Quantum numbers, Chern classes, and a bodhisattva

For two and a half years, starting in January 1946, I was a graduate student in the physics department of the University of Chicago. During that period Enrico Fermi often joined several of us for lunch in a campus cafeteria called the Commons. Among those participating were Marvin Goldberger, Geoffrey Chew, Owen Chamberlain, and Joan Hinton. Later Marshall Rosenbluth, T. D. Lee, and others also joined. Once in 1948 Fermi brought a short and lean Frenchman to the cafeteria. That day it was mostly the two of them who talked. Afterwards we asked Fermi who that person was, and he said it was André Weil, an important mathematician. He also said Weil was speculating that the new particles and quantum numbers physicists were finding might be related to a classification scheme that mathematicians were developing in geometry and topology. None of us at the time understood what Weil had meant....