Abstract

We derive a closed formula for the tensor product of a family of mixed tensors using Deligne’s interpolating category underline {Rep}(GL_{0}). We use this formula to compute the tensor product of a family of irreducible GL(n|n)-representations. This includes the tensor product of any two maximal atypical irreducible representations of GL(2|2).

Highlights

  • For the classical group GL(n) the tensor product decomposition L(λ) ⊗ L(μ) = cλνμL(ν)ν between two irreducible representations is given by the Littlewood-Richardson rule for the Littlewood-Richardson coefficients cλνμ

  • A classical result from Berele and Regev [1] and Sergeev [21] shows that the fusion rule between direct summands of tensor powers V ⊗r of the standard representation V km|n is again given by the Littlewood-Richardson rule

  • Since the decomposition of the tensor product of two indecomposable elements is known for Rep(GLm−n) by results of Comes and Wilson [7], we obtain an analogous decomposition law once we describe the image Fm|n(X) of an arbitrary indecomposable object X in Rep(GLm−n). This was achieved in [13] based on results by Brundan and Stroppel [6] on the interplay between Khovanov algebras and Walled Brauer algebras

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Summary

Introduction

Since the decomposition of the tensor product of two indecomposable elements is known for Rep(GLm−n) by results of Comes and Wilson [7], we obtain an analogous decomposition law once we describe the image Fm|n(X) of an arbitrary indecomposable object X in Rep(GLm−n). This was achieved in [13] based on results by Brundan and Stroppel [6] on the interplay between Khovanov algebras and Walled Brauer algebras. [13], these results give a decomposition law for their tensor products, covering in particular the decomposition between any two irreducible GL(m|1)-representations

The Main Results
Summary of the Proof
Step 1
Step 2
Step 3
Step 4
Step 5
Step 6
Representations
The Category Rn
Atypicality
Indecomposable Representations and Combinatorics of Bipartitions
Deligne’s Interpolating Category
The Symmetric and Alternating Powers
The Lifting Map
Generic Tensor Product Decomposition
Computations in Rt
The R2-Case
The Duflo-Serganova Functor DS
Clean Decomposition
Nonvanishing Superdimension
The Lower Atypical Summands in Rn
Full Text
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