Math Notes

Notes I’ve written from time to time.

I participate in the Cambridge Advanced Math Study Group meetup. Right now, there are three “streams”:

  • Set Theory.
  • General Relativity. No page for this yet.
  • Lie Groups. No page for this yet

Logic and Set Theory

  • Scott’s Model of the Lambda Calculus. These are based on some notes I wrote up in the early 1970s, for a seminar on an early version of Dana Scott’s model of the untyped lambda calculus. These notes have nothing to say about Scott’s subsequent work on the typed lambda calculus, and the general notion of types. (Post)
  • Algorithmic Information Theory. I wrote these notes sometime in the early 90s, based mostly on Chaitin’s book Algorithmic Information Theory.
  • Two items on recursion theory: Friedberg’s Enumeration without Duplication (post) and Simple Sets (post).
  • John Baez and I have been having a conversation about non-standard models of Peano arithmetic (PA). I have converted the story so far into pdf documents, formatted both for a small screen and a  medium-sized one. I will update these from time to time (but not that frequently).

Other Stuff

  • I participated in a meetup group that went through Leinster’s Basic Category Theory. I wrote up solutions to many exercises, plus supplementary material.
  • Two notes on Stirling’s formula. First, easy derivations of parts of the formula, culminating in a determination of n! to within a factor of √2. Second, some notes some notes on Ahlfors’ derivation (in the 2nd edition of his Complex Analysis).