On the integrability of a lattice equation with two continuum limits

Abstract

We study a new example of lattice equation being one of the key equations of a recent generalized symmetry classification of five-point differential-difference equations. This equation has two different continuum limits which are the well-known fifth order partial-differential equations, namely, the Sawada-Kotera and Kaup-Kupershmidt equations. We justify its integrability by constructing an $L-A$ pair and a hierarchy of conservation laws.