Not Even Wrong

Taking off tomorrow for a long weekend, internet access may be spotty. Here are some things that may be of interest:

HEPAP is meeting today and tomorrow, the presentations given at the meeting are available here.  JoAnne Hewett is there and has a posting on Cosmic Variance.
The Seed article with various physicist’s views about what to expect at the LHC that was discussed here earlier is now available online.

There’s an article about Jim Simons in Newsday (via Angry Physics).

Maybe a cosmologist can comment on the significance of this, but over at CosmoCoffee there’s a discussion of a new paper reanalyzing the latest WMAP data and coming up with a scalar spectral index n_s= .969 +/- .016. This is now 2.0 sigma away from 1, instead of the 2.7 sigma of the earlier analysis. This deviation from 1 was widely sold as evidence for inflation (since the simplest inflationary models give values slightly less than one), the fact that it is now only a 2 sigma effect seems to make this case a bit weaker.

The Institut Henri Poincare in Paris will be having a three-month-long program on Groupoids and Stacks in Physics and Geometry. The web-siter there contains a good associated overview of the subject.

Bruno Kahn has an excellent expository article on motives.

Over at the Edge web-site Lawrence Krauss has a piece called The Energy of Empty Space That Isn’t Zero. It’s partly about the cosmological constant, and discusses a workshop on Confronting Gravity that he organized back in March, which brought many prominent theorists together at a Caribbean resort to discuss physics, travel in a submarine, and hang out at the “private island retreat” of the funder of the event, science philanthropist Jeffrey Epstein.

Krauss has many provocative things to say about the current state of theoretical physics, including perhaps the most concise and vivid description I’ve read in a while:

It’s been very frustrating for particle physicists, and some people might say it’s led to sensory deprivation, which has resulted in hallucination otherwise known as string theory.

He also has a somewhat longer skeptical take on extra dimensions, together with an attempt at positive spin:

Many of the papers in particle physics over the last five to seven years have been involved with the idea of extra dimensions of one sort or another. And while it’s a fascinating idea, but I have to say, it’s looking to me like it’s not yet leading anywhere. The experimental evidence against it is combining with what I see as a theoretical diffusion — a breaking off into lots of parts. That’s happened with string theory. I can see it happening with extra-dimensional arguments. We’re seeing that the developments from this idea which has captured the imaginations of many physicists, hasn’t been compelling.

Right now it’s clear that what we really need is some good new ideas. Fundamental physics is really at kind of a crossroads. The observations have just told us that the universe is crazy, but hasn’t told us what direction the universe is crazy in. The theories have been incredibly complex and elaborate, but haven’t yet made any compelling inroads. That can either be viewed as depressing or exciting. For young physicists it’s exciting in the sense that it means that the field is ripe for something new.

I hadn’t realized how many of the physics departments at the top universities in the US have instituted undergraduate string theory courses.  The only one I was aware of was MIT’s 8.251, String Theory for Undergraduates, taught by Barton Zwiebach, who developed a textbook for the course, A First Course in String Theory. 

Maybe now that there’s a textbook, that is what has caused other institutions to follow suit.  Caltech has Physics 134, String Theory, and Carnegie-Mellon has Physics 33-652, An Introduction to String Theory.  Stanford goes its competitors one better by having two undergraduate courses in string theory: Physics 153A, Introduction to String Theory I, and Physics 153B, Introduction to String Theory II. This last course even promises to explain to students how string theory is connected to particle physics. 

Alex Vilenkin has a new popular book out about cosmology, entitled Many Worlds In One. It’s mainly about the extremely speculative end of cosmology, and much of it is devoted to explaining the author’s ideas on eternal inflation, creating the universe by tunneling out of nothing, and the anthropic landscape, together with stories about how he came to these ideas. It contains various amusing anecdotes, especially about Alan Guth. Sean Carroll is credited with the following story:

One of the leading superstring theorists, Joseph Polchinski, once said that he would quit physics if a nonzero cosmological constant were discovered. Polchinski realized that the only explanation for a small cosmological constant would be the anthropic one, and he just could not stand the thought.

He also describes the reaction to his anthropic arguments back during the years when these were not all the rage like they are now:

After one of my seminars, a prominent Princeton cosmologist rose from his seat and said, “Anyone who wants to work on the anthropic principle – should.” The tone of his remark left little doubt that he believed all such people would be wasting their time.

Vilenkin’s book covers much the same ground as Susskind’s, although from the point of view of a cosmologist, not a particle physicist. A huge amount is made of the supposed anthropic “prediction” of the value of the cosmological constant (any news of the rumor from Sean Carroll of new work by prominent Princeton cosmologist Paul Steinhardt showing this is bunk?). Unlike Susskind, Vilenkin at least doesn’t seem to be on a campaign to attack the “Popperazi” and convert everyone to anthropics, but he demonstrates a similar lack of concern for the fact that the ideas he is discussing don’t lead to much if anything in the way of a testable experimental prediction.

