For more information about this meeting, contact Nigel Higson.

Title: | Subspaces of groups and generalised Pimsner-Voiculescu extensions |

Seminar: | Noncommutative Geometry Seminar |

Speaker: | Jacek Brodzki, University of Southampton |

Abstract: |

A metric subspace X of a discrete group G carries a natural C*-algebra induced from the (right) reduced C*-algebra of the group. When the complement of X is not coarsely dense in G, there exists a homomorphism from the C*-algebra of X to the reduced C*-algebra of G which is part of a C*-algebra extension. Extensions of this type generalise those studied by Pimsner and Voiculescu in the case of free groups and groups acting on trees. I will illustrate this construction in a number of cases, including almost-invariant subspaces of groups, amalgamated free products, and others. An important motivation for this study is the problem of computing the K-theory of the reduced C*-algebra of G and I will indicate how our construction might help with that. |

### Room Reservation Information

Room Number: | MB106 |

Date: | 09 / 20 / 2012 |

Time: | 02:30pm - 03:30pm |