The Dirichlet problem for elliptic and degenerate elliptic equations, and related results

Abstract

In this thesis, we first prove the solvability of Dirichlet problem with Lp data on the boundary for degenerate elliptic equations. Second, We obtain Lp bounds semi-groups and their gradients, and then we get Lp bounds for Riesz transform and square functions associated to a degenerate elliptic operator in divergence form. Finally, we show that for a uniformly elliptic divergence form operator defined in an open set with Ahlfors-David regular boundary, BMO- solvability implies scale invariant quantitative absolute continuity of elliptic-harmonic measure with respect to surface measure.