Consider the equation $-\Delta u = f$ in a bounded domain $\Omega\subset\mathbb R^3$ with BC $u|_\Gamma=0$.
Let $f \in L^\infty$. Is it true that the weak solution $u \in L^\infty$?
Consider the equation $-\Delta u = f$ in a bounded domain $\Omega\subset\mathbb R^3$ with BC $u|_\Gamma=0$.
Let $f \in L^\infty$. Is it true that the weak solution $u \in L^\infty$?
Copyright © 2021 JogjaFile Inc.
Yes. The proof is based on a version of the weak maximum principle that is valid for weak solutions. See, for example, Theorem 8.1 in Gilbarg and Trudinger.