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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

An $(n, k_1, \dots, k_t)$-cross intersecting system is a set of non-empty pairwise cross-intersecting families $\mathcal{F}_1\subset{[n]\choose k_1}, \mathcal{F}_2\subset{[n]\choose k_2}, \dots, \mathcal{F}_t\subset{[n]\choose k_t}$ with…

Combinatorics · Mathematics 2023-10-30 Yang Huang , Yuejian Peng

In this article we give explicit descriptions of the multiplicities of some classes of monomial ideals. For instance, we give a formula for the multiplicities of all codimension 1 monomial ideals, and another formula for the multiplicities…

Commutative Algebra · Mathematics 2019-01-29 Guillermo Alesandroni

The problem of bounding the size of a set system under various intersection restrictions has a central place in extremal combinatorics. We investigate the maximum number of disjoint pairs a set system can have in this setting. In…

Combinatorics · Mathematics 2019-08-13 António Girão , Richard Snyder

We investigate gcd-monoids, which are cancellative monoids in which any two elements admit a left and a right gcd, and the associated reduction of multifractions (arXiv:1606.08991 and 1606.08995), a general approach to the word problem for…

Group Theory · Mathematics 2017-01-31 Patrick Dehornoy , Friedrich Wehrung

Motivated by the study of word problems of monoids, we explore two ways of viewing binary relations on $A^*$ as languages. We exhibit a hierarchy of classes of binary relations on $A^*$, according to the class of languages the relation…

Formal Languages and Automata Theory · Computer Science 2018-12-06 Tara Brough , Alan J. Cain

Let $ k, m, n $ be positive integers with $ k \geq 2 $. A $ k $-multiset of $ [n]_m $ is a collection of $ k $ integers from the set $ \{1, 2, \ldots, n\} $ in which the integers can appear more than once but at most $ m $ times. A family…

Combinatorics · Mathematics 2023-03-14 Jiaqi Liao , Zequn Lv , Mengyu Cao , Mei Lu

A generalization of pairwise intersecting Minkowski arrangement of centrally symmetric convex bodies is the pairwise intersecting Minkowski arrangement of order $\mu$. Here, the homothetic copies of a centrally symmetric convex body are so…

Metric Geometry · Mathematics 2020-02-20 Viktória Földvári

Despite a surge of interest in submodular maximization in the data stream model, there remain significant gaps in our knowledge about what can be achieved in this setting, especially when dealing with multiple constraints. In this work, we…

Data Structures and Algorithms · Computer Science 2022-04-12 Moran Feldman , Ashkan Norouzi-Fard , Ola Svensson , Rico Zenklusen

We address a specific case of the matroid intersection problem: given a set of graphs sharing the same set of vertices, select a minimum cycle basis for each graph to maximize the size of their intersection. We provide a comprehensive…

Computational Complexity · Computer Science 2024-04-29 Dimitri Watel , Marc-Antoine Weisser , Dominique Barth , Ylène Aboulfath , Thierry Mautor

Consider a family of sets and a single set, called the query set. How can one quickly find a member of the family which has a maximal intersection with the query set? Time constraints on the query and on a possible preprocessing of the set…

Information Retrieval · Computer Science 2010-04-02 Benjamin Hoffmann , Mikhail Lifshits , Yury Lifshits , Dirk Nowotka

Let $ k, n \in \mathbb{N}^+ $ and $ m \in \mathbb{N}^+ \cup \{\infty \} $. A $ k $-multiset in $ [n]_m $ is a $ k $-set whose elements are integers from $ \{1, 2, \ldots, n\} $, and each element is allowed to have at most $ m $ repetitions.…

Combinatorics · Mathematics 2024-07-09 Jiaqi Liao , Zequn Lv , Mengyu Cao , Mei Lu

For $n > 2k \geq 4$ we consider intersecting families $\mathcal F$ consisting of $k$-subsets of $\{1, 2, \ldots, n\}$. Let $\mathcal I(\mathcal F)$ denote the family of all distinct intersections $F \cap F'$, $F \neq F'$ and $F, F'\in…

Combinatorics · Mathematics 2021-08-03 Peter Frankl , Sergei Kiselev , Andrey Kupavskii

Two families of sets \(\mathcal{A}\) and \(\mathcal{B}\) are called \emph{cross-\(t\)-intersecting} if \(|A \cap B| \geq t\) for all \(A \in \mathcal{A}\) and \(B \in \mathcal{B}\). Determining the maximum product of sizes for such…

Combinatorics · Mathematics 2025-10-15 Jingjun Bao , Lijun Ji

In this note, we first bound the intersection number of the regular simplicial partitions.

Metric Geometry · Mathematics 2022-11-09 Zhiheng Zhang

We study the maximum multiplicity $\mathcal{M}(k,n)$ of a simple transposition $s_k=(k \: k+1)$ in a reduced word for the longest permutation $w_0=n \: n-1 \: \cdots \: 2 \: 1$, a problem closely related to much previous work on sorting…

Combinatorics · Mathematics 2024-10-04 Christian Gaetz , Yibo Gao , Pakawut Jiradilok , Gleb Nenashev , Alexander Postnikov

This is the first part of a series of three strongly related papers in which three equivalent structures are studied: - internal categories in categories of monoids; defined in terms of pullbacks relative to a chosen class of spans -…

Category Theory · Mathematics 2018-03-12 Gabriella Böhm

In this paper, we address several intersection problems for $r$-cross $t$-intersecting families of partitions. A $k$-partition of an $n$-set $X$ is a set of $k$ pairwise disjoint non-empty subsets whose union is $X$. For $1\leq i\leq r$,…

Combinatorics · Mathematics 2026-02-24 Jie Wen , Benjian Lv

We make some progress on a question of Babai from the 1970s, namely: for $n, k \in \mathbb{N}$ with $k \le n/2$, what is the largest possible cardinality $s(n,k)$ of an intersecting family of $k$-element subsets of $\{1,2,\ldots,n\}$…

Combinatorics · Mathematics 2022-06-10 David Ellis , Gil Kalai , Bhargav Narayanan

Maximal $(k+1)$-crossing-free graphs on a planar point set in convex position, that is, $k$-triangulations, have received attention in recent literature, with motivation coming from several interpretations of them. We introduce a new way of…

Combinatorics · Mathematics 2012-06-14 Vincent Pilaud , Francisco Santos