Last week the CUNY Graduate Center hosted a conference in honor of the 75th birthday of Jim Simons. It was organized by Dennis Sullivan as a set of expository “mini-courses” on various topics related to Simons’ mathematical work. I was able to attend the morning talks, which were of a uniformly high quality, and focused on the Chern-Simons 3d QFT, as well as the “differential characters” of Cheeger and Simons. Video of most of the talks is available online here. In particular, Witten’s talk, which was a very simple physical introduction to use of the Abelian Chern-Simons term in condensed matter, is available here (followed by Deligne on Deligne-Beilinson cohomology). Talks by Robbert Dijkgraaf on Chern-Simons-Witten theory are here and here. The second Dijkgraaf talk was followed (go to 1:05) by some informal comments by Simons himself, explaining the history of how Chern-Simons came about. Mike Hopkins gave two wonderful talks, the first about differential characters in general and about his recent article with Dan Freed, the second about his work with Singer that used generalized differential cohomology.
The talks I missed were likely just as good, I’m starting to catch up on them on video now….