Type: Seminar

Distribution: World

Expiry: 18 Mar 2019

CalTitle1: Algebra Seminar: V, J--T, F and L

Auth: kevinc@pkevinc.pc (assumed)

Richard Garner (Macquarie University) Friday 1 March, 12-1pm, Place: Carslaw 375 Title: V, J--T, F and L Abstract: Thompson’s group V is a group of certain self-homeomorphisms of Cantor space. It also admits a combinatorial description, due to Higman, in terms of "Jonsson--Tarski algebras"---sets endowed with a bijection X --> XxX. The first part of this talk explains how these two perspectives on V can be unified via sheaf theory, making using of some results of Peter Freyd. Thompson’s group F is a group of certain self-homeomorphisms of the unit interval [0,1]. It also admits a combinatorial description in terms of a generalised notion of Jonsson--Tarski algebra due to Tom Leinster. The second part of this talk explains how these two perspectives on F can be unified via sheaf theory, making use of some apparently novel results involving a curiously augmented version of [0,1].