A characterization of socular highest weight modules and Richardson orbits of classical types

TL;DR

This paper characterizes socular highest weight modules in classical Lie algebras using Young tableaux and introduces Z-diagrams to describe associated Richardson orbits, providing explicit criteria for integral and nonintegral cases.

Contribution

It provides an explicit characterization of socular modules via Young tableaux and Z-diagrams, linking module properties to Richardson orbit partitions.

Findings

Characterization of socular modules using Young tableaux for integral cases

Extension of characterization to nonintegral cases

Description of Richardson orbit partitions via Z-diagrams

Abstract

Let $\mathfrak{g}$ be a simple complex Lie algebra of classical type with a Cartan subalgebra $\mathfrak{h}$. We fix a standard parabolic subalgebra $\mathfrak{p}\supset \mathfrak{h}$. The socular simple modules are just those highest weight modules with largest possible Gelfand-Kirillov dimension in the corresponding parabolic category $\mathcal{O}^{\mathfrak{p}}$. In this article, we will give an explicit characterization for these modules. When the module is integral, our characterization is given by the information of the corresponding Young tableau associated to the given highest weight module. When the module is nonintegral, we still have some characterization by using the results in the integral case. In our characterization, we define a particular Young diagram called Z-diagram. From this diagram, we can describe the partition type of the unique Richardson orbit associated to the given parabolic subalgebra $\mathfrak{p}$.