Geometric logarithmic-Hardy and Hardy-Poincar\'e inequalities on stratified groups

Abstract

We develop a unified strategy to obtain the geometric logarithmic Hardy inequality on any open set M of a stratified group, provided the validity of the Hardy inequality in this setting, where the so-called "weight" is regarded to be any measurable non-negative function on M . Provided the legitimacy of the latter for some open set and for some weight, we also show an inequality that is an extension of the "generalised Poincar\'e inequality" introduced by Beckner with the addition of a weight, and this is referred to as the "geometric Hardy-Poincar\'e inequality". The aforesaid inequalities become explicit in the case where M is the half-space of the group and the weight is the distance function from the boundary, and in the case where M is just the whole group (or any open set in the group), in which case the weight is the "horizontal norm" on the first stratum of the group. For the second case, the semi-Gaussian analogue of the derived inequalities is proved, when the Gaussian measure is regarded with respect to the first stratum of the group. Applying our results to the case where the group is just the (abelian) Euclidean space we generalise the classical probabilistic Poincar\'e inequality by adding weights.