Quasi-concavity for semilinear elliptic equations with non-monotone and anisotropic nonlinearities
Antonio M. Greco · Boundary Value Problems · 2006
A boundary-value problem for a semilinear elliptic equation in a convex ring is considered. Under suitable structural conditions, any classical solution lying between its (constant) boundary values is shown to decrease along each ray starting from the origin, and to have convex level surfaces.