$q$-Rationals and Finite Schubert Varieties

The classical $q$-analogue of the integers was recently generalized by Morier-Genoud and Ovsienko to give $q$-analogues of rational numbers. Some combinatorial interpretations are already known, namely as the rank generating functions for certain partially ordered sets. We give a new interpretation,...

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Main Author: Ovenhouse, Nicholas
Format: Article
Language:English
Published: Académie des sciences 2023-05-01
Series:Comptes Rendus. Mathématique
Online Access:https://comptes-rendus.academie-sciences.fr/mathematique/articles/10.5802/crmath.446/
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author Ovenhouse, Nicholas
author_facet Ovenhouse, Nicholas
author_sort Ovenhouse, Nicholas
collection DOAJ
description The classical $q$-analogue of the integers was recently generalized by Morier-Genoud and Ovsienko to give $q$-analogues of rational numbers. Some combinatorial interpretations are already known, namely as the rank generating functions for certain partially ordered sets. We give a new interpretation, showing that the numerators of $q$-rationals count the sizes of certain varieties over finite fields, which are unions of open Schubert cells in some Grassmannian.
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spelling doaj-art-fd33967822f942e18464f0bc5196438b2025-02-07T11:07:37ZengAcadémie des sciencesComptes Rendus. Mathématique1778-35692023-05-01361G480781810.5802/crmath.44610.5802/crmath.446$q$-Rationals and Finite Schubert VarietiesOvenhouse, Nicholas0Department of Mathematics, Yale University, 10 Hillhouse Ave, New Haven CT, USAThe classical $q$-analogue of the integers was recently generalized by Morier-Genoud and Ovsienko to give $q$-analogues of rational numbers. Some combinatorial interpretations are already known, namely as the rank generating functions for certain partially ordered sets. We give a new interpretation, showing that the numerators of $q$-rationals count the sizes of certain varieties over finite fields, which are unions of open Schubert cells in some Grassmannian.https://comptes-rendus.academie-sciences.fr/mathematique/articles/10.5802/crmath.446/
spellingShingle Ovenhouse, Nicholas
$q$-Rationals and Finite Schubert Varieties
Comptes Rendus. Mathématique
title $q$-Rationals and Finite Schubert Varieties
title_full $q$-Rationals and Finite Schubert Varieties
title_fullStr $q$-Rationals and Finite Schubert Varieties
title_full_unstemmed $q$-Rationals and Finite Schubert Varieties
title_short $q$-Rationals and Finite Schubert Varieties
title_sort q rationals and finite schubert varieties
url https://comptes-rendus.academie-sciences.fr/mathematique/articles/10.5802/crmath.446/
work_keys_str_mv AT ovenhousenicholas qrationalsandfiniteschubertvarieties