Hard spheres are routinely studied as model particles in statistical mechanics. However, the underlying phase space or energy landscape seems to not be very well understood, even for systems of a small number of particles. On the other hand, understanding the topology and geometry of such spaces, including basic questions such as connectivity, is of intrinsic interest in mathematics and physics.
I will report on some recent progress in understanding topology of such spaces, both theoretically and computationally. The talk will survey work from a few papers, including joint work with several people: Yuliy Baryshnikov, Peter Bubenik, Gunnar Carlsson, Jackson Gorham, Robert MacPherson, and Jeremy Mason.