Quasisymmetric Schur $Q$-functions and peak Young quasisymmetric Schur functions

Abstract

In this paper, we explore the relationship between quasisymmetric Schur $Q$-functions and peak Young quasisymmetric Schur functions. We introduce a bijection on $\mathsf{SPIT}(α)$ such that $\{\mathrm{w}_{\rm c}(T) \mid T \in \mathsf{SPIT}(α)\}$ and $\{\mathrm{w}_{\rm r}(T) \mid T \in \mathsf{SPIT}(α)\}$ share identical descent distributions. Here, $\mathsf{SPIT}(α)$ is the set of standard peak immaculate tableaux of shape $α$, and $\mathrm{w}_{\rm c}$ and $\mathrm{w}_{\rm r}$ denote column reading and row reading, respectively. By combining this equidistribution with the algorithm developed by Allen, Hallam, and Mason, we demonstrate that the transition matrix from the basis of quasisymmetric Schur $Q$-functions to the basis of peak Young quasisymmetric Schur functions is upper triangular, with entries being non-negative integers. Furthermore, we provide explicit descriptions of the expansion of peak Young quasisymmetric Schur functions in specific cases, in terms of quasisymmetric Schur $Q$-functions. We also investigate the combinatorial properties of standard peak immaculate tableaux, standard Young composition tableaux, and standard peak Young composition tableaux. We provide a hook length formula for $\mathsf{SPIT}(α)$ and show that standard Young composition tableaux and standard peak Young composition tableaux can be bijectively mapped to specific words in a familiar form. Especially, cases of compositions with rectangular shape are examined in detail.