Restriction of characters to subgroups of wreath products and basic sets for the symmetric group

Abstract

In this paper, we give the decomposition into irreducible characters of the restriction to the wreath product ${\mathbb{Z}}_{p-1}\wr {\mathfrak{S}}_w$ of any irreducible character of $({\mathbb{Z}}_p⋊{\mathbb{Z}}_{p-1})\wr {\mathfrak{S}}_w$, where $p$ is any odd prime, $w\ge 0$ is an integer, and ${\mathbb{Z}}_p$ and ${\mathbb{Z}}_{p-1}$ denote the cyclic groups of order $p$ and $p-1$ respectively. This answers the question of how to decompose the restrictions to $p$-regular elements of irreducible characters of the symmetric group ${\mathfrak{S}}_n$ in the $\mathbb{Z}$-basis corresponding to the $p$-basic set of ${\mathfrak{S}}_n$ described by Brunat and Gramain in [1]. The result is given in terms of the Littlewood-Richardson coefficients for the symmetric group.