Involutive latin solutions of the Yang-Baxter equation

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 ( x y ) ( x z ) = ( y x ) ( y z ) holds. We call these algebras 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 ⋯ 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 − 1 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 ( z x ) ( y x ) = ( z y ) ( x y ) holds as well, and we show, among other results, that the generators L x L y − 1 of their displacement group have order dividing four.