Here’s his scientifc program for 21st century physics, which he hopes will be spent working on the anthropic landscape:

First, we will need to map the landscape. What kinds of vacua are there, and how many of each kind? We cannot realistically hope to obtain a detailed characterization of all 10⁵⁰⁰ vacua, so some kind of statistical description will be necessary. We will also need to estimate the probabilities for bubbles of one vacuum to form amidst another vacuum. The we will have all the ingredients to develop a model of an eternally inflating universe with bubbles inside bubbles inside bubbles… Once we have this model, the principle of mediocrity can be used to determine the probablility for us to live in one vacuum or other.

Unfortunately for this research program, it has yet to even begin to get off the ground, and there are very good arguments that it can never succeed. There are an infinite number of possible vacua, and trying to make this finite so one can do statistics requires putting in cutoffs, with results then strongly depending on the cutoff. The large numbers of these vacua make any attempts to identify ones that agree with the real world computationally completely intractable. Even if one could do this, all evidence is that one would end up with broad statistical distributions for many of the parameters of the standard model, providing no useful prediction of what new experiments will see, or any insight into why these parameters have the values that they do.

The Cao-Zhu paper at the Asian Journal of Mathematics that is supposed to have a complete proof of the Poincare and geometrization conjectures is still not available, but the introduction to the paper has been posted there.

If you’re not getting enough string theory bashing today, head over to John Horgan’s Scientific Curmudgeon blog, where he has a posting entitled Pulling the Plug on Strings. It contains a wide selection of string-puns (or whatever you call such things), and he has decided to refer to string theory advocates as “yarn-heads” and braniacs. For his trouble, his comment section is under assault by the usual suspects. There’s also this site, containing a graphic mentioned here before which I refuse to admit to finding funny. The proprietors have an interesting way of dealing with the comment section.

Sabine Hossenfelder has an excellent posting on Science and Democracy.

This past week I’ve spent some time at the 26th International Colloquium on Group Theoretical Methods in Physics, being held here in New York at the CUNY Graduate Center. It was ably organized by Sultan Catto, who somehow convinced me to give a short talk on the blog and the book, one where I think I disappointed people by keeping string-bashing to a minimum. I enjoyed seeing people at the conference, and there were some good talks, including one by Greg Moore on his recent work with Dan Freed and Graeme Segal (see here and here).

Urs Schreiber has been putting his notes on-line about elliptic cohomology. Lots of interesting material, but his comment that he expects the landscape of superstring theories to be equal to the spectrum of elliptic cohomology sounds frightening. Maybe he means a different landscape…

I was quite sorry to hear of the recent death of Irving Kaplansky. Kaplansky was an algebraist, and director of MSRI when I was there in 1988-89. At the time I wasn’t much interested in algebra, so didn’t talk to him about math, but he was responsible for making MSRI a really wonderful place to work.

Update: The slides from Yau’s talk at Strings 2006 are now available here.

Slides from the talks at Strings 2006 are now available. I’ve spent a little while looking through them today, and am sorry I don’t have time to say much about them. Lots of more or less the same thing as in earlier years, and many talks devoted to complicated arguments designed to, as Eva Silverstein writes, populate, probe or constrain the Landscape. Nothing remotely like a plausible idea about how to ever get a prediction of anything out of this, but also virtually no anthropic arguments. I assume this was due to the iron fist of organizer David Gross.

I was pleasantly surprised to see that there were quite a few mathematically very interesting talks. Besides many talks of the sort that have been common in recent years dealing with the topological string, there were several that had nothing to do with string theory, but involved interesting mathematics related to QFT, and many of these had to do with work Witten is involved with, so they may get some attention. These were:

1. Witten’s own talk on Gauge Theory And The Geometric Langlands Program.

2. Kapustin’ talk on the same topic, entitled Topological reduction of supersymmetric gauge theories and S-duality.

3. Gukov’s talk on Surface Operators in Gauge Theory and Categorification, where he mentions that some of what he discusses is based on on-going joint work with Witten.

4. Nikita Nekrasov’s talk on Beyond Morse Theory.

So, as far as physics goes, the organizers are not allowing any talks on alternatives to string theory (the only mention of LQG seems to have been Dijkgraaf’s making fun of it), but they are willing to allow mathematical talks on QFT that are not related to string theory, especially since this is the field that Witten seems to be doing a lot of work in.

A couple people wrote in this morning to tell me about today’s Doonesbury, which features slacker Zipper Harris (who has a blog) trying to impress a woman he last saw in sophomore year of college. He’s still undecided about his major, but tells her:

I’m thinking physics.  Yarn theory.