Let p 1 and let (X, d, μ) be a complete metric measure space with μ Borel and doubling that admits a (1, p)-Poincar´ inequality. Then there exists e ε 0 such that (X, d, μ) admits a (1, q)-Poincar´ inequality for every q p−ε, e quantitatively. 1. Introduction Metric spaces of homogeneous type, introduced by Coifman and Weiss [7], [8], have become a standard setting for harmonic analysis related to singular integrals and Hardy spaces. Such metric spaces are often referred to as a metric measure space with a doubling measure. An advantage of working.
