Lie Rota--Baxter operators on the Sweedler algebra $H_4$

Abstract

If $A$ is an associative algebra, then we can define the adjoint Lie algebra $A^{(-)}$ and Jordan algebra $A^{(+)}$. It is easy to see that any associative Rota--Baxter operator on $A$ induces a Lie and Jordan Rota--Baxter operator on $A^{(-)}$ and $A^{(+)}$ respectively. Are there Lie (Jordan) Rota--Baxter operators, which are not associative Rota--Baxter operators? In the present article we are studying these questions for the Sweedler algebra $H_4$, that is a 4-dimension non-commutative Hopf algebra. More precisely, we describe the Rota--Baxter operators on Lie algebra on the adjoint Lie algebra $H_4^{(-)}$.