On any set X may be defined the free algebra R〈X〉 (respectively, free commutative algebra R[X]) with coefficients in a ring R. It may also be equivalently described as the algebra of the free monoid X∗ (respectively, free commutative monoid M (X)). Furthermore, the algebra of differential polynomials R{X} with variables inX may be constructed. The main objective of this contribution is to provi...

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For any commutative algebra R the shuffle product on the tensor module T (R) can be deformed to a new product. It is called the quasi-shuffle algebra, or stuffle algebra, and denoted T q (R). We show that if R is the polynomial algebra, then T q (R) is free for some algebraic structure called Commutative TriDendriform (CTD-algebras). This result is part of a structure theorem for CTD-bialgebras...