Veronese subalgebras and Veronese morphisms for a class of Yang-Baxter algebras

Abstract

We study $d$-Veronese subalgebras $A^{(d)}$ of Yang-Baxter algebras $A_X= A(K, X, r)$ related to finite nondegenerate involutive set-theoretic solutions $(X, r)$ of the Yang-Baxter equation, where $K$ is a field and $d\geq 2$ is an integer. We find an explicit presentation of the $d$-Veronese $A^{(d)}$ in terms of one-generators and quadratic relations. We introduce the notion of a $d$-Veronese solution $(Y, r_Y)$, canonically associated to $(X,r)$ and use its Yang-Baxter algebra $A_Y= A(K, Y, r_Y)$ to define a Veronese morphism $v_{n,d}:A_Y \rightarrow A_X $. We prove that the image of $v_{n,d}$ is the $d$-Veronese subalgebra $A^{(d)}$, and find explicitly a minimal set of generators for its kernel. The results agree with their classical analogues in the commutative case. We show that the Yang-Baxter algebra $A(K, X, r)$ is a PBW algebra if and only if $(X,r)$ is a square-free solution. In this case the $d$-Veronese $A^{(d)}$ is also a PBW algebra.