Sometimes the real world and the blogosphere intersect, as they did yesteray.
Yemon Choi, from Saskatchewan, whose blog Since it is not … has been on my sidebar for quite some time and has survived my occasional culls, gave a talk at Queen Mary entitled “Commutative amenable operator algebras”. The talk had been advertised as “out-of-exam entertainment”: how could I resist?
Banach algebras are not my field, but I suspected that bloggers on average give better talks than non-bloggers. This one certainly confirmed the theory.
It was subtitled “A partial survey”, and Yemon explained that this had two meanings: he was not covering everything, and he is not impartial about the topic.
I thought it was brave to go from 2×2 matrices on the second slide to amenable groups on the third; but it was all slowly and clearly explained on the board, and I was able to get a feel for what is going on. There is a notion of amenable Banach algebra, one whose representations have a kind of Maschke property, closed invariant subspaces have invariant complements. (That isn’t the definition!)
I must apologise publicly to Yemon that I couldn’t stay after the talk; I had to dash off to the next thing. (So much for leisurely retirement!)