Multiplicity of solutions for semilinear variational inequalities via linking and ∇-theorems

Abstract

We prove the existence of three distinct nontrivial solutions for a class of semilinear elliptic variational inequalities involving a superlinear nonlinearity. The approach is variational and is based on linking and ∇-theorems. Some nonstandard adaptations are required to overcome the lack of the Palais–Smale condition.