A last-minute extra talk was scheduled on the Wednesday morning at the Banff meeting – Assaf Naor on Superexpanders.  I would have loved to attend that talk, but I had a prior commitment to Aftenroe, a beautiful eight-pitch limestone climb above the road to Lake Louise.

Fortunately, thanks to the video system at BIRS, this doesn’t mean that I missed the talk.   One can find the excellent video of the talk here.  It’s a great presentation, as gratifying and elegant as Aftenroe‘s third pitch.  Below, I will try to describe some of the ideas. Continue reading →