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Tuesday, October 08, 2013

Nobels for Higgs and Englert


Congratulations to Peter Higgs and François Englert on their Nobel prize. A bit of background from an earlier post How the Higgs boson became the Higgs boson:
IIRC, I met Peter Higgs in Erice in 1990. He was quite a nice fellow, but the story below by Steve Weinberg illustrates how capricious is the allocation of credit in science.

NYBooks: (Footnote 1) In his recent book, The Infinity Puzzle (Basic Books, 2011), Frank Close points out that a mistake of mine was in part responsible for the term “Higgs boson.” In my 1967 paper on the unification of weak and electromagnetic forces, I cited 1964 work by Peter Higgs and two other sets of theorists. This was because they had all explored the mathematics of symmetry-breaking in general theories with force-carrying particles, though they did not apply it to weak and electromagnetic forces. As known since 1961, a typical consequence of theories of symmetry-breaking is the appearance of new particles, as a sort of debris. A specific particle of this general class was predicted in my 1967 paper; this is the Higgs boson now being sought at the LHC.
As to my responsibility for the name “Higgs boson,” because of a mistake in reading the dates on these three earlier papers, I thought that the earliest was the one by Higgs, so in my 1967 paper I cited Higgs first, and have done so since then. Other physicists apparently have followed my lead. But as Close points out, the earliest paper of the three I cited was actually the one by Robert Brout and François Englert. In extenuation of my mistake, I should note that Higgs and Brout and Englert did their work independently and at about the same time, as also did the third group (Gerald Guralnik, C.R. Hagen, and Tom Kibble). But the name “Higgs boson” seems to have stuck.

[ Note that to Higgs' credit his is the only paper that clearly works out the properties of the excitation now known as the Higgs boson. ]
Jeffrey Goldstone showed (1961) that when rigid ("global") continuous symmetries are spontaneously broken by the vacuum (the vacuum configuration is not invariant under the symmetry), a massless boson necessarily results. This boson is the eponymous Goldstone boson: the particle excitation corresponding to small perturbations of the vacuum state in the direction of the symmetry. The natural next step is to ask what happens if the broken symmetry is a gauge (local) symmetry. This is the problem that Higgs et al. solved. But Goldstone had one of the first cracks at the problem. Indeed, Jeffrey deduced the existence of a massive excitation (i.e., the Higgs boson), but its physical reality was in question -- only apparent in certain "choices of gauge"; gauge theory was not then very well understood. According to legend, Sidney Coleman convinced Goldstone that the boson was only a gauge artifact. For years afterward Goldstone would say that Sidney, despite his obvious brilliance, was, when it really counted, always wrong!

I met Englert for the first time in 2008 at a workshop in Paris on the black hole information problem. Over coffee, he explained to me some mysterious comments 't Hooft had made in his talk. A real gentleman, and still very sharp.

A photo from the summer school in Erice, Sicily 1990. Higgs is in the blue socks and sandals, holding a glass of wine. I'm in a maroon shirt two rows back.


A portrait of Higgs in the physics department of the University of Edinburgh.

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