A random collection of links, on the whole not having anything to do with the holidays:
A Stanford Physics Student in Berkeley is now An American Physics Student in England, and reports from the DAMTP Christmas party, where people were supposed to be wearing “Sci-Fi” costumes, that one physicist came in a black t-shirt with the following printed on the front:
The Anthropic Landscape of String Theory
Leonard Susskind. hep-th/0302019
As far as I can tell, of string theory papers written during the last four years, this is the second most heavily cited (the first is the KKLT one that inspired it). How dare these English people act as if this is some sort of joke?
Raymond Streater’s Lost Causes web-site has always been a wonderful source of anecdotes and opinions. He has a new book coming out any day now from Springer entitled Lost Causes in and Beyond Physics which I’ve just ordered and am looking forward to reading. Streater’s web-site also includes a pretty hilarious commentary on Lubos Motl’s typically absurd review of one of Streater’s earlier books, the deservedly famous PCT, Spin and Statistics and All That, written with Arthur Wightman. I had never realized I was in such good company.
From Streater’s web-site I also found a link to an interesting talk by Guralnick on some of the history he was involved in of work on symmetry breaking in QFT during the sixties which ultimately led to the Glashow-Weinberg-Salam model and what is now known as the Higgs mechanism. The talk tells how leading physicists discouraged work on these ideas as “junk” that wouldn’t lead anywhere and would ensure that one couldn’t get a job. During these years the dominant opinion was that S-matrix theory was the route to future progress, with QFT a dead-end.
Back when I was a physics graduate student I remember every so often picking up a copy of the journal Foundations of Physics and flipping through it, trying to read some of the articles. From what I remember, at the time it struck me as a semi-crackpot phenomenon, mixing a few serious attempts at thinking about foundations with large heaps of nonsense. It seemed clear to me then that serious theorists worked on very different things, trying to understand gauge theories and the Standard Model. A friend of mine who was also a graduate student back in those days recently told me that now the current mainstream literature strikes him as much like that found in the old days in journals like Foundations. I don’t know what this means for physics, but Springer recently announced that Gerard ‘t Hooft (one of the main creators of gauge theory) is taking over as editor-in-chief of the journal. Maybe in times like ours in which there is no experimental guidance, work on foundations should get new emphasis (I think this is one of the points in Lee Smolin’s recent book).
If one wants an overview of recent developments in the interaction of math and physics, one could do a lot worse than read the proposal from various mathematicians and physicists in the Netherlands entitled The Fellowship of Geometry and Quantum Theory (via Klaas Landsman’s web-site).
John Baez’s student Derek Wise has a well-written paper about Cartan connections, and John provides some commentary in his latest This Week’s Finds in Mathematical Physics. I’ve always been fascinated by Cartan connections, since they provide a framework linking very general ideas about geometry with Lie groups. As John notes, they provide a joint generalization of the Riemannian and Kleinian points of view about geometry. They also seem to provide a natural mathematical framework for thinking about the relation between GR and gauge theory. Besides the references given by Wise, one should also note that Kobayshi-Nomizu, the standard reference text among mathematicians on geometry from the point of view of connections, is very much inspired by the idea of a Cartan connection. It seems likely to me that if we ever figure out how to properly understand geometrically how to unify gravity and the standard model, these ideas will be part of the story (although much else will also be required, including an understanding of the role of spinors, and of the geometry behind quantization).
Finally, for comic relief, Kris Krogh pointed me to a talk by Michael Berry from a few years ago, where he describes his experience back in 1985 at CalTech when he was working on quantum physics and zeta-functions, and met up with some of the local string theorists:
I met one of them, who asked what I was working on. When I told him, he fixed me with a pitying stare. “Yes, we have zeta functions throughout string theory. I expect the Riemann hypothesis will be proved in a few months, as a baby example of string theory.”
Update: Several people have pointed out that the Susskind t-shirt or the report about it contain a typo. The correct reference is hep-th/0302219
Update: There’s an interview with me posted on Scienceline, the web-site of the NYU Science, Health and Environmental Reporting Program, with the title Stringing Up String Theory.
Update: Yet another interview, this one with Lee Smolin at IEEE Spectrum on-line, called Thread-bare Theories.
I once talked to our librarians about the peculiar inclusion of “foundations of physics” with the other physics books because it appears to be a philosophy journal. Apparently the LOC decides where it is shelved for most libraries.
