Multiple periodic solutions for superquadratic second-order discrete Hamiltonian systems
Abstract Some multiplicity results are obtained for periodic solutions of the nonautonomous superquadratic second-order discrete Hamiltonian systems Δ 2 u ( t - 1 ) + ∇ F ( t , u ( t ) ) = 0 ∀ t ∈ Z by using critical point theory, especially, a three critical points theorem proposed by Brezis and Nirenberg.