Abstract: 

Kerr and Kerr-de Sitter spacetimes are families of rotating black holes. They are parameterized by their mass and angular momentum. We discuss propagation of singularities of wave equations on Kerr-de Sitter spacetimes. We construct a new pseudodifferential operator algebra using a fractional blow up and prove a propagation estimate improving the result of Peter Hintz. The key feature we use is the normally hyperbolic trapping of the associated Hamiltonian dynamical system.