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Based on the notion of vectors and linear subspaces for a matroid, we develop a theory of flats and hyperplane arrangements for T-matroids, where T is a tract. This leads to several cryptomorphic descriptions of T-matroids: in terms of its…

Combinatorics · Mathematics 2026-03-11 Jannis Koulman , Oliver Lorscheid

We provide a short proof of a conic version of the colorful Carath\'eodory theorem for oriented matroids. Holmsen's extension of the colorful Carath\'eodory theorem to oriented matroids (Advances in Mathematics, 2016) already encompasses…

Combinatorics · Mathematics 2025-09-26 Minho Cho , Seunghun Lee , Frédéric Meunier

It is possible to write the indicator function of any matroid polytope as an integer combination of indicator functions of Schubert matroid polytopes. In this way, every matroid on $n$ elements of rank $r$ can be thought of as a lattice…

Combinatorics · Mathematics 2025-08-14 Luis Ferroni , Alex Fink

With every family of finitely many subsets of a finite-dimensional vector space over the Galois-field with two elements we associate a cyclic transversal polytope. It turns out that those polytopes generalize several well-known polytopes…

Combinatorics · Mathematics 2024-04-10 Jonas Frede , Volker Kaibel , Maximilian Merkert

We study transversality for Lipschitz-Fredholm maps in the context of bounded Fr\'{e}chet manifolds. We show that the set of all Lipschitz-Fredholm maps of a fixed index between Fr\'{e}chet spaces has the transverse stability property. We…

Differential Geometry · Mathematics 2016-04-01 Kaveh Eftekharinasab

An infinite matroid is graphic if all of its finite minors are graphic and the intersection of any circuit with any cocircuit is finite. We show that a matroid is graphic if and only if it can be represented by a graph-like topological…

Combinatorics · Mathematics 2013-09-17 Nathan Bowler , Johannes Carmesin , Robin Christian

In this series we introduce and investigate the concept of connectoids, which captures the connectivity structure of various discrete objects like undirected graphs, directed graphs, bidirected graphs, hypergraphs or finitary matroids. In…

Combinatorics · Mathematics 2025-06-17 Nathan Bowler , Florian Reich

In this paper we extend the theory of oriented matroids to Lagrangian orthogonal matroids and their representations, and give a completely natural transformation from a representation of a classical oriented matroid to a representation of…

Combinatorics · Mathematics 2007-05-23 Richard F. Booth

Given a homogeneous ideal $I$ in a polynomial ring over a field, one may record, for each degree $d$ and for each polynomial $f\in I_d$, the set of monomials in $f$ with nonzero coefficients. These data collectively form the tropicalization…

Algebraic Geometry · Mathematics 2021-03-01 Rob Silversmith

Several properties of the isotropic matroid of a looped simple graph are presented. Results include a characterization of the multimatroids that are associated with isotropic matroids and several ways in which the isotropic matroid of G…

Combinatorics · Mathematics 2016-10-20 Robert Brijder , Lorenzo Traldi

We introduce a sheaf-theoretic approach to tropical homology, especially for tropical homology with potentially non-compact supports. Our setup is suited to study the functorial properties of tropical homology, and we show that it behaves…

Algebraic Geometry · Mathematics 2019-06-24 Andreas Gross , Farbod Shokrieh

Let $k,d,\lambda\geqslant1$ be integers with $d\geqslant\lambda $. Let $m(k,d,\lambda)$ be the maximum positive integer $n$ such that every set of $n$ points (not necessarily in general position) in $\mathbb{R}^{d}$ has the property that…

We extend vector configurations to more general objects that have nicer combinatorial and topological properties, called weighted pseudosphere arrangements. These are defined as a weighted variant of arrangements of pseudospheres, as in the…

Metric Geometry · Mathematics 2019-06-11 Michael Gene Dobbins

We show how to equip the cone complexes of toroidal embeddings with additional structure that allows to define a balancing condition for weighted subcomplexes. We then proceed to develop the foundations of an intersection theory on cone…

Algebraic Geometry · Mathematics 2018-02-07 Andreas Gross

A well-known conjecture of Stanley is that the h-vector of a matroid is a pure O-sequence. There have been numerous papers with partial progress on this conjecture, but it is still wide open. In particular, for graphic matroids coming from…

Combinatorics · Mathematics 2021-09-06 Jacob David , Pierce Lai , SuHo Oh , Christopher Wu

To a vector configuration one can associate a polynomial ideal generated by powers of linear forms, known as a power ideal, which exhibits many combinatorial features of the matroid underlying the configuration. In this note we observe that…

Combinatorics · Mathematics 2018-05-21 Camilo Sarmiento

This paper compares skew-linear and multilinear matroid representations. These are matroids that are representable over division rings and (roughly speaking) invertible matrices, respectively. The main tool is the von Staudt construction,…

Combinatorics · Mathematics 2025-05-21 Lukas Kühne , Rudi Pendavingh , Geva Yashfe

Stanley has conjectured that the h-vector of a matroid complex is a pure O-sequence. We will prove this for cotransversal matroids by using generalized permutohedra. We construct a bijection between lattice points inside a r-dimensional…

Combinatorics · Mathematics 2012-10-04 SuHo Oh

A mixed graph is a graph with some directed edges and some undirected edges. We introduce the notion of mixed matroids as a generalization of mixed graphs. A mixed matroid can be viewed as an oriented matroid in which the signs over a fixed…

Combinatorics · Mathematics 2007-05-23 J. Orestes Cerdeira , Raul Cordovil

Coxeter matroids generalize matroids just as flag varieties of Lie groups generalize Grassmannians. Valuations of Coxeter matroids are functions that behave well with respect to subdivisions of a Coxeter matroid into smaller ones. We…

Combinatorics · Mathematics 2021-01-27 Christopher Eur , Mario Sanchez , Mariel Supina