• Medientyp: E-Artikel
  • Titel: Enumerating matroids and linear spaces
  • Beteiligte: Kwan, Matthew Alan [Verfasser:in]; Sah, Ashwin [Verfasser:in]; Sawhney, Mehtaab [Verfasser:in]
  • Erschienen: Academie des Sciences, 2023
  • Erschienen in: Kwan MA, Sah A, Sawhney M. Enumerating matroids and linear spaces. Comptes Rendus Mathematique . 2023;361(G2):565-575. doi: 10.5802/crmath.423
  • Sprache: Englisch
  • DOI: https://doi.org/10.5802/crmath.423
  • ISSN: 1631-073X; 1778-3569
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  • Beschreibung: 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))n2/6, where c=e3√/2−3(1+3–√)/2. This is the final piece of the puzzle for enumerating fixed-rank matroids at this level of accuracy: the numbers of rank-1 and rank-2 matroids on a ground set of size n have exact representations in terms of well-known combinatorial functions, and it was recently proved by van der Hofstad, Pendavingh, and van der Pol that for constant r≥4 there are (e1−rn+o(n))nr−1/r! rank-r matroids on a ground set of size n. In our proof, we introduce a new approach for bounding the number of clique decompositions of a complete graph, using quasirandomness instead of the so-called entropy method that is common in this area.
  • Zugangsstatus: Freier Zugang