Radial symmetry of solutions to diffusion equations with discontinuous nonlinearities

We prove a radial symmetry result for bounded nonnegative solutions to the p-Laplacian semilinear equation −Δpu=f(u) posed in a ball of Rn and involving discontinuous nonlinearities f. When p=2 we obtain a new result which holds in every dimension n for certain positive discontinuous f. When p⩾n we prove radial symmetry for every locally bounded nonnegative f. Our approach is an extension of a method of P.L. Lions for the case p=n=2. It leads to radial symmetry combining the isoperimetric inequality and the Pohozaev identity.