Involutive latin solutions of the Yang-Baxter equation

TL;DR

This paper explores involutive latin solutions to the Yang-Baxter equation by characterizing associated algebraic structures called rumples, classifying affine solutions, and developing extension theory to find non-affine examples.

Contribution

It introduces the concept of latin rumples, characterizes affine solutions via prime factorization, and develops extension theory for non-affine solutions.

Findings

Affine latin rumples exist for orders with specific prime factorizations.

A class of solutions derived from near-circulant matrices satisfying certain commutation relations.

Generators of the displacement group have order dividing four in certain solutions.

Abstract

Wolfgang Rump showed that there is a one-to-one correspondence between nondegenerate involutive set-theoretic solutions of the Yang-Baxter equation and binary algebras in which all left translations $L_x$ are bijections, the squaring map is a bijection, and the identity $(xy)(xz) = (yx)(yz)$ holds. We call these algebras \emph{rumples} in analogy with quandles, another class of binary algebras giving solutions of the Yang-Baxter equation. We focus on latin rumples, that is, on rumples in which all right translations are bijections as well. We prove that an affine latin rumple of order $n$ exists if and only if $n=p_1^{p_1 k_1}\cdots p_m^{p_m k_m}$ for some distinct primes $p_i$ and positive integers $k_i$. A large class of affine solutions is obtained from nonsingular near-circulant matrices $A$, $B$ satisfying $[A,B]=A^2$. We characterize affine latin rumples as those latin rumples for which the displacement group generated by $L_x L_y\inv$ is abelian and normal in the group generated by all translations. We develop the extension theory of rumples sufficiently to obtain examples of latin rumples that are not affine, not even isotopic to a group. Finally, we investigate latin rumples in which the dual identity $(zx)(yx) = (zy)(xy)$ holds as well, and we show, among other results, that the generators $L_x L_y\inv$ of their displacement group have order dividing four.