Splitting the square of homogeneous and elementary functions into their symmetric and anti-symmetric parts

TL;DR

This paper analyzes the expansion of squares of homogeneous and elementary symmetric functions into Schur functions, introducing a sign statistic to distinguish symmetric and anti-symmetric parts using combinatorial tableau methods.

Contribution

It introduces a sign statistic on tableaux to identify contributions of Schur functions in plethysm decompositions of symmetric function squares.

Findings

Sign statistic determines plethysm contributions.

Decomposition into symmetric and anti-symmetric parts clarified.

Combinatorial tableau methods applied to plethysm analysis.

Abstract

We consider the expansion of the square of a complete homogeneous function $h_\lambda$, or of an elementary symmetric function $e_\lambda$, in the basis of Schur functions. This square also decomposes into two plethysms, $s_2[h_\lambda]$ and $s_{11}[h_\lambda]$ (resp. $s_2[h_\lambda]$ and $s_{11}[h_\lambda]$), which are called its symmetric and anti-symmetric parts, respectively. We define a sign statistic on the set of tableaux that index the Schur functions appearing in the square of those symmetric functions. This sign statistic allows to determine to which plethysm each Schur function contributes. We use mainly combinatorial tools on tableaux (product on tableau and RSK) and basic manipulations on plethysm and symmetric functions.