On matrix Lax representations and constructions of Miura-type transformations for differential-difference equations

TL;DR

This paper investigates how gauge transformations can eliminate shifts in matrix Lax representations of differential-difference equations, leading to new integrable equations and transformations connecting known models.

Contribution

It provides criteria for eliminating shifts via gauge transformations and constructs new Lax representations and integrable equations related to known models.

Findings

Criteria for eliminating shifts in Lax representations using gauge transformations.

Construction of new integrable equations connected to known models.

Development of new Miura-type transformations linking different equations.

Abstract

This paper is part of a research project on relations between differential-difference matrix Lax representations (MLRs) with the action of gauge transformations and discrete Miura-type transformations (MTs) for (nonlinear) integrable differential-difference equations. The paper addresses the following problem: when and how can one eliminate some shifts of dependent variables from the discrete (difference) part of an MLR by means of gauge transformations? Using results on this problem, we present applications to constructing new MLRs and new integrable equations connected by new MTs to known equations. In particular, we obtain results of this kind for equations connected to the following ones: - The two-component Belov--Chaltikian lattice. - The equation (introduced by G. Mari Beffa and Jing Ping Wang) which describes the evolution induced on invariants by an invariant evolution of planar polygons. - An equation from [S. Igonin, arXiv:2405.08579] related to the Toda lattice in the Flaschka--Manakov coordinates.