Regularity estimates via the entropy dissipation for the spatially homogeneous Boltzmann equation without cut-off

We show that in the setting of the spatially homogeneous Boltzmann equation without cut-off, the entropy dissipation associated to a function f Î L1(RN) yields a control of vf in Sobolev norms as soon as f is locally bounded below. Under this additional assumption of lower bound, our result is an improvement of a recent estimate given by P.-L. Lions, and is optimal in a certain sense