Items for Jan16-Jan19

I was reading chapter 9 of Loop Groups but now have moved back to chapter 5. I had skipped over it trying to get to the representations of but chapter 5 is where they discuss the root system in .

I really enjoyed the talks I went to at U Chicago last week. Besides categorification and quantum groups which both seem fascinating, toward the end the speaker did touch on but in some sense more subtle a notion than . Something about “homotopy fiber product” or something like that with regard to a diagonal map. I wish I could post the commutative diagram. Anyway if I do get distracted this week by those things I’d rather get distracted about the material rather than the first two.