Advances in Difference Equations
Volume 2011 (2011), Article ID 806458, 15 pages
doi:10.1155/2011/806458
Research Article

Multiple Periodic Solutions for Difference Equations with Double Resonance at Infinity

Xiaosheng Zhang1 and Duo Wang2,3

1School of Mathematical Sciences, Capital Normal University, Beijing 100048, China
2School of Mathematical Sciences, Peking University, Beijing 100875, China
3School of Mathematical Sciences, South China Normal University, Guangzhou 510631, China

Received 6 November 2010; Accepted 19 January 2011

Academic Editor: John Graef

Copyright © 2011 Xiaosheng Zhang and Duo Wang. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

By using variational methods and Morse theory, we study the multiplicity of the periodic solutions for a class of difference equations with double resonance at infinity. To the best of our knowledge, investigations on double-resonant difference systems have not been seen in the literature.