Relative Nash-type and $L^2$-Sobolev inequalities for Dunkl operators and applications.

We investigate local variants of Nash inequalities in the context of Dunkl operators. Pseudo-Poincar\'e inequalities are first established using pointwise gradient estimates of the Dunkl heat kernel. These inequalities allow to obtain relative Nash-type inequalities which are used to derive mean value inequalities for subsolutions of the heat equation on orbits of balls not necessarily centered on the origin.