Can I put in a plea for less scorn in physics? I don’t really want to defend the foundations of physics, as much of the research in this field really was, and probably still is, junk. But the dismissal of the whole field as garbage by the vast majority of mainstream physicists is, in my opinion, a large part of the reason that the profound differences between classical and quantum computation weren’t discovered earlier. The field of quantum computation was thus ignored by the mainstream and founded by crackpots, outsiders (such as me), and the occasioual genius who didn’t care what other people thought. This, of course, was greatly to my benefit. (I’ve changed my mind. More scorn! More scorn!)
If the string theorists are wrong, the scenario will undoubtedly be repeated in the case of quantum gravity. Is anybody paying attention to the work of Alain Connes, a genius and an outsider?
Peter Woit said “… Kobayshi-Nomizu, the standard reference text among mathematicians on geometry from the point of view of connections, is very much inspired by the idea of a Cartan connection. It seems likely to me that if we ever figure out how to properly understand geometrically how to unify gravity and the standard model, these ideas will be part of the story (although much else will also be required, including an understanding of the role of spinors, and of the geometry behind quantization). …”.
In that context, might it be useful to revisit the 1980s work of Meinhard Mayer, A. Trautman, et al, on the geometry of gauge theories, which work extended the 1960s Kobayashi-Nomizu material from a gauge physics point of view ?
Examples of such work include:
Hadronic Journal 4 (1981) 108-152;
and
New Developments in Mathematical Physics, 20th Universitatswochen fur Kernphysik in Schladming in February 1981 (ed. by Mitter and Pittner), Springer-Verlag 1981, especially the articles entitled
A Brief Introduction to the Geometry of Gauge Fields;
The Geometry of Symmetry Breaking in Gauge Theories; and
Geometric Aspects of Quantized Gauge Theories.
Tony Smith
http://www.valdostamuseum.org/hamsmith/
Peter Shor asked “… Is anybody paying attention to the work of Alain Connes, a genius and an outsider? …”.
Actually, Peter Woit has had at least two entries on this blog about Alain Connes:
December 2005 at http://www.math.columbia.edu/~woit/wordpress/?p=313
which has links to a Tehran interview and workshop
and
October 2006 at http://www.math.columbia.edu/~woit/wordpress/?p=482
The latter entry has links to
http://arxiv.org/abs/hep-th/0610241 (a paper by Chameseddine and Connes in which they calculate “… a Higgs mass around 170 GeV and a top mass compatible with present experimental value …”, clearly (in my opinion) the type of results that superstringers would love to have but have been unable to get)
and
http://www.newton.cam.ac.uk/webseminars/pg+ws/2006/ncg/ (a Cambridge workshop on noncommutative geometry)
as well as
a link to an interview with Connes at
http://www.arte.tv/fr/connaissance-decouverte/science/Paroles_20de_20chercheur/1350636.html
Tony Smith
http://www.valdostamuseum.org/hamsmith/
Peter Shor is right; we need more tolerance in Physics. On the other hand, there may be wisdom in Henry Ford’s aphorism: “History is bunk” (or did he mean Philosophy?). But the equivocal stance is a futile one. So I say — strength to Peter Woit, who is anything but equivocal.
There is also room in physics for folk like Eduard Prugovecki, a Toronto physicist-mathematician-philosopher who explored the prehistory of the String Wars (aka the Renormalisation Wars). A long and informative article of his is at:
http://individual.utoronto.ca/prugovecki/EpistemicPerspectives.html
It does not appear in the archives of this Blog, but should be more widely known.
Hi Peter,
[this is somewhat off-topic but closely related to your post]
You once blogged that Graeme Segal would conduct a seminar at Columbia during December. Has he held his seminar yet?
Michael,
Segal gave a long lecture at a one day conference organized by Dennis Sullivan at the CUNY Graduate Center in December. He also gave a long series of lectures here at Columbia this past semester.
The lectures were about various topics in QFT, and he is writing a book on the subject. I’ve been trying to think of various tactics that might encourage him to get the book done more quickly. One of them would be to put my own notes from his lectures on-line, but given their state, I decided that that would be mean. Some of this material is already in lectures that you can find on-line written up by Segal himself.
First of all, I can name the Anthropically attired physicist, but I’m not sure if he would want to be “outed”, so I’ll just send him a link to the post.
Secondly, Andy said, “I once talked to our librarians about the peculiar inclusion of “foundations of physics” with the other physics books because it appears to be a philosophy journal.”
