Enumerating Matroids and Linear Spaces

We show that the number of linear spaces on a set of $n$ points and the number of rank-3 matroids on a ground set of size $n$ are both of the form $(cn+o(n))^{n^2/6}$, where $c=e^{\sqrt{3}/2-3}(1+\sqrt{3})/2$. This is the final piece of the puzzle for enumerating fixed-rank matroids at this level of...

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Main Authors: Kwan, Matthew, Sah, Ashwin, Sawhney, Mehtaab
Format: Article
Language:English
Published: Académie des sciences 2023-02-01
Series:Comptes Rendus. Mathématique
Online Access:https://comptes-rendus.academie-sciences.fr/mathematique/articles/10.5802/crmath.423/
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author Kwan, Matthew
Sah, Ashwin
Sawhney, Mehtaab
author_facet Kwan, Matthew
Sah, Ashwin
Sawhney, Mehtaab
author_sort Kwan, Matthew
collection DOAJ
description We show that the number of linear spaces on a set of $n$ points and the number of rank-3 matroids on a ground set of size $n$ are both of the form $(cn+o(n))^{n^2/6}$, where $c=e^{\sqrt{3}/2-3}(1+\sqrt{3})/2$. This is the final piece of the puzzle for enumerating fixed-rank matroids at this level of accuracy: there are exact formulas for enumeration of rank-1 and rank-2 matroids, and it was recently proved by van der Hofstad, Pendavingh, and van der Pol that for constant $r\ge 4$ there are $(e^{1-r}n+o(n))^{n^{r-1}/r!}$ rank-$r$ matroids on a ground set of size $n$.
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spelling doaj-art-167138ee6c0a42da98a433d2544332d42025-02-07T11:06:37ZengAcadémie des sciencesComptes Rendus. Mathématique1778-35692023-02-01361G256557510.5802/crmath.42310.5802/crmath.423Enumerating Matroids and Linear SpacesKwan, Matthew0Sah, Ashwin1Sawhney, Mehtaab2Institute of Science and Technology Austria, 3400 Klosterneuburg, AustriaDepartment of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139, USADepartment of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139, USAWe show that the number of linear spaces on a set of $n$ points and the number of rank-3 matroids on a ground set of size $n$ are both of the form $(cn+o(n))^{n^2/6}$, where $c=e^{\sqrt{3}/2-3}(1+\sqrt{3})/2$. This is the final piece of the puzzle for enumerating fixed-rank matroids at this level of accuracy: there are exact formulas for enumeration of rank-1 and rank-2 matroids, and it was recently proved by van der Hofstad, Pendavingh, and van der Pol that for constant $r\ge 4$ there are $(e^{1-r}n+o(n))^{n^{r-1}/r!}$ rank-$r$ matroids on a ground set of size $n$.https://comptes-rendus.academie-sciences.fr/mathematique/articles/10.5802/crmath.423/
spellingShingle Kwan, Matthew
Sah, Ashwin
Sawhney, Mehtaab
Enumerating Matroids and Linear Spaces
Comptes Rendus. Mathématique
title Enumerating Matroids and Linear Spaces
title_full Enumerating Matroids and Linear Spaces
title_fullStr Enumerating Matroids and Linear Spaces
title_full_unstemmed Enumerating Matroids and Linear Spaces
title_short Enumerating Matroids and Linear Spaces
title_sort enumerating matroids and linear spaces
url https://comptes-rendus.academie-sciences.fr/mathematique/articles/10.5802/crmath.423/
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