Commutative Algebra and Algebraic Geometry: The Fellowship of the Ring: Moment Varieties of Measures on Polytopes

Seminar | October 23 | 3:45-4:45 p.m. | 939 Evans Hall

 Bernd Sturmfels, MPI MIS, Leipzig

 Department of Mathematics

The uniform probability measure on a convex polytope induces piecewise polynomial densities on the projections of that polytope. For a fixed combinatorial type of simplicial polytopes, the moments of these measures are rational functions in the vertex coordinates. We study projective varieties that are parametrized by finite collections of such rational functions. Our focus lies on determining the prime ideals of these moment varieties. Special cases include Hankel determinantal ideals for polytopal splines on line segments, and the relations among multisymmetric functions given by the cumulants of a simplex. In general, our moment varieties are more complicated, and they offer nice challenges for both numerical and symbolic computing in algebraic geometry. This is joint work with Kathlen Kohn and Boris Shapiro.