Characterizations of second-order differential operators

Włodzimierz Fechner, Eszter Gselmann, Aleksandra ŚwiÄ tczak

{Let $N,k$ be positive integers with $k\ge 2$, and $\hat{I}\text{c◯}\subset {\mathbb{R}}^N$ be a domain.} By the well-known properties of the Laplacian and the gradient, we have \[ Δ(f\cdot g…