Picone-type inequalities for nonlinear elliptic equations and their applications.
We prove pointwise gradient bounds for entire solutions of pde’s of the form ℒu(x) = ψ(x, u(x), ∇u(x)), where ℒ is an elliptic operator (possibly singular or degenerate). Thus, we obtain some Liouville type rigidity results. Some classical results of J. Serrin are also recovered as particular cases of our approach.
We study the existence and nonexistence of positive solutions of the nonlinear equation where , , is a regular bounded open domain in and the -Laplacian is introduced for a continuous function defined on . The positive parameter induces the bifurcation phenomena. The study of the equation (Q) needs generalized Lebesgue and Sobolev spaces. In this paper, under suitable assumptions, we show that some variational methods still work. We use them to prove the existence of positive solutions...