Infinitely many conservation laws for the discrete KdV equation

Abstract

In \cite{RH3} Rasin and Hydon suggested a way to construct an infinite number of conservation laws for the discrete KdV equation (dKdV), by repeated application of a certain symmetry to a known conservation law. It was not decided, however, whether the resulting conservation laws were distinct and nontrivial. In this paper we obtain the following results: (1) We give an alternative method to construct an infinite number of conservation laws using a discrete version of the Gardner transformation. (2) We give a direct proof that the Rasin-Hydon conservation laws are indeed distinct and nontrivial. (3) We consider a continuum limit in which the dKdV equation becomes a first-order eikonal equation. In this limit the two sets of conservation laws become the same, and are evidently distinct and nontrivial. This proves the nontriviality of the conservation laws constructed by the Gardner method, and gives an alternate proof of the nontriviality of the conservation laws constructed by the Rasin-Hydon method.

References in corpus (6)

• Classification of integrable equations on quad-graphs. The consistency approach
• Symmetries of Discrete Systems
• Backlund transformations for integrable lattice equations
• An integrable discretization of KdV at large times
• A discrete Schrodinger spectral problem and associated evolution equations
• Loop Groups and Discrete KdV Equations

Cited by in corpus (7)

• Recursion operators, conservation laws and integrability conditions for difference equations
• The Gardner method for symmetries
• Symmetry algebra of discrete KdV equations and corresponding differential-difference equations of Volterra type
• Infinitely many symmetries and conservation laws for quad-graph equations via the Gardner method
• Deriving conservation laws for ABS lattice equations from Lax pairs
• Conservation laws of some lattice equations
• Self-adjointness and conservation laws of difference equations