We study the problem of existence and multiplicity of subharmonic solutions for a second order nonlinear ODE in presence of lower and upper solutions. We show how such additional information can be used to obtain more precise multiplicity results. Applications are given to pendulum type equations and to Ambrosetti-Prodi results for parameter dependent equations.

%B Discrete & Continuous Dynamical Systems - A %V 33 %P 89 %G eng %U http://aimsciences.org//article/id/3638a93e-4f3e-4146-a927-3e8a64e6863f %R 10.3934/dcds.2013.33.89 %0 Journal Article %J Advanced Nonlinear Studies %D 2011 %T Subharmonic solutions of planar Hamiltonian systems: a rotation number approach %A Alberto Boscaggin %B Advanced Nonlinear Studies %I Advanced Nonlinear Studies, Inc. %V 11 %P 77–103 %G eng %R 10.1515/ans-2011-0104 %0 Journal Article %J Le Matematiche %D 2011 %T Subharmonic solutions of planar Hamiltonian systems via the Poincaré́-Birkhoff theorem %A Alberto Boscaggin %XWe revisit some recent results obtained in [1] about the existence of subharmonic solutions for a class of (nonautonomous) planar Hamiltonian systems, and we compare them with the existing literature. New applications to undamped second order equations are discussed, as well.

%B Le Matematiche %V 66 %P 115–122 %G eng