COLLOQUIUM Widder’s Theorem for Dirichlet Spaces Dr. Nate Eldredge Visiting Assistant Professor Cornell University Abstract One of the simplest partial differential equations is the heat equation in Rⁿ, used to model heat flow and particle diffusion. A natural question about this model is whether solutions of the heat equation are uniquely determined by their initial conditions. In general, the answer is no, but a classical theorem of D. Widder gives a positive answer for nonnegative solutions. I will discuss this problem, giving some background on the heat equation and its connection to Brownian motion. I will then describe some recent work extending Widder’s result to the more general context of Dirichlet spaces, whose geometry can be quite pathological. Department of Mathematics Wednesday, March 7th, 2012 4:00 p.m. 204 Morgan Hall Refreshments will be served at 3:45 p.m.