Enumerating Matroids and Linear Spaces

Autor: Kwan, Matthew, Sah, Ashwin, Sawhney, Mehtaab
Jazyk: English<br />French
Rok vydání: 2023
Předmět:
Zdroj: Comptes Rendus. Mathématique, Vol 361, Iss G2, Pp 565-575 (2023)
Druh dokumentu: article
ISSN: 1778-3569
DOI: 10.5802/crmath.423
Popis: 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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