Michael Atiyah: Geometry and Physics Nigel Hitchin Mathematical Institute, Woodstock Road, Oxford, OX2 6GG
[email protected] December 31, 2020 1 Introduction Over the years, since I was a student, I experienced the many ways in which Michael Atiyah brought mathematics to life by importing new ideas, reformulating them in his own way, communicating them in his inimitable style and using these fresh insights to advance his own research. While in Oxford he would take every opportunity to travel to the USA and listen to what was currently interesting to him, then explain the results with his added contributions at his regular Monday seminar, hoping that some of these themes would be taken up by his audience. He was at heart a geometer, but in the mid 1970s he became convinced that theo- retical physics was by far the most promising source of new ideas. From that point on he became a facilitator of interactions between mathematicians and physicists, attacking mathematical challenges posed by physicists, using physical ideas to prove pure mathematical results, and feeding the physicist community with the parts of modern mathematics he regarded as important but were unfamiliar to them. Here is what he wrote in a retrospective view [24], producing two lists of the historical influences in both directions. It gives an impression of the weighting he applied to areas of the two disciplines. Mathematics ahead of physics: curved space, Lie groups, higher dimensions, fibre bundles, spinors, exterior algebra, non-commutative algebra, Hilbert space, special holonomy. Physics ahead of mathematics: infinite-dimensional representations, Maxwell theory, Dirac theory, supersymmetry, quantum cohomology, conformal field theory, quantum 1 field theory in 3 and 4 dimensions.