Existence theorems of periodic solutions for fourth-order nonlinear functional difference equations
By using of the critical point method, the existence of periodic solutions for fourth-order nonlinear functional difference equations is obtained. The main approaches used in our paper are variational techniques and the Saddle Point Theorem. The problem is to solve the existence of periodic solutions of fourth-order nonlinear functional difference equations. Results obtained generalize and complement the existing one.
existence periodic solutions fourth-order functional difference equations discrete variational theory 39a11