Operator algebra seminar

Speaker:  Piotr Nowak (IMPAN)

Title: Warped metrics, spectral gaps and the coarse Baum-Connes conjecture

Abstract: The coarse Baum-Connes conjecture is a large-scale geometric variant of the Baum- Connes conjecture. In 1999 Higson showed that certain expanders are counterexamples to the conjecture. I will discuss the construction of a warped cone over a group action and show that the spectral gap for the action gives rise to the existence of a certain ghost projection with additional properties. This provides strong evidence that warped cones over actions with spectral gaps form a new class of counterexamples to the coarse Baum-Connes conjecture. This is joint work with Cornelia Drutu.