Thursday, June 23, 2005

"More" really is different.

Condensed matter physics gets a bum rap sometimes. Murray Gell-Mann referred to it as "squalid state" physics. Wolfgang Pauli called it "Physik der Dreckeffeckte", or "the physics of dirt effects". (That's particularly ironic since it's the Pauli principle that makes condensed matter at all tractable.)

In addition to being at the heart of essentially all modern electronics technology, condensed matter is actually much more intellectually profound than "junk" effects. As Phil Anderson pointed out in his now famous essay, "More is different". That is, large systems of smaller entities interacting through relatively simple rules can exhibit very surprising emergent, collective properties. For example, a single iron atom is pretty simple, but put a bunch together, and you end up with a rigid solid (!) that is also a metal (!) and, at ambient conditions, a ferromagnet (!). Try predicting all that a priori from the Standard Model of particle physics....

One of my former professors, Bob Laughlin, has written a good book on this subject. As a physicist it's tough for me to judge just how well it'll read to a lay audience, but I enjoyed it thoroughly. It's vintage Laughlin (who I once saw ask a seminar speaker, "It's late. We're all tired. Why should we care about any of this?!"), even if some of the Stanford anecdotes have some minor inaccuracies. Here's a
review from the New York Times. I don't agree with everything he says (pretty much he thinks "nano" work is, in general, buzzword-laden crap rather than addressing real scientific questions. Oh wait - maybe I do agree with him.), but it's a fun read.

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