From generalized Poincaré to Poincaré-Sobolev inequalities via self-improving methods

Abstract

We establish several improvements to the main results of [PR19] and [CP21], refining the seminal self-improving method for generalized Poincaré inequalities from [FPW98, MP98]. These results, together with various related applications, stem from a general self-improving property for functions satisfying the local inequality $$\frac{1}{|Q|}{\int }_Q|f(x)-f_Q|dx\le a(Q)$$ for all cubes $Q\subset {\mathbb{R}}^n$. The functional $a$ is assumed to obey a specific discrete geometric summability condition. By restricting our focus to axis-parallel cubes in ${\mathbb{R}}^n$, this geometric setting allows us to obtain sharper estimates than those available in more general metric measure spaces.

39 pages