30 mar 2011

Abstract.

Dipartimento di Matematica - Sala Riunioni - ore 18:00

ABSTRACT: According to the general idea that ``the limit of the gradient-flows is the gradient-flow of the limit functional'', we prove an abstract result for passing to the limit in the theory of maximal slope curves in metric spaces, and then we apply this result to the study of the Perona-Malik equation. In a recent paper, P. Guidotti introduced a mild regularization of this problem. We prove that solutions of the regularized problem converge, in a slow time scale, to solutions of the total variation flow. The convergence result is global-in-time, and holds true in any space dimension. Then we consider the long time behavior of the semidiscrete scheme for the Perona-Malik equation in dimension one. We prove that the rescaled approximated solutions converge to solutions of a limit problem. This limit problem evolves piecewise constant functions by moving their plateaus in the vertical direction according to a system of ordinary differential equations. In this case, the main difficulty is the renormalization of the functionals after each collision in order to have a nontrivial Gamma-limit for all times. (Joint works with Massimo GOBBINO)