It’s a physics journal alright, just not one that only publishes papers that calculate the cross-section of somethingorother. I realize that makes it not recognisable as physics to a large section of the physics community. Compare with Stud. Hist. Phil. Mod. Phys. if you want to see what a philosophy journal looks like. In my opinion, creating artificial boundaries between “physics”, “philosophy”, “mathematics” and even “computer science” these days is part of the problem with modern physics. Foundational questions are studied mainly by philosophers, physicists and mathematicians, but they each bring a different approach to the subject and have different goals in studying it, so we’re best off treating it as an interdisciplinary subject rather than cordoning it off as “philosophy”. In any case, who cares where Found. Phys. goes in the library? Is there anyone left who wouldn’t prefer to access it on the web instead?
On the other hand, I agree that Found. Phys. has had a rather checkered history. It has gone through eras where editorial policy was particularly bad, but right now it seems to be more or less on track, so have a look at a recent issue and see what you think. I’d urge caution in judging it too harshly though. After all, even the esteemed PRL contains a large proportion of misguided papers. Even if technically correct, they often do not have the significance for the subject claimed by the authors. The main difference is that PRL covers technical work at the forefront of modern physics, so it is difficult for a casual reader to judge the quality of papers outside their field. On the other hand, Found. Phys. covers the foundations of subjects that any educated physicist ought to know something about, so it is much easier to spot the garbage.
Found. Phys. is not the only journal that has gone through, shall we say, interesting periods. Look up Nature 251, 602 (1974) for an example.
If a paper uses the word epistemology, it is philosophy!
Michael Berry’s talk reminds me very much of Richard Feynman. The full text is here.
Re: Streater/Wightman, I would be grateful if some kind reader of this blog would find it in their hearts to update the Wiki entry for Haag’s theorem with authoritative, up-to-date information. This is, after all, one of the main things tackled by this book.
Re: Eduard Prugovecki – thank-you, Peter Jackson, for drawing attention to Prugovecki, who arguments against renormalization are more learned and eloquent than my own. I was sorry to see that he died relatively young.
Sorry: Paul, not Peter Jackson.
This was very nice to see in print:
http://www.mth.kcl.ac.uk/~streater/EPR.html
The whole Streater page is just pure fun!
-drl
Peter Shor – I don’t see Streater as being scornful at all, just wickedly sarcastic, almost like H. L. Mencken. You get the strong feeling he has looked deeply into many of these lost causes himself and knows why they fail, and like any good explorer, is pointing out the potholes and cliffs to avoid.
His comments about quantum cosmology, wave fn of the universe, many worlds etc are however genuinely and rightfully scornful. Perhaps there is not enough scorn in physics!
-drl
the correct hep-th number of Susskind’s article is hep-th/0302219
Kobayshi-Nomizu is a standard reference and needs to be more widely known among physics students, but look as you may, you will not see semi-Riemannian manifolds discussed. Also it is somewhat weak in that this standard reference on geometry contains not one picture in either of its 2 volumes. It reminds one of the criticism of Lamb’s Hydrodynamics — you can read it and still not know that water is wet.
Volume 2 of Spivak is vastly superior for a physicsist in that it gives a good analysis and motivation of the different approaches to connections, which is more what a physicist needs…in other words, if you really want to understand the history and motivation of the subject, read Spivak.
LDM,
I agree that Spivak is much more readable than Kobayashi-Nomizu. It’s much longer and does things in much more detail and at leisure. However, one thing I noticed when teaching a course on this and using both as a reference is that there are some pretty sizable chunks of Spivak where the proofs are more or less directly copied out of Kobayashi and Nomizu.
On the whole, Kobayashi-Nomizu is not a good book to learn the subject from. But once you know what is going on, it is an excellent reference, with beautifully concise arguments.
peter – a friend pointed that out about the Feynman lectures – useless didactically, but invaluable once you knew what was happening. I never reconciled myself to this idea, having learned math from Klein and physics from Sommerfeld. There is no reason to be obscure when writing a text.
-drl
Perry said, “If a paper uses the word epistemology, it is philosophy!”
I know this is meant as a joke and I can assure you that the humor is not lost on me. Similarly, you can tell you are in a philosophy talk if the speaker ever talks about “cashing out” an idea.
However, you can find an increasing number of papers that use the word epistemology, or at least its cousin epistemic, in good old Phys. Rev., since they are beginning to take foundations seriously again in the wake of quantum info and quantum computation. That either means that Phys. Rev. is now publishing philosophy, or that it is genuinely possible to write a paper that bridges the gap. I’ll leave you to decide which is the case.
If you can’t see the stars from Manhattan, then check out ASTRONOMY magazine: “WHAT IF STRING THEORY US WRONG? If it is, the dark matter, dark energy and cosmic inflation are in big trouble.”
