TY - JOUR AU - Aizicovici, Sergiu AU - Papageorgiou, Nikolaos S. AU - Staicu, Vasile PY - 2010/04/23 Y2 - 2024/03/28 TI - Existence and multiplicity of solutions for resonant nonlinear Neumann problems JF - Topological Methods in Nonlinear Analysis JA - TMNA VL - 35 IS - 2 SE - DO - UR - https://apcz.umk.pl/TMNA/article/view/TMNA.2010.014 SP - 235 - 252 AB - We consider nonlinear Neumann problems driven by the $p$-Laplaciandifferential operator with a Caratheodory nonlinearity. Under hypotheses whichallow resonance with respect to the principal eigenvalue $\lambda_{0}$ $=0$ at$\pm\infty$, we prove existence and multiplicity results. Our approach isvariational and uses critical point theory and Morse theory (critical groups). ER -