Hypocoercivity and global hypoellipticity for the kinetic Fokker-Planck equation in $H^k$ spaces

TL;DR

This paper extends hypocoercivity and hypoellipticity results for the kinetic Fokker-Planck equation from $H^1$ to higher Sobolev spaces, introducing modified norms and applying to mean-field models like the Curie-Weiss.

Contribution

It develops a new method to establish hypocoercivity in $H^k$ spaces by modifying norms with mixed terms, and applies these results to mean-field models, including the Curie-Weiss.

Findings

Optimal regularity estimates in short time.

Extension of hypocoercivity to higher Sobolev spaces.

Application to mean-field models like Curie-Weiss.

Abstract

The purpose of this paper is to extend the hypocoercivity results for the kinetic Fokker-Planck equation in $H^1$ space in Villani's memoir \cite{Villani} to higher order Sobolev spaces. As in the $L^2$ and $H^1$ setting, there is lack of coercivity in $H^k$ for the associated operator. To remedy this issue, we shall modify the usual $H^k$ norm with certain well-chosen mixed terms and with suitable coefficients which are constructed by induction on $k$. In parallel, a similar strategy but with coefficients depending on time (c.f. \cite{Herau}), usually referred as H\'erau's method, can be employed to prove global hypoellipticity in $H^k$. The exponents in our regularity estimates are optimal in short time. Moreover, as in our recent work \cite{GLWZ}, the general results here can be applied in the mean-field setting to get estimates independent of the dimension; in particular, an application to the Curie-Weiss model is presented.