On the Number of Periodic Orbits to Odd Order Differential Delay Systems

Abstract

In this paper, we study the periodic orbits of a type of odd order differential delay system with 2k−1 lags via the S1 index theory and the variational method. This type of system has not been studied by others. Our results provide a new and more accurate method for counting the number of periodic orbits.

Keywords

• odd order differential delay system
• periodic orbits
• critical point theory
• variational method