Elliptic soliton solutions of lattice eigenfunction equations of the KdV type

Abstract

It is known that some integrable lattice equations can be formulated by the eigenfunctions of the Lax triplet of the lattice potential Korteweg-de Vries (lpKdV) equation; the eigenfunctions satisfy a discrete Abel formula in which the `integration' constant defines the $δ$ parameter in some equations in the Adler-Bobenko-Suris (ABS) classification. In this paper, we present a full Darboux transformation for the Lax triplet of the lpKdV equation, and eigenfunctions are formulated in terms of Casoratians. When the eigenfunctions take the elementary discrete Lamé functions, we get the elliptic $N$-soliton solution for the lpKdV equation after $N$-fold Darboux transformation. We then determine the constant in the discrete Abel formula in this case. The eigenfunctions are used to formulate elliptic $N$-soliton solutions for various equations in the ABS list, such as H3($δ$), $Q1(Δ)$, Q2 and Q3($Δ$) equations.