On Hopf's Lemma for sign-changing supersolutions to fractional Laplacian equations

Azahara DelaTorre, Enea Parini

In this paper we investigate the validity of Hopf's Lemma for a (possibly sign-changing) function $u\in H_0^s(\Omega )$ satisfying \[ (-Δ)^s u(x) \geq c(x)u(x) \quad \text{in }Ω,\] wher…