Topology and Azumaya algebras

An Azumaya algebra is something that is "locally" isomorphic to a matrix algebra. By varying the sense of "locally", we arrive at different incarnations of the concept. The motivating example is that of central simple algebras over a field. In this talk, I will concentrate on the topological aspects of the idea. I will give examples and show that the flexibility of topology allows one to produce counterexamples in algebra. At the end, I will mention some problems I do not know how to solve.