Multiplicity of periodic orbits for a class of second order Hamiltonian systems with superlinear and sublinear nonlinearity

This paper is concerned with a class of second order Hamiltonian systems with superlinear and sublinear nonlinearity(P)where b(t) is a real function defined on 0, T], μ > 2 and H : 0, T] × R^N → R is a Carathéodory function. Some new multiplicity results of periodic orbits for the problem (P) are obtained via some critical point theorems.