In this paper, we formulate a "Grassmann extension" scheme for constructing noncommutative (Grassmann) extensions of Yang-Baxter maps together with their associated systems of P∆Es, based on the ideas presented in [11]. Using this scheme, we first construct a Grassmann extension of a Yang-Baxter map which constitutes a lift of a lattice Boussinesq system. The Grassmann-extended Yang-Baxter map can be squeezed down to a novel, integrable, Grassmann lattice Boussinesq system, and we derive its 3D-consistent limit. We show that some systems retain their 3D-consistency property in their Grassmann extension.
The formulation of the ideas presented in [11] into a Grassmann extension scheme;2. The derivation of a new Boussinesq-type Yang-Baxter map together with its Grassmann extension;3. The construction of an integrable, noncommutative (Grassmann) extension of a discrete Boussinesq system and its 3D-consistent limit. The latter gives rise to the following important point.4. We show that, for some systems, the 3D-consistency property does not break in their noncommutative extension.The paper is organised as follows: The next section provides with preliminary knowledge, essential for the text to be self-contained. In particular, we fix the notation we use throughout the text, and we give the basic definitions of systems on quad-graphs and Yang-Baxter maps. Furthermore, we demonstrate the relation between the former and the latter and the relation between the 3D consistency property and the Yang-Baxter equation. We also explain what a Lax representation is for both equations on quad graphs and Yang-Baxter maps. Finally, we present the basic steps of a simple scheme for constructing Grassmann extensions of discrete integrable systems and their associated Yang-Baxter maps; the related ideas were presented in [11]. In section 3, we apply the aforementioned scheme to system (1). Specifically, we consider the associated Yang-Baxter lift of (1), for which we construct a Grassmann extension. Then, we show that the latter can be squeezed down to a novel integrable system of lattice equations which can be considered as the Grassmann extension of system (1). Finally, in section 4, we present a Boussinesq-type system associated via a conservation law to the one obtained in section 3, and we prove the integrability-in the sense of 3D-consistency-for a limit of this system. Finally, the last section deals with some concluding remarks and thoughts for future work.
Preliminaries
NotationHere, we explain the notation we shall be using throughout the text.