On the boundary estimates for second-order elliptic equations
M. V. Safonov · Complex Variables and Elliptic Equations · 2018
Consider uniformly elliptic equations in general form in a domain . We discuss the minimal assumptions on the boundary of which guarantee the existence or non-existence of Hopf–Oleinik estimates for solutions, provided . The work is presented in a unified way based on a few basic facts from qualitative theory of elliptic equations.