Preprint: A simple description of Thompson's group F

The following paper is available: "A simple description of Thompson's group F" Marcelo Fiore, Tom Leinster We show that Thompson's group F is the symmetry group of the "generic idempotent". That is, take the monoidal category freely generated by an object A and an isomorphism A \otimes A --> A; then F is the group of automorphisms of A. http://arxiv.org/abs/math.GR/0508617 Incidentally, this is a result about groups, but the proof uses some higher-dimensional category theory (multicategories, operads, and, less essentially, bicategories). Tom