Counting points on Hessenberg varieties over finite fields

We give a counting formula in terms of modified Hall–Littlewood polynomials and the chromatic quasisymmetric function for the number of points on an arbitrary Hessenberg variety over a finite field. As a consequence, we express the Poincaré polynomials of complex Hessenberg varieties in terms of a Hall scalar product involving the symmetric functions above. We use these results to give a new proof of a combinatorial formula for the modified Hall–Littlewood polynomials.

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Publication Details

Journal
Algebraic Combinatorics
Published
2026-10-27
DOI
https://doi.org/10.5802/alco.519
Primary Topic
Advanced Combinatorial Mathematics
Type
article
Field-Weighted Citation Impact
0.00

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article

Counting points on Hessenberg varieties over finite fields

Samrith Ram, Antonio Nigro, Alex Abreu
Algebraic Combinatorics
Advanced Combinatorial Mathematics
article

Counting points on Hessenberg varieties over finite fields

Samrith Ram, Antonio Nigro, Alex Abreu
article en

Abstract

We give a counting formula in terms of modified Hall–Littlewood polynomials and the chromatic quasisymmetric function for the number of points on an arbitrary Hessenberg variety over a finite field. As a consequence, we express the Poincaré polynomials of complex Hessenberg varieties in terms of a Hall scalar product involving the symmetric functions above. We use these results to give a new proof of a combinatorial formula for the modified Hall–Littlewood polynomials.

Algebraic CombinatoricsVol. 9(5)
Indraprastha Institute of Information Technology Delhi (IN), Universidade Federal Fluminense (BR)
Department of Science and Technology, Ministry of Science and Technology, India, Conselho Nacional de Desenvolvimento Científico e Tecnológico, Russian Science Foundation
Openalex Percentile: Top 91%
Advanced Combinatorial Mathematics
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