From NLS type matrix refactorisation problems to set-theoretical solutions of the 2- and 3-simplex equations
Sotiris Konstantinou-Rizos
TL;DR
The work tackles the construction of set-theoretical $n$-simplex maps by varying the spectral parameter in Lax (Darboux) matrices, producing hierarchies of Yang–Baxter and Zamolodchikov maps tied to Adler and NLS-type equations. The authors derive explicit Adler-type YB maps $Y_1$ and $Y_2$, NLS-type maps $Y_3$ and $Y_4$, derivative NLS-type maps $Y_5$ and $Y_6$, and a parametric Zamolodchikov tetrahedron map $T_{a,b,c}$, many of which come with integrals of motion. They prove Liouville integrability for at least two maps ($Y_1$ and $Y_6$) and establish invariant structures for others, demonstrating the viability of the spectral-parameter variation method for generating new integrable maps. The results extend prior work on Darboux-refactorisation and local simplex equations, offering a framework for noncommutative extensions and higher-simplex or polygon generalisations with potential applications in integrable systems theory.
Abstract
We present a method for constructing hierarchies of solutions to $n$-simplex equations by variating the spectral parameter in their Lax representation. We use this method to derive new solutions to the set-theoretical 2- and 3-simplex equations which are related to the Adler map and Nonlinear Schrödinger (NLS) type equations. Moreover, we prove that some of the derived Yang--Baxter maps are completely integrable.
