Paper detail

BMO solvability and the $A_\infty$ condition for second order parabolic operators

We prove that the $A_\infty$ property of parabolic measure for operators in certain time-varying domains is equivalent to a Carleson measure property of bounded solutions. Kircheim, Kenig, Pipher, and T. Toro established this criterion on bounded solutions in the elliptic case, improving an earlier result of Dindos, Kenig and Pipher for solutions with data in BMO. The extension to the parabolic setting requires an approach to the key estimate that primarily exploits the maximum principle. For various classes of parabolic operators, this criterion makes it easier to establish the solvability of the Dirichlet problem with data in $L^p$ for some $p$ (see results of Rivera-Noriega), and also to quantify these results in several aspects.