Recent progress on second-order elliptic and parabolic equations in double divergence form
Seick Kim
TL;DR
The paper surveys recent advances in second-order elliptic equations in double divergence form and their parabolic counterparts, focusing on existence, regularity, and quantitative estimates under structured coefficient classes. It develops a coherent regularity theory using the transposition method, $\mathrm{DMO}$/Morrey-type conditions, and associated modulus of continuity to obtain continuity, higher integrability, and Harnack inequalities, including extensions to lower-order terms. Key contributions include sharp weak-solution frameworks, higher integrability under $\mathrm{DMO}$, global continuity results, and parabolic analogues with corresponding Harnack principles, enabling Green's-function-type bounds and robust boundary behavior. The results significantly broaden the PDE toolbox for double divergence operators, enabling finer qualitative understanding in non-smooth settings and across elliptic and parabolic regimes, with potential applications to diffusion processes and invariant measures.
Abstract
This article presents a comprehensive overview and supplement to recent developments in second-order elliptic partial differential equations formulated in double divergence form, along with an exploration of their parabolic counterparts.
