Description
Matt loves thin shells, and who doesn't? But thin shells tend to be dynamically unstable to nonradial perturbations, and this limits their use in terms of modeling exotic astrophysical bodies (such as black-hole mimickers and even wormholes). After telling some stories about Matt and how we came to work together, I will describe some recent work (with Tristan Pitre and Berend Schneider) that establishes that self-gravitating thin shells are dynamically unstable in both Newtonian gravity and general relativity.