Weighted L² Estimates for Elliptic Homogenization in Lipschitz Domains

We develop a new real-variable method for weighted L^p estimates. The method is applied to the study of weighted W^{1 , 2} estimates in Lipschitz domains for weak solutions of second-order elliptic systems in divergence form with bounded measurable coefficients. It produces a necessary and sufficient condition, which depends on the weight function, for the weighted W^{1 , 2} estimate to hold in a fixed Lipschitz domain with a given weight. Using this condition, for elliptic systems in Lipschitz domains with rapidly oscillating, periodic and VMO coefficients, we reduce the problem of weighted estimates to the case of constant coefficients.