# T-duality for nonprincipal circle bundles and noncommutative geometry

## GAP Seminar

## Meeting Details

For more information about this meeting, contact Nigel Higson, Mathieu Stiénon, Ping Xu.

**Speaker:** Jonathan Rosenberg, University of Maryland

**Abstract:** "Topological T-duality", which was first discovered by physicists, gives an involution on the set of pairs (p: X --> Z, H), where p: X --> Z is a principal S^1 bundle and H is a 3-dimensional cohomology class on X. Recently David Baraglia pointed out that this theory can be extended to cover the case of nonprincipal circle bundles as well. In recent work with Varghese Mathai, we show that Baraglia's results can be reproduced in two ways: a) via a homotopy-theoretic approach Ã la Bunke-Schick, and b) via noncommutative geometry and crossed products. The latter method leads to the general analysis of K-theory for crossed products by the semidirect product of Z/2 acting on the reals.

## Room Reservation Information

**Room Number:** 106 McAllister

**Date:** 11/06/2012

**Time:** 2:30pm - 3:30pm