On quasisymmetric power sums

Abstract

In the 1995 paper entitled “Noncommutative symmetric functions”, Gelfand et al. defined two noncommutative symmetric function analogues for the power sum basis of the symmetric functions. This paper explores the combinatorial properties of their duals, two distinct quasisymmetric power sum bases. In contrast to the symmetric power sums, the quasisymmetric power sums have a more complex combinatorial description. This paper offers a first detailed exploration of these two relatively unstudied quasisymmetric bases, in which we show that they refine the classical symmetric power sum basis, we give transition matrices to other well-understood bases, and we provide explicit formulas for products of quasisymmetric power sums.