Monomial Rota—Baxter operators on free commutative non-unital algebra

A Rota—Baxter operator defined on the polynomial algebra is called monomial if it maps each monomial to a monomial with some coefficient. We classify monomial Rota—Baxter operators defined on the algebra of polynomials in one variable with no constant term. We also describe injective monomial Rota—Baxter operators of nonzero weight on the algebra of polynomials in several variables with no constant term.