Boundary Value Problems
Volume 2006 (2006), Article ID 25104, 9 pages
doi:10.1155/BVP/2006/25104

Periodic solutions of second-order nonautonomous dynamical systems

Abstract

We study the existence of periodic solutions for second-order nonautonomous dynamical systems. We give four sets of hypotheses which guarantee the existence of solutions. We were able to weaken the hypotheses considerably from those used previously for such systems. We employ a new saddle point theorem using linking methods.