Stability Results for Logarithmic Sobolev and Gagliardo–Nirenberg Inequalities

This paper is devoted to improvements of functional inequalities based on scalings and written in terms of relative entropies. When scales are taken into account and second moments fixed accordingly, deficit functionals provide explicit stability measurements, that is, bound with explicit constants distances to the manifold of optimal functions. Various results are obtained for the Gaussian logarithmic Sobolev inequality and its Euclidean counterpart, for the Gaussian generalized Poincaré inequalities and for the Gagliardo–Nirenberg inequalities. As a consequence, faster convergence rates in diffusion equations (fast diffusion, Ornstein–Uhlenbeck, and porous medium equations) are obtained.