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Let $a$ and $b$ be two positive integers with $a\leq b$, and let $G$ be a graph with vertex set $V(G)$ and edge set $E(G)$. Let $h:E(G)\rightarrow[0,1]$ be a function. If $a\leq\sum\limits_{e\in E_G(v)}{h(e)}\leq b$ holds for every $v\in…

Combinatorics · Mathematics 2023-09-19 Sizhong Zhou , Yuli Zhang

We consider three notions of connectivity and their interactions in partially ordered sets coming from reduced factorizations of an element in a generated group. While one form of connectivity essentially reflects the connectivity of the…

Combinatorics · Mathematics 2023-02-07 Henri Mühle , Vivien Ripoll

Let $k$, $m$ and $r$ be three integers such that $2\leq k\leq m\leq r$. Let $G$ be a $2r$-regular, $2m$-edge-connected graph of odd order. We obtain some sufficient conditions, which guarantee $G-v$ contains a $k$-factor for all $v\in…

Combinatorics · Mathematics 2010-07-27 Hongliang Lu , Bing Bai , Wei Wang

After seeing how questions on the finer distribution of prime factorization -- considered inaccessible until recently -- reduce to bounding the norm of an operator defined on a graph describing factorization, we will show how to bound that…

Number Theory · Mathematics 2022-01-04 Harald Andrés Helfgott

A path in an edge-colored graph is called a proper path if no two adjacent edges of the path receive the same color. For a connected graph $G$, the proper connection number $pc(G)$ of $G$ is defined as the minimum number of colors needed to…

Combinatorics · Mathematics 2016-02-25 Fei Huang , Xueliang Li , Zhongmei Qin , Colton Magnant

We establish a threshold for the connectivity of certain random graphs whose (dependent) edges are determined by the uniform distributions on generalized Orlicz balls, crucially using their negative correlation properties. We also show the…

Combinatorics · Mathematics 2020-12-03 Alan Frieze , Tomasz Tkocz

An identifying code is a subset of vertices of a graph such that each vertex is uniquely determined by its neighbourhood within the identifying code. If $\M(G)$ denotes the minimum size of an identifying code of a graph $G$, it was…

Discrete Mathematics · Computer Science 2012-09-24 Florent Foucaud , Guillem Perarnau

Let G be a connected graph. The toughness of G is defined as t(G)=min{\frac{|S|}{c(G-S)}}, in which the minimum is taken over all proper subsets S\subset V(G) such that c(G-S)\geq 2 where c(G-S) denotes the number of components of G-S.…

Combinatorics · Mathematics 2023-09-12 Dandan Fan , Xiaofeng Gu , Huiqiu Lin

The \emph{$k$-restricted edge-connectivity} of a graph $G$, denoted by $\lambda_k(G)$, is defined as the minimum size of an edge set whose removal leaves exactly two connected components each containing at least $k$ vertices. This graph…

Data Structures and Algorithms · Computer Science 2016-09-20 Luis Pedro Montejano , Ignasi Sau

Bipartite graph tiling was studied by Zhao who gave the best possible minimum degree conditions for a balanced bipartite graph on 2ms vertices to contain m vertex disjoint copies of K_{s,s}. Let s<t be fixed positive integers. Hladk\'y and…

Combinatorics · Mathematics 2015-03-19 Andrzej Czygrinow , Louis DeBiasio

For many types of graphs, criteria have been discovered that give necessary and sufficient conditions for an integer sequence to be the degree sequence of such a graph. These criteria tend to take the form of a set of inequalities, and in…

Combinatorics · Mathematics 2013-01-15 Jeffrey W. Miller

We characterise the form of all simple, finite graphs for which the girth of the graph is equal to the circumference of the graph. We apply this to prove a bound on the number of edges in such a graph.

Combinatorics · Mathematics 2022-10-11 Lewis Stanton , Jeffrey Thompson

It is a famous result of Lovasz and Yemini (1982) that 6-connected graphs are rigid in the plane. This was recently improved by Jackson and Jordan (2009) who showed that 6-mixed connectivity is also sufficient for rigidity. Here we give…

Combinatorics · Mathematics 2018-04-30 Viktoria E. Kaszanitzky , Bernd Schulze

A good edge-labelling of a simple graph is a labelling of its edges with real numbers such that, for any ordered pair of vertices (u,v), there is at most one nondecreasing path from u to v. Say a graph is good if it admits a good…

Combinatorics · Mathematics 2012-11-13 Abbas Mehrabian

A class of graphs is bridge-addable if given a graph $G$ in the class, any graph obtained by adding an edge between two connected components of $G$ is also in the class. We prove a conjecture of McDiarmid, Steger, and Welsh, that says that…

Combinatorics · Mathematics 2023-06-23 Guillaume Chapuy , Guillem Perarnau

An ordering of the vertices of a graph is \emph{connected} if every vertex (but the first) has a neighbor among its predecessors. The greedy colouring algorithm of a graph with a connected order consists in taking the vertices in order, and…

Discrete Mathematics · Computer Science 2018-06-08 Ngoc Khang Le , Nicolas Trotignon

Addressing a question posed by Chen and Ma from an asymptotic point of view, we present a short proof for the edge density needed to guarantee that two vertices of the same degree are connected by a path of a fixed length. In particular, we…

Combinatorics · Mathematics 2026-05-12 Yamaan Attwa , Matías Azócar Carvajal , Simona Boyadzhiyska , Théo Pierron , Anusch Taraz

We show that we can assume graphs that do not have the edge-Erd\H{o}s-P\'{o}sa property to be connected. Then we strengthen this result to $2$-connectivity under the additional assumptions of a minor-closed property and a generic…

Combinatorics · Mathematics 2023-07-24 Raphael Steck

A graph G is equimatchable if every maximal matching of G has the same cardinality. In this paper, we investigate equimatchable graphs such that the removal of any edge harms the equimatchability, called edge-critical equimatchable graphs…

Combinatorics · Mathematics 2022-02-17 Zakir Deniz , Tınaz Ekim

Let $H: V(G) \rightarrow 2^{\mathbb{N}}$ be a set mapping for a graph $G$. Given a spanning subgraph $F$ of $G$, $F$ is called a {\it general factor} or an $H$-{\it factor} of $G$ if $d_{F}(x)\in H(x)$ for every vertex $x\in V(G)$.…

Combinatorics · Mathematics 2011-04-28 Hongliang Lu , Qinglin Yu