On the solvability of the discrete nonlinear Schrodinger equation with subcubic potential

Abstract

In this paper, we analyze the solvability of the discrete nonlinear Schrödinger equation \begin{equation*} iβ(Δ_t+\nabla_t)ϕ(t,k) +γ|ϕ(t,k)|^2ϕ(t,k) +\varepsilon Δ_k^2ϕ(t,k-1) = g(t,ϕ(t,k)), \end{equation*} where ${\Delta }_t$ and ${\Delta }_k$ denote the standard forward difference operators in the variables $t$ and $k$, respectively, ${\nabla }_t$ denotes the standard backward difference operator in $t$, and \begin{equation*} Δ_k^2ϕ(t,k-1) = ϕ(t,k+1)-2ϕ(t,k)+ϕ(t,k-1) \end{equation*} is the discrete Laplacian operator in the spatial variable $k$. Throughout, we will assume the parameters $\beta$ and $\epsilon$ are positive real numbers, the parameter $\gamma$ is a nonzero real number, and the potential function $g:\mathbb{Z}\times \mathbb{C}\to \mathbb{C}$ is continuous.