Geometric categorifications of Verma modules: Grassmannian Quiver Hecke algebras

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Main Authors: Maksimau, Ruslan, Stroppel, Catharina
Format: Preprint
Published: 2024
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author Maksimau, Ruslan
Stroppel, Catharina
author_facet Maksimau, Ruslan
Stroppel, Catharina
contents Naisse and Vaz defined an extension of KLR algebras to categorify Verma modules. We realise these algebras geometrically as convolution algebras in Borel-Moore homology. For this we introduce Grassmannian-Steinberg quiver flag varieties. They generalize Steinberg quiver flag varieties in a non-obvious way, reflecting the diagrammatics from the Naisse-Vaz construction. Using different kind of stratifications we provide geometric explanations of the rather mysterious algebraic and diagrammatic basis theorems. A geometric categorification of Verma modules was recently found in the special case of $\mathfrak{sl}_2$ by Rouquier. Rouquier's construction uses coherent sheaves on certain quasi-map spaces to flag varieties (zastavas), whereas our construction is implicitly based on perverse sheaves. Both should be seen as parts (on dual sides) of a general geometric framework for the Naisse-Vaz approach. We first treat the (substantially easier) $\mathfrak{sl}_2$ case in detail and construct as a byproduct a geometric dg-model of the nil-Hecke algebras. The extra difficulties we encounter in general require the use of more complicated Grassmannian-Steinberg quiver flag varieties. Their definition arises from combinatorially defined diagram varieties which we assign to each Naisse-Vaz basis diagram. Our explicit analysis here might shed some light on categories of coherent sheaves on more general zastava spaces studied by Feigin-Finkelberg-Kuznetsov-Mirković and Braverman, which we expect to occur in a generalization of Rouquier's construction away from $\mathfrak{sl}_2$.
format Preprint
id arxiv_https___arxiv_org_abs_2405_20262
institution arXiv
publishDate 2024
record_format arxiv
spellingShingle Geometric categorifications of Verma modules: Grassmannian Quiver Hecke algebras
Maksimau, Ruslan
Stroppel, Catharina
Representation Theory
16S30, 17B10, 14M15, 20G05, 17B20, 55N25, 55N33
Naisse and Vaz defined an extension of KLR algebras to categorify Verma modules. We realise these algebras geometrically as convolution algebras in Borel-Moore homology. For this we introduce Grassmannian-Steinberg quiver flag varieties. They generalize Steinberg quiver flag varieties in a non-obvious way, reflecting the diagrammatics from the Naisse-Vaz construction. Using different kind of stratifications we provide geometric explanations of the rather mysterious algebraic and diagrammatic basis theorems. A geometric categorification of Verma modules was recently found in the special case of $\mathfrak{sl}_2$ by Rouquier. Rouquier's construction uses coherent sheaves on certain quasi-map spaces to flag varieties (zastavas), whereas our construction is implicitly based on perverse sheaves. Both should be seen as parts (on dual sides) of a general geometric framework for the Naisse-Vaz approach. We first treat the (substantially easier) $\mathfrak{sl}_2$ case in detail and construct as a byproduct a geometric dg-model of the nil-Hecke algebras. The extra difficulties we encounter in general require the use of more complicated Grassmannian-Steinberg quiver flag varieties. Their definition arises from combinatorially defined diagram varieties which we assign to each Naisse-Vaz basis diagram. Our explicit analysis here might shed some light on categories of coherent sheaves on more general zastava spaces studied by Feigin-Finkelberg-Kuznetsov-Mirković and Braverman, which we expect to occur in a generalization of Rouquier's construction away from $\mathfrak{sl}_2$.
title Geometric categorifications of Verma modules: Grassmannian Quiver Hecke algebras
topic Representation Theory
16S30, 17B10, 14M15, 20G05, 17B20, 55N25, 55N33
url https://arxiv.org/abs/2405.20262