field theories in hadron physics. He felt deep insights – and perhaps important new physics – lay within these structures.”
Do you have a link or a reference for this? I feel like there’s a miscommunication between you and Peter in this discussion, because I don’t think Weinberg would say that the most important task ahead is for people to understand “effective field theory” in the general sense Peter is interpreting it as. Pretty much everyone in the field understands that. I expect Weinberg means particular effective field theories (hence, “in hadron physics”), probably formalisms like SCET.
Peter,
I know that this is not your meaning, but
to many people the number of times a
paper is cited is the main indicator of how
valuable the work is. I would not dispute
that the number of citations is a parameter
which has some use, but the emotional
reliance on this number is, in itself, unhealthy.
Are we to evaluate ourselves the same way
chairs, deans and provosts evaluate us?
I was at a large string theory conference
some years ago and one speaker who had
been giving many talks “challenged” the
audience with the question, “What will
be the next string theory paper to garner
500 citations?”. Everyone seemed highly
animated and thrilled by this disgusting,
prurient line of thought. I mentioned to a
young string theorist, who had been very
excited by this question, that the number
of citations is much less significant than
an experimental prediction. He replied
that if this were to happen in string theory,
he would switch to pure mathematics. I
interpret this to mean he was actually
indimidated by the thought of confronting
real science.
I realize that you are trying to make a
particular point with SPIRES and the
time-dependence of citations. Part of the
reason for the phenomenon you mention
is that people to believe that highly-cited
papers must be good, so those are the
papers which garner more citations. This
is symptom of the short-term scholarship
in our field.
Speaking of citations, would you believe a spill-over of eternal inflation and the multiverse into evolutionary biology? See q-bio.PE/0701023:
Nobody presently knows what future good physics is, and citations allow to do a democratic pool. It will be interesting to wait some decades and measure the correlation between good physics and highly cited physics. Probably the result will be what Feynman described as:
“Nobody was permitted to see the Emperor of China, and the question was, What is the length of the Emperor of China’s nose? To find out, you go all over the country asking people what they think the length of the Emperor of China’s nose is, and you average it. And that would be very “accurate” because you have averaged so many people. But it’s no way to find anything out; when you have a very wide range of people who contribute without looking carefully at it, you don’t improve your knowledge of the situation by averaging.”
M, it is more democratic to take a consensus by averaging guesses than by imposing a particular person’s guess. At least this process has the benefit of eliminating all extreme guesses, which are crazy enough to have a chance of being correct.
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Q, ultimately some experimentalist will decide for everybody, and many top-cited papers will end up in the trash. Science is not democracy.
I agree that in the meantime citations might be a good alternative, but without forgetting its limitations, like the one you mention. Quoting Winston Churchill: “democracy is the worst form of government except all the others that have been tried”.
I guess you meant a “demographic poll”? But I agree with you: since nobody knows yet what new physics is going to be, citations reflect what most people in the field is working on, but not necessarily where the good physics is.
Once a paper has a few thousand citations, it will remain in the top cited list for a very long time. If it’s more than 2000, then it will remain there for decades to come, maybe even forever…
Funny thing is, if susy and/or extra dimensions are not seen at the LHC, several papers on either subject will be stuck in the top-cited list in HEP, even though nobody is going to be working on that anymore…
On a related note, there’s not only the list of top-cited papers. I read in the December issue of Physics Today that there are five new books on susy and/or susy phenomenology. I don’t doubt all of them are very good books. I wonder how many good books on susy and its phenomenology are there now in the market. One dozen? Several dozens?
In this respect, I think there are two scenarios for LHC physics, and both look equally ludicrous to me.
In the first scenario susy is observed at the LHC. The idea that the discovery of new particles has not only been predicted, but actually preceded by more than a dozen books about them is definitely preposterous.
Just imagine that between 1946 and 1976 people had been very busy writing large numbers of books about the Upsilon and b physics… does that make sense from a historical perspective? It’d be like a movie played backwards, and equally hilarious 🙂
The second, no less ludicrous, scenario is that susy is not observed at the LHC. Then, what are historians of physics going to make of the last 30 year period? What are they going to have to say about an entire community working for decades on a field, to the extreme of writing several dozen books about it, when actually there will be no hint of the relevance of that field to nature? Again, it’d be a very funny situation…
I’d like to make clear that it certainly is not my opinion that number of citations indicates a paper’s value. These citation numbers are interesting purely for providing an objective measure of what topics particle theorists are working on, and what past ideas people have decided are worth pursuing and are using to write new papers. It’s no secret that I think there’s a serious problem with the choices that are being made and would like to see very different ones….
Regarding the Deutsch quote, I think he may have been trying to make a more general point, since he referred to “a research programme OF THAT KIND”. He apparently thinks string theory is (or at least was) a research program whose modus operendi was to rely heavily on purely mathematical criteria in seeking a “mathematical object” that corresponds with the world. I guess it’s debatable whether the string program fits that description, but this seems to be the KIND of program that Deutsch thinks is unlikely to be successful.
As I understand it, Peter thinks this criticism doesn’t actually apply to the string program. Rather, he says, the string program has been driven by empirical factors, and those factors have falsified the notions arrived at by purely mathematical criteria, so the program can’t be criticized for total reliance on abstract criteria, ignoring empirical facts. He thinks the problem with the string program is in how it has responded to the (what he sees as) empirical falsification, by introducing so much flexibility that it becomes essentially unfalsifiable – thereby rendering it incapable of making any definite predictions.
