Exploring QCD in Cambridge

exploring qcd sign

So the conference here at the Newton Institute in Cambridge is simply marvellous. I’m so glad I came, and so happy that I was invited to attend and make a contribution to it by giving a talk and having discussions. It’s a rather splendid combination of experimentalists, phenomenologists, and various hardcore theorists of various sorts, and there are ideas just flying around and bouncing off the walls. The title is “Exploring QCD: Deconfinement, Extreme Environments and Holography”, (it’s organized by Nick Evans, Simon Hands, and Mike Teper) and the focus is very much the fascinating nuclear physics of heavy ion collisions at the RHIC experiment at Brookhaven, and the experiments to come on heavy ion collisions at the LHC at CERN. The latter is an aspect of the physics to be done at the LHC that you don’t hear about much because it is sidestepped in favour of discussions about the Higgs, origin of mass, supersymmetry, theories of everything – such as strings, microscopic black holes, extra dimensions and all that other good stuff. (See earlier discussions here, here and here.)

Well, the great thing is that there’s been plenty of discussion of black holes, extra dimensions, strings, and so forth at the conference because of a great deal of promise of its relevance to nuclear physics. It’s been right alongside the discussion of experimental results, and other theoretical approaches such as work on computer simulations of aspects of QCD (“lattice QCD”) and studies involving other techniques. There’s very much a spirit of open-minded exchange among all the various parties […] Click to continue reading this post

The Scary Universe?

Ok, there’s “The Elegant Universe”, and “The Ambidextrous Universe”…. even “Stephen Hawking’s Universe”… and so on for these titles. But how about “The Scary Universe” or “The Dangerous Universe”? (Personally, I wish we’d just stop with the whole “The fill-in-the-blank Universe” stuff, so I probably should have not written this first paragraph.)

Well, I myself don’t think of the Universe that way, but tonight (at 9:00pm) the History Channel will be presenting the next show in their series (called “The Universe”), which is about (they say) the Most Dangerous Place In The Universe”. It looks as though it will be a survey of various places where a lot of very energetic activity is taking place, powering some of the most powerful phenomena we’ve ever seen, such as quasars, magnetars, and so forth. So black holes will feature quite a bit, I imagine, and although I probably should not really be telling you about it before I’ve had a chance to see it (recall my remarks about the windy shooting conditions here), I think (I’m not sure) that I’ll be making an appearance as one of the contributors. (I did not get caught off guard this time.)

The whole “dangerous” motif is a sort of deliberately sensational way of presenting […] Click to continue reading this post

News From The Front, VI: Simultaneity

aspen from gondolaI stopped the previous post rather abruptly (I had to do another task and then run some errands) without getting to tell you a little twist at the end of the story. Here it is.

Having chipped away at the thoughts that Strominger’s talk stirred in my head for several days last week, scribbling equations to check that all I was thinking was on the right track (and chatting a couple of times with Nick Halmagyi), I decided that it was all fitting together so nicely that the framework and my extensions of it just had to be true. There was that feeling that it was too nice to be wrong, and it passed all the obvious checks I could think of. There were two independent consistency checks everything had to pass (using my way of formulating things) and they gave exactly the right results as required by the general setup, with no room for maneuver.

When that happens so nicely, usually at that point in thinking about a physics problem, a thought occurs to me. If I’m playing with a good idea and everything is working so well, then there’s at least 200 other people in the field who probably are also playing with it, and 199 of them have way more time than I do to think it through and write it up before I can. One should not really worry about these things in an ideal world, but I’d be lying to you if I said it did not come up as a concern from time to time. I’ve a history of having my thunder stolen out from under me several times in the field (and not always accidentally), so I’m a bit gun shy.

Anyway, I started writing a draft of the paper on Thursday the way I usually do: I write […] Click to continue reading this post

News From The Front, V: Microscopic Weekend Diversions

I’ve been spending the day so far as an administrator, and not a researcher, since I have to present the results of two committees’ deliberations at one of the big annual organizational meetings tomorrow here at the Aspen Center for Physics. So I’ve been gathering and arranging data in a presentable form. Enough. I will take a break and blog a tiny bit before turning to a truly riveting task – reviewing an introductory physics textbook for a publisher… (Sigh…it is not so easy to escape these things out of semester time.)

I had big plans to do a hike each day on the weekend, but physics intervened. I should explain a bit more. Earlier last week I eventually got around to following Nick’s suggestion from an earlier post to take a look at Andy Strominger’s Strings 2007 talk entitled “Search for the Holographic Dual of N Heterotic Strings”. It was the usual nice Strominger talk, where he motivates the physics very well, and presents interesting and clear D-branesthoughts on the problem in hand. I shall try to say a bit more about what it is about later on, but the general gist of it is that it is to do with understanding certain types of four dimensional black hole in string theory. As you may know, one of the extraordinarily successful results in string theory in the last decade (and slightly more) has been that we can understand one of the most central results of semi-classical quantum gravity -that they have an entropy and behave like thermodynamical objects (the work of Bekenstein and of Hawking from the early 70s)- in precise terms in the full theory of quantum gravity that string theory appears to present us with. This started with the work of Strominger and Vafa in 1996, that showed how to describe a large class of black holes as essentially made of extended objects called D-branes (about which I’ve spoken at length earlier1).

Just to fill in the gaps roughly: Hawking’s result that black holes can radiate as thermodynamical objects comes from taking Einstein’s theory of General Relativity and combining it with Quantum Mechanics in a partial way. He could not really do much better since there was no proper quantum theory of gravity at the time, but even in […] Click to continue reading this post