Hasse-Schmidt Derivations and the Hopf Algebra of Non-Commutative Symmetric Functions

Abstract

Let NSymm be the Hopf algebra of non-commutative symmetric functions (in an infinity of indeterminates): . It is shown that an associative algebra A with a Hasse-Schmidt derivation ) on it is exactly the same as an NSymm module algebra. The primitives of NSymm act as ordinary derivations. There are many formulas for the generators in terms of the primitives (and vice-versa). This leads to formulas for the higher derivations in a Hasse-Schmidt derivation in terms of ordinary derivations, such as the known formulas of Heerema and Mirzavaziri (and also formulas for ordinary derivations in terms of the elements of a Hasse-Schmidt derivation). These formulas are over the rationals; no such formulas are possible over the integers. Many more formulas are derivable.

Keywords

• non-commutative symmetric functions
• Hasse-Schmidt derivation
• higher derivation
• Heerema formula
• Mirzavaziri formula
• non-commutative Newton formulas