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Cross-ratio degrees count configurations of points $z_1,\ldots, z_n \in \mathbb{P}^1$ satisfying $n - 3$ cross-ratio constraints, up to isomorphism. These numbers arise in multiple contexts in algebraic and tropical geometry, and may be…

Algebraic Geometry · Mathematics 2021-08-10 Rob Silversmith

We introduce and study randomized sequential importance sampling algorithms for estimating the number of perfect matchings in bipartite graphs. In analyzing their performance, we establish various non-standard central limit theorems. We…

Probability · Mathematics 2025-11-18 Persi Diaconis , Brett Kolesnik

In this paper, we consider the problems of enumerating minimal vertex covers and minimal dominating sets with capacity and/or connectivity constraints. We develop polynomial-delay enumeration algorithms for these problems on bounded-degree…

Data Structures and Algorithms · Computer Science 2024-11-15 Yasuaki Kobayashi , Kazuhiro Kurita , Kevin Mann , Yasuko Matsui , Hirotaka Ono

A locally-optimal structure is a combinatorial structure such as a maximal independent set that cannot be improved by certain (greedy) local moves, even though it may not be globally optimal. It is trivial to construct an independent set in…

Computational Complexity · Computer Science 2016-04-20 Leslie Ann Goldberg , Rob Gysel , John Lapinskas

In 2019, P. Higgins formulated [1] a question about bipartite graphs (see Conjecture 1 below); this question arises in the study of regular finite semigroups. F. V. Petrov formulated [2] another combinatorial conjecture (Conjecture 3);…

Combinatorics · Mathematics 2026-03-20 Ilya I. Bogdanov , Fedor Petrov , Anton Sadovnichiy , Fedor Ushakov

Finding dense bipartite subgraphs and detecting the relations among them is an important problem for affiliation networks that arise in a range of domains, such as social network analysis, word-document clustering, the science of science,…

Social and Information Networks · Computer Science 2017-11-29 A. Erdem Sariyuce , Ali Pinar

This paper explores combinatorial optimization for problems of max-weight graph matching on multi-partite graphs, which arise in integrating multiple data sources. Entity resolution-the data integration problem of performing noisy joins on…

Databases · Computer Science 2014-02-04 Duo Zhang , Benjamin I. P. Rubinstein , Jim Gemmell

We consider the number of independent sets in hypergraphs, which allows us to define the independence density of countable hypergraphs. Hypergraph independence densities include a broad family of densities over graphs and relational…

Combinatorics · Mathematics 2013-08-14 Anthony Bonato , Jason Brown , Dieter Mitsche , Pawel Pralat

A maximal independent set in a graph $G$ is an independent set that cannot be extended to a larger independent set by adding any vertex from $G$. This paper investigates the problem of determining the maximum number of maximal independent…

Combinatorics · Mathematics 2025-06-02 Yongtang Shi , Jianhua Tu , Ziyuan Wang

Let $\mathrm{pm}(G)$ denote the number of perfect matchings of a graph $G$, and let $K_{r\times 2n/r}$ denote the complete $r$-partite graph where each part has size $2n/r$. Johnson, Kayll, and Palmer conjectured that for any perfect…

Combinatorics · Mathematics 2022-11-04 Sam Spiro , Erlang Surya

We define a perfect coloring of a graph $G$ as a proper coloring of $G$ such that every connected induced subgraph $H$ of $G$ uses exactly $\omega(H)$ many colors where $\omega(H)$ is the clique number of $H$. A graph is perfectly colorable…

Combinatorics · Mathematics 2011-08-15 R B Sandeep

In the area of beyond-planar graphs, i.e. graphs that can be drawn with some local restrictions on the edge crossings, the recognition problem is prominent next to the density question for the different graph classes. For 1-planar graphs,…

Data Structures and Algorithms · Computer Science 2021-08-04 Henry Förster , Michael Kaufmann , Chrysanthi N. Raftopoulou

The strong geodetic problem is to find the smallest number of vertices such that by fixing one shortest path between each pair, all vertices of the graph are covered. In this paper we study the strong geodetic problem on complete bipartite…

Combinatorics · Mathematics 2018-06-04 Vesna Iršič , Matjaž Konvalinka

We analyze the computational complexity of the following computational problems called Bounded-Density Edge Deletion and Bounded-Density Vertex Deletion: Given a graph $G$, a budget $k$ and a target density $\tau_\rho$, are there $k$ edges…

Data Structures and Algorithms · Computer Science 2024-04-15 Cristina Bazgan , André Nichterlein , Sofia Vazquez Alferez

Exact pattern matching in labeled graphs is the problem of searching paths of a graph $G=(V,E)$ that spell the same string as the given pattern $P[1..m]$. This basic problem can be found at the heart of more complex operations on variation…

Computational Complexity · Computer Science 2019-02-12 Massimo Equi , Roberto Grossi , Alexandru I. Tomescu , Veli Mäkinen

An {\em antimagic labeling} of a graph with $m$ edges and $n$ vertices is a bijection from the set of edges to the integers $1,...,m$ such that all $n$ vertex sums are pairwise distinct, where a vertex sum is the sum of labels of all edges…

Combinatorics · Mathematics 2007-05-23 N. Alon , G. Kaplan , A. Lev , Y. Roditty , R. Yuster

For c in [0,1] let P_n(c) denote the set of n-vertex perfect graphs with density c and C_n(c) the set of n-vertex graphs without induced C_5 and with density c. We show that log|P_n(c)|/binom{n}{2}=log|C_n(c)|/binom{n}{2}=h(c)+o(1) with…

Combinatorics · Mathematics 2011-02-28 Julia Böttcher , Anusch Taraz , Andreas Würfl

A graph G is well-covered if all its maximal independent sets are of the same cardinality. Assume that a weight function w is defined on its vertices. Then G is w-well-covered if all maximal independent sets are of the same weight. For…

Discrete Mathematics · Computer Science 2016-11-22 Vadim E. Levit , David Tankus

We study the perfect matching reconfiguration problem: Given two perfect matchings of a graph, is there a sequence of flip operations that transforms one into the other? Here, a flip operation exchanges the edges in an alternating cycle of…

Data Structures and Algorithms · Computer Science 2019-04-15 Marthe Bonamy , Nicolas Bousquet , Marc Heinrich , Takehiro Ito , Yusuke Kobayashi , Arnaud Mary , Moritz Mühlenthaler , Kunihiro Wasa

We examine the problem of exactly or approximately counting all perfect matchings in hereditary classes of nonbipartite graphs. In particular, we consider the switch Markov chain of Diaconis, Graham and Holmes. We determine the largest…

Discrete Mathematics · Computer Science 2018-02-27 Martin Dyer , Haiko Müller