Time Compactness Tools for Discretized Evolution Equations and Applications to Degenerate Parabolic PDEs

We discuss several techniques for proving compactness of sequences of approximate solutions to discretized evolution PDEs. While the well-known Aubin-Simon kind functional-analytic techniques were recently generalized to the discrete setting by Gallouet and Latche [15], here we discuss direct techniques for estimating the time translates of approximate solutions in the space L-1. One important result is the Kruzhkov time compactness lemma. Further, we describe a specific technique that relies upon the order-preservation property. Motivation comes from studying convergence of finite volume discretizations for various classes of nonlinear degenerate parabolic equations. These and other applications are briefly described.