Abstract
When a singularity of a solution to the wave equation on a riemannian manifold reaches a point of conic
singularity of the metric, it undergoes a mixture of dispersive and geometric propagation first described
by Kalka-Menikoff and Cheeger-Taylor.  New notions of boundary wavefront set permit a simpler, more
conceptual approach to the problem, and associated positive commutator methods broaden the class of
manifolds on which we can work.  This is joint work with Richard Melrose.