We derive weak- and
strong-type global Poincaré estimates over s-John domains in spaces of
homogeneous type. The results show that Poincaré inequalities over quasimetric
balls with given exponents and weights are self-improving in the sense that they
imply global inequalities of a similar kind, but with improved exponents and larger
classes of weights. The main theorems are applications of a geometric construction for
s-John domains together with self-improving results in more general settings, both
derived in our companion paper J. Funct. Anal. 255 (2008), 2977–3007. We
have reduced our assumption on the principal measure μ to be just reverse
doubling on the domain instead of the usual assumption of doubling. While the
primary case considered in the literature is p ≤ q, we will also study the case
1 ≤ q < p.
Keywords
global Poincaré estimates, domains with cusps, δ-doubling, reverse doubling, power-type
weights, quasimetric spaces