Philip Anderson 1923-2020

I heard this morning about the death yesterday of Philip Anderson, at the age of 96. It’s not hard to make the case that Anderson was the most important condensed matter theorist of the twentieth century, with a huge influence on how we think about the subject. I believe he was even responsible for the name “condensed matter”. There are already obituaries at Princeton, and at the New York Times. For more about his work, Douglas Natelson has written something here.

Anderson’s career intersected with the field of high energy physics in several ways. Most importantly, what is often called the Higgs phenomenon really is a discovery of Anderson’s, and this should have been recognized by a second Nobel for him (he already had one for some of his work in condensed matter). I’ve written extensively about this story on the blog, see for example here, here and here. The story is a bit complicated, but it’s undeniable that in November 1962 Anderson submitted the paper Plasmons, Gauge Invariance and Mass to the Physical Review, and it was published on April 1, 1963. This was more than a year before the Higgs/Brout/Englert/Guralnik/Hagen/Kibble papers that HEP theorists always point to as the original ones. If you read Anderson’s paper, you’ll find a discussion of the “Higgs mechanism” which gets at the basic physics in much the same way we think of it today. There was no reason for HEP theorists to miss this paper, Anderson had written and published it not as a condensed matter paper, but as a contribution to current high energy theory. The only counter-argument I’ve gotten about this is that “Anderson’s explicit model was non-relativistic”, but this is a physical phenomenon for which relativity is not particularly relevant. Does it really make sense to argue that recognition should not go to a theorist who discovers a new phenomenon, but to others who later show that a possible problem (e.g. inconsistency with special relativity) not considered by the discoverer really isn’t there?

My time as a student at Princeton during 1979-84 (during which years Anderson split his time between Princeton and Bell Labs) was a high point of interaction between the condensed matter and HEP theory groups. HEP theorists trying to understand QCD investigated many examples of non-perturbative quantum field theory behavior that were of common interest with Anderson and others working on condensed matter. Anderson did have a major philosophical difference with the reductionist point of view of many HEP theorists, with his 1972 paper More is Different providing a strong critique of reductionism and emphasizing the importance of emergent behavior. In some sense, leading HEP theorists in recent years have come around to his point of view, often working on emergent models of space-time, with little interest in what microscopic physics space-time might be emerging from.

Anderson made no friends among the HEP community when he came out in 1987 against building the SSC (which was cancelled in 1993), for more about this, see this blog entry. He was also a skeptic about string theory, which perhaps made for some discomfort as Princeton HEP theory centered around this subject starting in 1984.

The two personal interactions with Anderson that I remember both involved him providing me with significant encouragement. When I took my general exams at Princeton, one component was an exam on condensed matter theory. This was not then and is not now a subject I know much about. After the exam there later was a gathering of students and faculty, and Anderson came up to me to tell me that he had graded my condensed matter exam. On one problem evidently I had gone about it wrong, but at some point had stopped and written that the result I was getting wasn’t sensible. Anderson complimented me on this, telling me that knowing when a calculation wasn’t making sense was an important skill. This was the nicest way imaginable to encourage a student who didn’t really know what he was doing.

Twenty years later, in early 2001, after I had written this article and had distributed it to several theorists including Anderson asking for comments, this is what he wrote back to me:

(Jan 19, 2001)
Dear Peter, I’m sorry to have been so slow to get back to you; my printer blew out when I tried to print out your attachment. When I finally got it it blew my mind–I loved seeing my vague misgivings made explicit. I would say that perhaps a stronger argument is the way of coping with black hole entropy, but since hearing about that i have never had it made clear to me that the story is unique to string theory except as a representative of sane quantum theories of gravity–the point made is that the gravitational theory provides its own cutoff.

I would hope but wouldn’t guarantee that P Today would publish it–I would be glad to introduce you as a guest columnist but they might not accept that.

When Lewontin and friends wanted to do a similar, but less well justified, job on sociobiology they wrote a broadside for the New York Review of Books.Since there are so many popular books I see no reason not to do that. If that doesn’t work I could perhaps insert you into John Brockman’s “third culture” chat room.. Anyhow, good luck–pwa

I wrote back to Anderson, telling him in particular that a prominent theorist had advised me not to publish the piece, since it would be counterproductive and the problems I discussed were well-known. He responded:

(Jan 23, 200)
Dear Peter, thanks for your reply. Of course [Prominent Theorist] would feel that the article would be counterproductive. Wasn’t that just the point? And to whom is it all well-known? The general public? Deans and department chairmen who make the hiring decisions? Science journalists who create the buzz? Politicians and bureaucrats who control the purse strings? Bullshit!

Yes, i agree that the version you sent me was too technical for a general journal like the NY review, but actually not much–the Lewontin arguments were pretty technical. Anyhow, good luck with this one. I showed it to a knowledgeable colleague, not a stringy but one who collaborates with them, and he also liked it.–pwa

Anderson then put me in touch with an editor at Physics Today. They decided not to publish the piece, first suggesting that instead I write a letter to the editor, and finally rejecting even that as “too inflammatory”. Anderson’s positive response to the piece though provided significant encouragement for my decision to start writing publicly about this issue.

He was one of the greats, and will be missed.

Update: More about Anderson from Physics World, Horganism, and Science magazine.

Update: David Derbes reminds me to point out that Higgs himself always properly credited Anderson, generally referring to the “Anderson mechanism”, or more specifically describing what he had done as the “relativistic Anderson mechanism”. For instance, he wrote here:

I call this the relativistic Anderson mechanism because Anderson described it first: it was his misfortune not to do so explicitly enough.