Multiplicity of periodic solutions for systems of weakly coupled parametrized second order differential equations

2noWe prove a multiplicity result of periodic solutions for a system of second order differential equations having asymmetric nonlinearities. The proof is based on a recent generalization of the Poincaré–Birkhoff fixed point theorem provided by Fonda and Ureña.partially_openopenCalamai, Alessandro; Sfecci, Andrea*Calamai, Alessandro; Sfecci, Andre