Infinitely many stationary solutions of discrete vector nonlinear Schrodinger equation with symmetry

In this paper we study the existence of stationary solutions for the following discrete vector nonlinear Schrodinger equation i partial derivative phi(n)/partial derivative(t) = -Lambda phi(n) + tau(n)phi(n) - if(n, vertical bar phi(n)vertical bar)phi(n), where phi(n) is a sequence of 2-component vector, i = (0 1 1 0), Delta phi(n) = phi(n+1) + phi(n-1) - 2 phi(n) is the discrete Laplacian in one spatial dimension and sequence tau(n) is assumed to be N-periodic in n, i.e. tau(n+N) = tau(n). We prove the existence of infinitely many nontrivial stationary solutions for this system by variational methods. The same method can also be applied to obtain infinitely many breather solutions for single discrete nonlinear Schrodinger equation. (C) 2009 Elsevier Inc. All rights reserved.