Construction of Young modules and filtration multiplicities for Brauer algebras of type $C$

Abstract

In this paper, we construct the permutation modules and Young modules for Brauer algebras of type $C$ by extending the representation theory of the group algebra of hyperoctahedral groups. Additionally, we develop a stratifying system for Brauer algebras of type $C$, thereby extending the work of Hemmer-Nakano in \cite{HN} on Hecke algebras. This framework allows us to determine when the multiplicities of cell modules in any filtration are well-defined. As a result, we prove that if the characteristic of the field is neither $2$ nor $3$, then every permutation module of the Brauer algebra of type $C$ decomposes into a direct sum of indecomposable Young modules. We also establish certain cohomological criteria for the group algebra of the hyperoctahedral groups, which are necessary to prove the results for the Brauer algebras of type $C$.