I’ll take a look at the latest Astronomy, but dark matter, dark energy, and inflation really have nothing to do one way or another with string theory.
Not sure where to post this, but you and your book were mentioned in a year-in-review episode of Talk of the the Nation’s Science Friday. One of the panelists admitted to having written one of the most negative reviews of your book and spewed some ignorant nonsense. Thought you might enjoy listening to it and getting annoyed.
anon,
Thanks, but I think I’ll pass on the opportunity to hear more from K.C. Cole. Her review was by far the most amazingly bizarre one of the many I’ve seen. I made the mistake of wasting my time complaining to her that she had misrepresented what I wrote in the book about neutrinos. In response she wrote back to explain that she, unlike me, was an expert on neutrino physics and had lectured to physicists on the subject. Yesterday I was talking with someone who has worked her, but will resist the temptation to repeat what he had to say about her.
The webcast of the Science Friday segment to which anon refers above can be found at http://www.npr.org/templates/story/story.php?storyId=6696466 and the discussion of Woit’s and Smolin’s books begins at 30:40.
K.C. Cole is not a scientist — and certainly could not do a real neutrino calculation if her life depended upon it. NPR/sciencefriday should have its funds cut for exposing our children to her incompetence.
Peter,
[again, partially off-topic but relevant nonetheless]
Do you know when, approximately, Segal will post his notes on the arXiv and/or when his (presumed) book will come out?
Michael
Michael,
I didn’t get the impression Segal was close to having a book done, and I don’t think he intends to write up notes from these lectures, so unfortunately I think it will be a while before this material appears in a finished, public form.
“Is anybody paying attention to the work of Alain Connes, a genius and an outsider?”
I am 🙂 and it is a very difficult work to follow, in the side related to gravity. He is up to conjuring all his previous experience on KMS states plus the new work with Marcolli on Qlattices, in order to get a vision of gravity “as symmetry breaking”.
Is anybody paying attention? Yes. Will anybody dedicate the effort needed to follow him? I doubt it. At least in the gravity related issues. I am a bit more optimistic in the question of producing examples and or classification of spectral triples. And then there is the part about the standard model. Barrett at Nottingham was putting attention recently, and it receives sporadic attention from here and there, more or less at the level of any other GUT model.
K.C. Cole was a so-called “science reporter” for the Los Angeles Times a few years ago. I found nearly everything she wrote to be exceedingly annoying, both in style and content.
From what I’ve seen people are very aware of Connes work, but nobody really knows what to do with it.
I know that there are a couple of guys in Denmark trying to apply Loopy techniquees to Connes style geometry, but it’s tough from a technical point of view AND doesn’t really seem to conect to the conceptual physical questions that seem appropriate….
Ah yes, the reference is:
hep-th/0601127
Peter and others, happy holidays. Have a look at Steinn’s blog
http://scienceblogs.com/catdynamics/2006/12/dissed_by_the_best.php
on how he shifted from string theory to astrophysics
it would be interesting to have a presentation of Connes works in a style more accessible to physicists, focussed about their physical motivation and predictive power (does it restrict the QFT particle content and couplings?), rather than about applications to quantum gravity.
I don’t mean to be too discouraging, but I don’t see what is
so exciting about Connes’ approach to the standard model.
He takes a complicated, successful theory and makes
it even more complicated, just to facilitate his ideas. It
all seems badly motivated.
Peter – you actually should listen to Cole. I have never in my life heard such indescribable bullshit. How does this non-entity, who without doubt cannot even understand Aristotle, not to say Kepler or Galileo, much less Newton or Einstein or beyond, presume to tell an interested listener what physics is about?
It is extraordinary. Imagine if such a person gave medical advice, or piloting advice, or firefighting advice. “Well it’s only physics.” Wrong – physics is important. Most of modern life came from it.
I am stunned.
-drl
Michael Berry’s 1985 CalTech anecdote is extremely funny. But one shouldn’t overgeneralize. Caltech has, for a century or so, been a place where there are always SOME Mathematicians who listen to what Physicists are saying, and vice versa. John Schwarz is not a universal template, and is a gracious host at swimming pool parties I’ve attended.
The intersection once included, to pick a few luminaries almost at random, Harry Bateman, Dr. Robert A. Millikan, Dr. Theodore von Karman, Linus Pauling, Feynman, Gell-Mann, Witten, Stephen Wolfram, Hawking, and at the moment includes Barry Simon and Kip Thorne. The fact that it produced people second rate in both, such as myself, should not be held against it.