I think the comments of Deutsch and Woit describe two different problems that can afflict a research program. The string program has probably suffered from both at different times. The fundamental premises underlying the string model, with the extra dimensions, etc., seems (to me) to have been motivated largely by abstract considerations of the kind that Deutsch argues are unlikely to lead to genuine increased understanding of physical phenomena. But I also agree with Peter that, at the present time, the string model seems to have morphed from what once was hoped (and hyped) to be a rigidly unique structure into an almost infinitely flexible curve-fitting formalism (like Ptolmey’s epicycles and deferants) that could be fit to just about any conceivable set of facts.
I suppose, in a way, the two problems are related, i.e., any program devoid of new physical ideas and relying heavily on mathematical criteria, is likely to arrive (at best) at a more sophisticated curve-fitting model.
As an aside, I don’t think there is necessarily anything wrong with devising a better curve-fitting formalism for expressing physical theories. My problem with the string program is that I think a lot of its prominence and funding, etc., has been and still is driven partly by the aura generated by the original hype, which presented string theory as having this marvelously rigid and unique structure, e.g., it ONLY works in this many dimensions, and it REQUIRES this and that, so the impression was given that this program was leading to the unique logically viable structure, which must therefore be true. It isn’t surprising that this prospect got a lot of people (even those with no knowledge or expertise in physics) excited, and the news was on the “front page” of the popular press. Now, decades later, very few people in the field would make those such claims, but the retractions and back-pedaling have much less loudly publicised than the original claims. As a result, I think the string program has continued to benefit from some residual public excitment and hype that, in retrospect, was not justified. So, I think the books of Penrose, Smolin, and Woit are useful in countering some of that effect, and highlighting the fact that the feature of the string program that was originally its main selling point (unique prediction of the logically necessary structure of the universe!) is now very much in doubt.
String theory is definitely Ptolemaic… it is to the standard model as Ptolemy’s cycles and epicycles are to Kepler’s laws and Newton’s theory of gravity. The ultimate theory is supposed to be simpler than the standard model…
I must say I think Deutsch is right on target in the following sense: At this point in the development of string theory, the problem has become, at best, a combination of (1) “what mathematical structures should or must the theory contain” and (2) “what is the right way to set up a correspondence of these structures with observations we can make, or theories that have already tested [ie, the Standard Model]”. The theory has evolved in such a way that it allows enormous latitude for fiddling at both levels, as if its developers imagined that such room for fiddling is what one ought to have in a good theory. In short, the apparent conclusion has become that there is a vast multiplicity of options, any one of which might become “the flavor of the month” as observations come in, ad infinitum.
The seeds for this situation arguably existed in the theory from the start, inasmuch as it began as a stab at understanding the strong interaction, and evolved—based on some formal features of the theory—into an approach to unification and quantum gravity. A clear a priori motivation for the relevance of those formal features to the new context has never been articulated. Similarly, the linking of internal symmetries and spacetime (Poincare) symmetries formally described by supersymmetry has never been understood physically.
In contrast, Einstein’s motivations for replacing the spacetime of Minkowski by a Riemannian spacetime were clear, because he took pains to make them so. He tried very hard to minimize the arbitrariness of his choices. Neither experiment nor mathematical insight (much less mere technical virtuosity) is enough for this. What Einstein had at that time, it seems to me, was a deep insight into what physics was about. An essential aspect of such insight is appreciating the empirical facts of prior theories’ successes, while knowing that these theories cannot be fundamentally correct.
What Einstein had at that time, it seems to me, was a deep insight into what physics was about.
It might be added that the really big breakthroughs of the previous century (SR, GR, QM and renormalization) all involved thinking deeply about observers and observability. I see no reason why QG should be different.
One could look at these results from an optimistic side. Apparently, there was recently no hype that could fool a large part of the community (like the 2004 paper about split supersymmetry, hep-th/0405159, 104 citations in 2005).
But seriously, i really think there is more interesting work going on now than in the last few years, though it does not pass the 100+ trigger. Two examples from my domain: a composite Higgs of hep-ph/0412089, 47 citations in 2006, and a bottom-up approach to AdS/QCD, hep-ph/0501128, 53 citations in 2006.
Good to see that you are making use of the SPIRES database, however, as someone else mentioned, there was an anomaly in our citation data for about 12 hours during the time you were searching. This was due to an error in some new code that we had to release to be able to track citations to the upcoming new arXiv.org ids, as well as tracking other citation forms. For this reason I would be a bit suspect of your data, and I’m sorry that our unfortunate bug caused a problem at the wrong time for your analysis. Beyond that bug there can be some other anomalies, since data mining the database can actually be a bit tricky and it helps to really understand the data and the system.
This year we plan to release the topcites lists on the 31st of January, so your wait will not need to be too long. In the future, if you (or anyone reading this) have some statistical questions like this that we don’t answer via the regular lists, feel free to contact us directly at spires AT slac.stanford.edu and we can often generate such lists and statistics much faster, and more accurately than you can via the web interface. We can’t devote too much time to these things, but we can certainly help when we can. See http://www.slac.stanford.edu/spires/play for examples of this sort of thing.
Best Regards,
Travis
SPIRES Database Manager
Thanks Travis,
I’ve spot-checked the numbers I found earlier, and the ones I checked seem to agree with what SPIRES reports now. Looking foward to seeing your results. I did also gather data on theory papers from the last few years with citations in the range 50-100 in 2006. Before writing about that I guess I’ll wait and see if your numbers are any different than mine.