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We prove that if $ M $ and $ N $ are finitary matroids on a common countable edge set $ E $ then they admit a common independent set $I $ such that there is a bipartition $ E=E_{M}\cup E_{N} $ for which $ I\cap E_M $ spans $ E_M $ in $ M $…

Combinatorics · Mathematics 2021-04-06 Attila Joó

We show that the infinite matroid intersection conjecture of Nash-Williams implies the infinite Menger theorem proved recently by Aharoni and Berger. We prove that this conjecture is true whenever one matroid is nearly finitary and the…

Combinatorics · Mathematics 2012-07-10 Elad Aigner-Horev , Johannes Carmesin , Jan-Oliver Fröhlich

Using a new technique, we prove a rich family of special cases of the matroid intersection conjecture. Roughly, we prove the conjecture for pairs of tame matroids which have a common decomposition by 2-separations into finite parts.

Combinatorics · Mathematics 2014-04-25 Nathan Bowler , Johannes Carmesin

Matroid is a generalization of many fundamental objects in combinatorial mathematics , and matroid intersection problem is a classical subject in combinatorial optimization . However , only the intersection of two matroids are well…

Combinatorics · Mathematics 2023-01-10 Tianyu Liu

For (potentially infinite) matroids $ M $ and $ N $, an $ (M,N) $-hindrance is a set $ H$ that is independent but not spanning in $ N.\mathsf{span}_M(H) $. This concept was introduced by Aharoni and Ziv in the very first paper investigating…

Combinatorics · Mathematics 2025-02-27 Attila Joó

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…

Combinatorics · Mathematics 2025-01-27 Irfan Alam

As part of the recent developments in infinite matroid theory, there have been a number of conjectures about how standard theorems of finite matroid theory might extend to the infinite setting. These include base packing, base covering, and…

Combinatorics · Mathematics 2012-03-06 Nathan Bowler , Johannes Carmesin

We construct some matroids that have a circuit and a cocircuit with infinite intersection. This answers a question of Bruhn, Diestel, Kriesell, Pendavingh and Wollan. It further shows that the axiom system for matroids proposed by Dress…

Combinatorics · Mathematics 2012-02-29 Johannes Carmesin , Nathan Bowler

The Packing/Covering Conjecture was introduced by Bowler and Carmesin motivated by the Matroid Partition Theorem by Edmonds and Fulkerson. A packing for a family $ (M_i: i\in\Theta) $ of matroids on the common edge set $ E $ is a system $…

Combinatorics · Mathematics 2021-03-30 Attila Joó

A famous theorem of Galvin states that the list chromatic number of the intersection of two partition matroids equals its chromatic number. Kiraly and Berczi et. al. conjectured that this equality holds for any two matroids. We prove this…

Combinatorics · Mathematics 2024-07-15 He Guo

In this paper, we investigate the classes of matroid intersection admitting a solution for the problem of partitioning the ground set $E$ into $k$ common independent sets, where $E$ can be partitioned into $k$ independent sets in each of…

Combinatorics · Mathematics 2019-01-29 Kenjiro Takazawa , Yu Yokoi

This paper shows a polynomial-time algorithm, that given a general matroid $M_1 = (X, \mathcal{I}_1)$ and $k-1$ partition matroids $ M_2, \ldots, M_k$, produces a coloring of the intersection $M = \cap_{i=1}^k M_i$ using at most…

Data Structures and Algorithms · Computer Science 2025-08-28 Stephen Arndt , Benjamin Moseley , Kirk Pruhs , Michael Zlatin

A subset $S$ of $\mathbb R^d$ has the Borsuk property if it can be decomposed into at most $d+1$ parts of diameter smaller than $S$. This is an important geometric property, inspired by a conjecture of Borsuk from the 1930s, which has…

Combinatorics · Mathematics 2025-06-23 Gyivan López-Campos , Frédéric Meunier , Jorge L. Ramírez Alfonsín

In this paper, we investigate three problems concerning the toric ideal associated to a matroid. Firstly, we list all matroids $\mathcal M$ such that its corresponding toric ideal $I_{\mathcal M}$ is a complete intersection. Secondly, we…

Commutative Algebra · Mathematics 2017-01-17 Ignacio García-Marco , Jorge Luis Ramírez Alfonsín

Matroid intersection is one of the most powerful frameworks of matroid theory that generalizes various problems in combinatorial optimization. Edmonds' fundamental theorem provides a min-max characterization for the unweighted setting,…

Data Structures and Algorithms · Computer Science 2023-02-07 Kristóf Bérczi , Tamás Király , Yutaro Yamaguchi , Yu Yokoi

Given two matroids $\mathcal{M}_1$ and $\mathcal{M}_2$ over the same $n$-element ground set, the matroid intersection problem is to find a largest common independent set, whose size we denote by $r$. We present a simple and generic auction…

Data Structures and Algorithms · Computer Science 2024-10-22 Joakim Blikstad , Ta-Wei Tu

Let $A$ be a graded complete intersection over a field and $B$ the monomial complete intersection with the generators of the same degrees as $A$. The EGH conjecture says that if $I$ is a graded ideal in $A$, then there should be an ideal…

Commutative Algebra · Mathematics 2016-01-27 Tadahito Harima , Akihito Wachi , Junzo Watanabe

Let $\mathcal{M}$ and $\mathcal{N}$ be two matroids on the same ground set $V$. Let $A_1,\dots,A_{2n-1}$ be sets which are independent in both $\mathcal{M}$ and $\mathcal{N}$, satisfying $|A_i|\geq \textrm{min}(i,n)$ for all $i$. We show…

Combinatorics · Mathematics 2025-11-06 Eli Berger , Daniel McGinnis

This work investigates the intersection property of conditional independence. It states that for random variables $A,B,C$ and $X$ we have that $X$ independent of $A$ given $B,C$ and $X$ independent of $B$ given $A,C$ implies $X$ independent…

Probability · Mathematics 2016-08-18 Jonas Peters

Two families $\mathcal{A}$ and $\mathcal{B}$ of sets are said to be cross-intersecting if each member of $\mathcal{A}$ intersects each member of $\mathcal{B}$. For any two integers $n$ and $k$ with $0 \leq k \leq n$, let ${[n] \choose \leq…

Combinatorics · Mathematics 2015-06-12 Peter Borg
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