Difference systems in bond and face variables and non-potential versions of discrete integrable systems

Abstract

Integrable discrete scalar equations defined on a~two or a three dimensional lattice can be rewritten as difference systems in bond variables or in face variables respectively. Both the difference systems in bond variables and the difference systems in face variables can be regarded as vector versions of the original equations. As a result, we link some of the discrete equations by difference substitutions and reveal the non-potential versions of some consistent-around-the-cube equations. We obtain higher-point configurations, including pairs of compatible six~points equations on the ${\mathbb Z}^2$ lattice together with associated seven points equations. Also we obtain a variety of compatible ten point equations together with associated ten and twelve point equations on the ${\mathbb Z}^3$ lattice. Finally, we present integrable multiquadratic quad relations.