This past weekend I was at the University of Central Florida, participating in a symposium organized by Costas Efthimiou of the physics department there. It was sponsored by two student organizations, the university’s Society of Physics Students and Campus Freethought Alliance. There were two speakers, Jim Gates and myself. I suspect that the organizers and many in the audience were hoping for some fireworks between Gates and myself, taking opposite sides on the controversy over string theory, but I fear that we disappointed them.
My talk was entitled The Challenge of Unifying Particle Physics, and my intention was to avoid spending much time going over the problems of string theory, since I’m pretty tired of that, and instead to try and explain to the audience some of the basic facts about symmetries, representations and quantum mechanics, together with an outline of the current state of efforts to unify physics. Gates gave a very general talk about particle physics, unification and string theory, featuring a lot of very impressive graphics he has developed as part of a multi-media course called Superstring Theory: The DNA of Reality.
In the end, there wasn’t that much for us to disagree about. My critique of string theory as a unified theory is based on the claim that the idea of using strings in 10d doesn’t work because the variety of possibilities for handling the extra 6 dimensions makes predictions impossible. Gates has always been skeptical about extra dimensions and wasn’t about to defend them, let alone the landscape. I take his general attitude to be similar to that of Warren Siegel, who he collaborated with in the past, and who explains his point of view here. Recently Gates has been very much interested in representation theory, in his case the representation theory of supersymmetry, where he and collaborators see fundamental problems still to be resolved, and have new ideas about using Clifford algebras to attack them. For one of their recent papers written from the more mathematical end of the problem, see here.
I very much enjoyed my time in Orlando; high points were getting to meet with and talk to some of the physics students there, meeting someone who sometimes comments here who came to the talk, and especially getting the chance to discuss things with Jim, who I found to be impressively knowledgeable and thoughtful about every topic that came up.