Peter Orland:
Connes actually has a prediction for the Higgs mass in his latest paper (hep-th/0610241). True, it seems to assume the probably incorrect “big desert hypothesis” that there’s no new physics between the Higgs scale and the Planck scale, but I believe this is still more than any of the alternative approaches can achieve. So it seems to me (who knows nothing about it) that Connes’ approach must be introducing some new constraints somehow. And since I know Connes is really smart, my opinion is that it’s worth paying attention to.
On the other hand, it looks very hard and I’m not planning to try to figure it out myself, so I probably shouldn’t be criticizing other people for not trying to figure it out themselves, either.
Peter Shor,
Please understand that though I admire Connes,
I don’t find the prediction of one number especially
impressive. Fits are not physics.
One needs a new idea (or a dramatice experimental
result) which is fundamentally simple. This is different
from being mathematically or calculationally simple.
By fundamentally simple, I mean a theory with few
hypothesis leading to a strong consistent framework
(like Maxwell’s equations or General Relativity).
Connes idea, to my way of thinking, is not simple
in this sense. No principle points to his non-commutative
scheme the way the principle of equivalence pointed
to Riemannian geometry into gravity.
P.S. (by which I mean Peter Shor)
I think it is better to find an idea interesting and
not pursue it (as you are doing), than dismiss an
idea because you don’t want to learn about it.
I hope that that is not what I am doing.
Many people in high-energy theory arrogantly
dismiss an idea as nonsense because they don’t
want to make an effort to understand it. I only
add this remark because I do not want my writings
above to reinforce this contemptuous behavior.
Peter Orland,
I didn’t mean to imply that you are one of the people who arrogantly dismiss ideas because they don’t understand them.
I have assumed that worrying about how to quantize space-time led to non-commutative geometry. Since I don’t understand any of this, I could be completely wrong.
Peter Shor
Peter,
I don’t think that quantization of space-time definitely
implies that geometry is non-commutative. Non-commutativity
is just one proposal.
All we are sure of is that there is some cut-off scale less
than or equal to the Planck scale 10^{-33}cm, at which
GR breaks down. This may have no implication for the
standard model (I can’t imagine how it wouldhave such an
implication).
Unless there is some fundamentally simple idea that
points to what should happen (by “fundamentally
simple”, I don’t mean easy to understand. See my above
remarks) there are lots of ways to cut off gravity.
Some schemes for cutting off gravity are more
philosophically attractive than others (depending
on your philosophy) but there is no compelling principle
yet which tells us how to chose. Some people would
chose string theory because of renormalizability or
finiteness, but it isn’t clear to me that it’s the only way.
An interesting problem would be to put in just a silly
momentum cut-off into gravity at the Planck scale and
ask if there are any observable consequences. For example,
there would be Planck-sized unitarity violation. That could
conceivably imply some nonconservation of probability
that one might be able to test. Maybe Kuzmin has thought
about this, since he and his collaborators had suggested that
violations of certain precepts at the Planck scale could have
macroscopic consequences.
One aproach would be to ask what sort of cut-off scheme
would naturally explain flatness. By this I mean both
approximate cosmological flatness and the fact
that space-time fluctuations don’t seem to grow to
macroscopic size (this is a problem in path integrals of
random manifolds). I had a crazy proposal to solve
this problem, which I called the “critical solid”, but
some of the assumptions of the proposal need
to be changed slightly. I eventally would like to look
at this problem again, but I am too busy with non-perturbative
aspects of gauge theories.
I just looked up V. A. Kuzmin’s papers on SPIRES. It seems he has
looked at violation of CPT at the Planck scale, but not of unitarity.
The requeriment of a “new idea” is sort of misleading. Gauge theories were stressed by Pauli, the nonabelian version from Yang-Mills can not score as a “radical new” idea, and the point of using SU(2) times U(1) would not score even as “new”.
It is more about ideas evolving in paralell to experimental input, and in this sense Connes´s model is performing well: it transmuted ten years ago to go from electroweak to include colour, and now in transmutes again to include neutrinos. Still, it is not definitive, because it is not really exploiting the new mathematical setup (for instance, the fact of SU(3) being separated from the electroweak part in the bivector field formulation, as it appears in the red book, would add some insight about the quarks and it doesn’t – yet).
Alejandro,
I didn’t say that I am skeptical of Connes’s idea because it is
not new. I am skeptical because it makes the standard model
more complicated and solves no problems. In this sense I don’t
think the idea is a fundamental advance.