Elliptic resonant problems at higher eigenvalues with an unbounded nonlinear term (Q1265116)

The authors consider elliptic resonant problems at higher eigenvalues with unbounded nonlinear term: \[ -\Delta u=\lambda_k u+g(x,u) \quad\text{in }\Omega,\qquad u=0 \quad\text{on }\partial\Omega. \] The proofs rely on the minimax method using the Saddle Point Theorem and a Generalised Mountain Pass Theorem.