Constructive stability results in interpolation inequalities and explicit improvements of decay rates of fast diffusion equations

TL;DR

This paper establishes improved decay rates for entropy in fast diffusion equations through stability analysis of Gagliardo-Nirenberg-Sobolev and Caffarelli-Kohn-Nirenberg inequalities, enhancing understanding of their long-term behavior.

Contribution

It extends stability results from GNS inequalities to CKN inequalities, providing explicit decay rate improvements without the need for well-prepared initial data.

Findings

Improved entropy decay rates for solutions of fast diffusion equations.

Extension of stability methods from GNS to CKN inequalities.

Explicit delay in decay rate improvement for CKN inequalities.

Abstract

We provide a scheme of a recent stability result for a family of Gagliardo-Nirenberg-Sobolev (GNS) inequalities, which is equivalent to an improved entropy - entropy production inequality associated with an appropriate fast diffusion equation (FDE) written in self-similar variables. This result can be rephrased as an improved decay rate of the entropy of the solution of (FDE) for well prepared initial data. There is a family of Caffarelli-Kohn-Nirenberg (CKN) inequalities which has a very similar structure. When the exponents are in a range for which the optimal functions for (CKN) are radially symmetric, we investigate how the methods for (GNS) can be extended to (CKN). In particular, we prove that the solutions of the evolution equation associated to (CKN) also satisfy an improved decay rate of the entropy, after an explicit delay. However, the improved rate is obtained without assuming that initial data are well prepared, which is a major difference with the (GNS) case.