Some Articles

Well, as I mentioned in the last post, Sunday’s symposium at the AAAS meeting in Chicago went very well, and we successfully communicated a lot of the physics results, ideas, and excitement to the audience. One of the team, Peter Steinberg, did a blog post, and he’s also got some more pictures that you’d perhaps like to see.

Some of the journalists who were there have already produced some pieces reporting on the physics. It is actually interesting to see all their different takes on the same presentation and discussion event. So far, I’ve seen the one by Glennda Chui at Symmetry Breaking, which had the mixed blessing of being tagged by Digg (the server was down for hours as a result!), one at Physics World by Margaret Harris (this one sort of missed the key physics point a bit – see below), one at the Discovery Space Blog by Dave Mosher, and one by John Timmer at Ars Technica (He misquotes me a little here and there, but I do like the “String Theory Officially Useful” phrase in the title!). [Update: There’s also an AAAS publication here.]

Anyway, as I said, I think that the Physics Today one sort of got sidetracked a touch and so I placed a comment there to clarify some points. I realized that they might be useful to some reading here, and so I reproduce it here. Enjoy:

Hi Margaret,

Thanks for the post on this. A few key remarks are in order:

(1) I did not focus on the “minimum” issue largely because that is not really the issue at all (and further, I prefer to use the word “natural” value, not “minimum” value, since it is only a conjecture that it is a minimum).

(2) The reason lots of us are excited is because the experimental results are creating a phase of matter in a regime where the traditional techniques for those disciplines do not do so well at describing their unexpected properties (it is a strongly coupled system), or at least use extremely complicated methods to make sense of small portions of it. On the other hand, rather simple computations in these models constructed using string theory with quantum black holes in higher dimensions seem to naturally describe just the kind of fluid phases with the unusual properties experimentally observed. This is exciting. Good open-minded physics uses good robust tools wherever they can be found, and there is an emerging picture (that still needs more research to see how far it goes) that says the the right organizational tool for getting at the physics in question is string theory, which is rather nice for a lot of reasons. How far this can be pushed is a matter of further research, as should always be the case with any methodology.

(2) You, perhaps unintentionally, made it seem like there was is just one little number that is being discussed. Actually, it is a _whole_ _class_ of behaviour that is being captured experimentally, and described theoretically by the string theory methods, with several measurable quantities associated with them. The precise behaviour of the energy density of the fluid with the temperature is one of the first signs that it is not behaving as an ideal gas. This is one of the simplest analytical computations you can do with the string models, and it comes out quite readily to match what was eventually inferred from the experiments. The behaviour of probe quarks as they shoot through the fluid displays a striking shock wave – again something that you see beautifully in the string computations…. and so on and so forth. For further reading on the RHIC side of things, I recommend looking at a review by, for example, Ed Shuryak.

(3) An important point to emphasize overall is that there’s something quite marvellous emerging. The string theory work shows that there is a reasonably wide class of fluids with very specific (and from some perspectives) unexpectedly peculiar properties. That’s nice in itself, but the great thing is that examples of this class of fluid seem to be showing up in two (so far) experimental contexts. That’s, I think, the best way of stating the content of the prediction, if the term provocative term “prediction” need be used at all. From a physics perspective, I find this rather exciting. New behaviour of matter is found in the lab and there is a theoretical framework in which this behaviour readily emerges and can be described.

I talk a lot more about this on my blog, by the way (including further reading, etc.) For example, see a report I did on a 2007 workshop on some of this:

http://asymptotia.com/2007/08/22/exploring-qcd-in-cambridge/

Best,

-cvj