Category Archives: research

Lookin’ For Some Hot Stuff

By | | , , , , ,
8 Comments

___________________________________________________________________________________
Hot, hot, hot, hot stuff
hot, hot, hot
hot, hot, hot, hot stuff
hot, hot, hot

– from “Hot Stuff”, by Donna Summer (1979). I refer to not only the physics but the c. 100 oF temperatures we’ve been having here every day recently.
___________________________________________________________________________________

On my way back from the conference, I spotted this book (left) last Saturday in Foyles (the booksellers) in London 1. Quark Gluon Plasma book It is a collection of reprints of a lot of the papers forming the foundations of the physics of the quark-gluon plasma (QGP) idea, going back the early to mid 1970s with such papers as Collins and Perry (Gosh, I had no idea Malcolm was one of the early workers on this idea. He’s much more thought of as associated with black holes, gravity, strings and so forth, ideas which – ironically – have recently turned out to be relevant to the discussions of the physics too. See my recent post, and there are also various popular articles to be found2).

Putting aside the usual ridiculous price that Springer Elsevier charges for books, I found myself in two minds about this book, in view of the surprises being uncovered about the properties of this remarkable state of matter at the RHIC experiment. Is this collection of early papers a useful working tool, or is it now just of historical interest, since many of the basic expectations about the properties of the plasma seem now to be incorrect?

rhic collision of gold ionsWell, after a bit of thought, I decided that the latter view would be way too hasty. First and foremost, on a general level, even if some of the computations in some papers were done in the “wrong” light (it’s a strongly coupled liquid that flows, not a weakly coupled gas of quarks and gluons), much of their content will still be useful in many ways – good and correct calculations last for all time, it is the sense of the words decorating them that may crumble over time. More specifically, one can worry about whether there were assumptions (and approximations based on those) that went into the computations that will render […] Click to continue reading this post →

Exploring QCD in Cambridge

By | | , , ,
25 Comments

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 →

Strings 2007

By | | , , ,
7 Comments

goya strings The main annual conference in my main field of interest starts today. Strings 2007 is in Madrid, and runs all week. The website is here (while there, have a play with the front page image of the Goya painting – quite entertaining). They promise to update the schedule/speakers page with scans of slides, and video, so you’ll be able to keep track of some of the new developments online. There’s no system for doing this live, or asking questions remotely, so if you want to quiz Ed Witten about his new 83-page monster paper on three dimensional gravity that came out yesterday (just in time for the conference!), or feel the buzz of event-anticipation whenever Witten talks about huge new sets of results, you’ll still have to show up in person.

Why am I not there? Well, it would be nice, but there are lots of reasons I’m not going […] Click to continue reading this post →

Hunting the Higgs is not a (D)Zero Sum Game

By | | , ,
9 Comments

D0 data shotWriting in Slate magazine, James Owen Weatherall seems a little confused about how particle physics works. Based on a rumour that there’s a new and significant signal seen at the DZero detector at the Tevatron at Fermilab (Illinois), one of the article’s titles is “Why the rumored discovery of the Higgs Boson is bad news for particle physics”. Supposedly, the big new machine, the Large Hadron Collider (LHC – see more about it here, and what physicists are hoping for from it), about to switch on later this year, would have nothing to do, and would be a waste of billions of dollars. You can read about the original rumour here.) (Above right: A random collision event I grabbed from the DZero experiment.)

Well, this is wrong for so many reasons. It is hard to know where to start with this. The major fallacy with the whole thing is that these machines are just somehow discovery devices (in the most naive sense) of some sort. You build it, switch it on, see what’s there, write the paper and the press release (not necessarily in that order) and then you’re done. Completely neglected is the notion of such an experiment as a device for […] Click to continue reading this post →

Read a Gravity Essay Today

By | | ,
1 Comment

The Gravity Research Foundation announced its awards for the 2007 essay competition. (Hmm: I think we should have more technical science essays, in more categories, to inform each other about what the big questions and answers are…. and maybe even just for fun (because I’m in a silly mood) -and to make an important point about how vital it is to communicate what we’re up to to each other- have a swanky awards ceremony, with speeches, and music, and an MC, and everything. And of course it should be held somewhere in LA… Like the LA Times Book Awards. It could be held at the same time as (another fantasy): awards we give to our peers for the important task of writing essays, books and other efforts in the service of communicating science to the general public.)

But anyway, you can read all about the winners of this year’s awards here. Nicking a bit of text from the site, here are the top prizes: […] Click to continue reading this post →

LHC Coverage

By | | , ,
6 Comments

CMS at LHC NYTimes

One of the Large Hadron Collider’s detectors, the Compact Muon Solenoid (CMS).

As you gather a lot when there are discussions on the topic here and elsewhere, there’s a lot of excitement and anticipation among high energy physicists about a number of things. I would go as far as to say that we are already in a very rich experimental time for results pertaining to high energy physics (or, if you insist, “fundamental physics” issues (I have in mind, for example, all the wonderful cosmological and astrophysical data that continues to come in, with more to come), and it is set to possibly get much richer – maybe even a new Golden Age with a little bit of luck – when the Large Hadron Collider starts producing results. We are really going into the (relative) unknown with this experiment, and this will be a great time to be working in the field – with a little luck, as I keep repeating.

A number of substantial articles have recently appeared in the general media that give you a good sense of what is going on, more reasons (and more detail) for why there is […] Click to continue reading this post →

Taking the Time to Work it out

By | | , ,
9 Comments

Itzhak BarsOne of my colleagues here at USC, Itzhak Bars (picture right, by Don Milici), spends a lot of effort trying to understand aspects of time. In fact, in his way of approaching things, the fact that we see a single time dimension (all the others being space dimensions) would be a consequence of certain choices (“gauge choices”, in the more technical language) made, whereas in the underlying formulation, there’s be two times. Yes, two.

You hear about extra dimensions, and you think “string theory”, no doubt. No, this is nothing to do with string theory. He’s developed this idea independently of string theory for years, working first with quantum mechanics, and […] Click to continue reading this post →

Quark Soup Al Dente

By | | , , ,
13 Comments

Here’s Rob Myers in action, giving Monday’s excellent departmental colloquium, entitled “Quark Soup Al Dente: Applied String Theory”:

robert c myers quark soup al dente

Here was his abstract:

In recent years, experiments at the Relativistic Heavy Ion Collider have discovered an exotic new state of matter known as the quark-gluon plasma. Simple theoretical considerations suggested that this plasma would behave like an ideal gas, however, the experiments show that it actually behaves very much like an ideal liquid. Thus the standard theoretical tools, such as perturbation theory and lattice gauge theory, are poorly suited to understand this new phase. However, recent progress in superstring theory has provided us with a theoretical laboratory for studying very similar systems of strongly interacting hot non-abelian plasmas. This surprising new perspective extracts the fluid properties of the plasma from physical processes in a black hole spacetime. At present, this approach seems to provide some of the best tools which theoretical physicists have to understand the heavy ion collisions at RHIC.

For a very good blog post on this issue, see Bee and Stefan’s post at Backreaction.

It was really excellent to see Rob and spend some time with him at dinner afterwards and at lunch the next day with my students. We got to chat over a nice Tapas-style meal and catch up a bit on what each other has been up to (both in and out of physics – Rob is one of my most long standing friends and collaborators in the field), and he even gave us a seminar on Tuesday before leaving.

Now, here’s a physics question for you: […] Click to continue reading this post →