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The Mayhew--Newman--Welsh--Whittle conjecture predicts that asymptotically almost all matroids are sparse paving. We study the gap between paving and sparse paving matroids at the logarithmic scale. Let \(p_n\) be the number of paving…

组合数学 · 数学 2026-05-13 Mohsen Aliabadi

Hlineny's Theorem shows that any sentence in the monadic second-order logic of matroids can be tested in polynomial time, when the input is limited to a class of F-representable matroids with bounded branch-width (where F is a finite…

组合数学 · 数学 2022-11-08 Daryl Funk , Dillon Mayhew , Mike Newman

Neighborly polytopes are those that maximize the number of faces in each dimension among all polytopes with the same number of vertices. Despite their extremal properties they form a surprisingly rich class of polytopes, which has been…

组合数学 · 数学 2015-01-30 Hiroyuki Miyata , Arnau Padrol

The family of 2-level matroids, that is, matroids whose base polytope is 2-level, has been recently studied and characterized by means of combinatorial properties. 2-level matroids generalize series-parallel graphs, which have been already…

组合数学 · 数学 2015-10-15 Francesco Grande , Juanjo Rué

It has been conjectured that asymptotically almost all matroids are sparse paving, i.e. that $s(n) \sim m(n)$, where $m(n)$ denotes the number of matroids on a fixed groundset of size $n$, and $s(n)$ the number of sparse paving matroids. In…

组合数学 · 数学 2016-01-26 Rudi Pendavingh , Jorn van der Pol

This article is a survey of matroid theory aimed at algebraic geometers. Matroids are combinatorial abstractions of linear subspaces and hyperplane arrangements. Not all matroids come from linear subspaces; those that do are said to be…

代数几何 · 数学 2014-09-12 Eric Katz

The notion of Ehrhart tensor polynomials, a natural generalization of the Ehrhart polynomial of a lattice polytope, was recently introduced by Ludwig and Silverstein. We initiate a study of their coefficients. In the vector and matrix…

组合数学 · 数学 2017-06-07 Sören Berg , Katharina Jochemko , Laura Silverstein

In earlier work in collaboration with Pavel Galashin and Thomas McConville we introduced a version of chip-firing for root systems. Our investigation of root system chip-firing led us to define certain polynomials analogous to Ehrhart…

组合数学 · 数学 2019-12-24 Sam Hopkins , Alexander Postnikov

In this paper we highlight some enumerative results concerning matroids of low rank and prove the tail-ends of various sequences involving the number of matroids on a finite set to be log-convex. We give a recursion for a new, slightly…

组合数学 · 数学 2007-05-23 W. M. B. Dukes

We characterize the quotients among lattice path matroids (LPMs) in terms of their diagrams. This characterization allows us to show that ordering LPMs by quotients yields a graded poset, whose rank polynomial has the Narayana numbers as…

组合数学 · 数学 2024-01-17 Carolina Benedetti , Kolja Knauer

The Ehrhart ring of the edge polytope $\mathcal{P}_G$ for a connected simple graph $G$ is known to coincide with the edge ring of the same graph if $G$ satisfies the odd cycle condition. This paper gives for a graph which does not satisfy…

组合数学 · 数学 2011-05-26 Tetsushi Matsui

We give explicit recursive constructions for the polytope of all matroids $\Omega_{r,n}$ in ranks 2 and 3 for all ground set sizes. This polytope was introduced in recent work by Ferroni and Fink as a tool for checking positivity…

组合数学 · 数学 2026-05-13 Narayan Collins , Victoria Schleis

There has been wide interest in understanding which properties of base graphs of matroids extend to base-cobase graphs of matroids. A significant result of Naddef and Pulleyblank (1984) shows that the $1$-skeleton of any $(0,1)$-polytope is…

组合数学 · 数学 2025-06-30 Leonardo Martínez-Sandoval , Kolja Knauer

We initiate the study of a type $C_n$ generalization of the lattice path matroids defined by Bonin, de Mier, and Noy. These are delta matroids whose feasible sets are in bijection with lattice paths which are symmetric along the main…

组合数学 · 数学 2023-11-28 Douglas M. Chen , Mario Sanchez , John Veliz , Zhiyan Ying

We prove that the Tutte polynomial of a coloopless paving matroid is convex along the portions of the line segments x+y=p lying in the positive quadrant. Every coloopless paving matroids is in the class of matroids which contain two…

组合数学 · 数学 2010-04-16 L. E. Chavez-Lomelí , C. Merino , S. D. Noble , M. Ramírez-Ibañez

We study rank-three matroids, known as point-line configurations, and their associated matroid varieties, defined as the Zariski closures of their realization spaces. Our focus is on determining finite generating sets of defining equations…

组合数学 · 数学 2025-06-10 Emiliano Liwski , Fatemeh Mohammadi , Lisa Vandebrouck

Every minor-closed class of matroids of bounded branch-width can be characterized by a list of excluded minors, but unlike graphs, this list may need to be infinite in general. However, for each fixed finite field $\mathbb F$, the list…

组合数学 · 数学 2025-08-15 Mamadou Mostapha Kanté , Eun Jung Kim , O-joung Kwon , Sang-il Oum

We study a class of polynomials that has all of its roots on the critical line and shares many properties with Ehrhart polynomials. Braun showed that the roots of Ehrhart polynomials are bounded quadratically and Higashitani provided…

组合数学 · 数学 2022-07-19 Max Kölbl

Given two finite matroids on the same ground set, a celebrated result of Edmonds says that the ground set can be partitioned into two disjoint subsets in a manner that there is a common independent set in both matroids whose intersection…

组合数学 · 数学 2025-01-27 Irfan Alam

There is a well-established dictionary between zonotopes, hyperplane arrangements, and their (oriented) matroids. Arguably one of the most famous examples is the class of graphical zonotopes, also called acyclotopes, which encode…

组合数学 · 数学 2024-09-24 Eleonore Bach , Matthias Beck , Sophie Rehberg