1. CMB 2009 (vol 53 pp. 347)
||Multiple Nontrivial Solutions for Doubly Resonant Periodic Problems|
We consider semilinear periodic problems with the right-hand side nonlinearity satisfying a double resonance condition between two successive eigenvalues. Using a combination of variational and degree theoretic methods, we prove the existence of at least two nontrivial solutions.
Keywords:double resonance, generalized LL-condition, Leray-Schauder degree, Cerami condition