Through variational methods, we study nonautonomous systems of second-order ordinary differential equations with periodic boundary conditions. First, we deal with a nonlinear system, depending on a function , and prove that the set of bifurcation points for the solutions of the system is not -compact. Then, we deal with a linear system depending on a real parameter and on a function , and prove that there exists such that the set of the functions , such that the system admits nontrivial solutions, contains an accumulation point.
"Bifurcation for Second-Order Hamiltonian Systems with Periodic Boundary Conditions." Abstr. Appl. Anal. 2008 1 - 13, 2008. https://doi.org/10.1155/2008/756934