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We introduce a dense counterpart of graph degeneracy, which extends the recently-proposed invariant symmetric difference. We say that a graph has sd-degeneracy (for symmetric-difference degeneracy) at most $d$ if it admits an elimination…

Data Structures and Algorithms · Computer Science 2024-05-16 Édouard Bonnet , Julien Duron , John Sylvester , Viktor Zamaraev

We construct classes of graphs that are variants of the so-called layered wheel. One of their key properties is that while the treewidth is bounded by a function of the clique number, the construction can be adjusted to make the dependance…

Combinatorics · Mathematics 2025-11-04 Maria Chudnovsky , Nicolas Trotignon

A variety of powerful extremal results have been shown for the chromatic number of triangle-free graphs. Three noteworthy bounds are in terms of the number of vertices, edges, and maximum degree given by Poljak \& Tuza (1994), and…

Combinatorics · Mathematics 2023-10-13 David G. Harris

We introduce the {\it endomorphism distinguishing number} $D_e(G)$ of a graph $G$ as the least cardinal $d$ such that $G$ has a vertex coloring with $d$ colors that is only preserved by the trivial endomorphism. This generalizes the notion…

Combinatorics · Mathematics 2013-11-28 Wilfried Imrich , Rafał Kalinowski , Florian Lehner , Monika Pilśniak

This paper deals with the maximum value of the difference between the determining number and the metric dimension of a graph as a function of its order. Our technique requires to use locating-dominating sets, and perform an independent…

Combinatorics · Mathematics 2014-01-16 Delia Garijo , Antonio González , Alberto Márquez

The numbers game is a one-player game played on a finite simple graph with certain "amplitudes" assigned to its edges and with an initial assignment of real numbers to its nodes. The moves of the game successively transform the numbers at…

Combinatorics · Mathematics 2008-10-31 Robert G. Donnelly

The junction-tree representation provides an attractive structural property for organizing a decomposable graph. In this study, we present two novel stochastic algorithms, which we call the junction-tree expander and junction-tree collapser…

Statistics Theory · Mathematics 2021-02-16 Jimmy Olsson , Tetyana Pavlenko , Felix L. Rios

We prove a lower bound on the number of spanning two-forests in a graph, in terms of the number of vertices, edges, and spanning trees. This implies an upper bound on the average cut size of a random two-forest. The main tool is an identity…

Combinatorics · Mathematics 2023-08-09 Harry Richman , Farbod Shokrieh , Chenxi Wu

In this paper we compare the brushing number of a graph with the zero-forcing number of its line graph. We prove that the zero-forcing number of the line graph is an upper bound for the brushing number by constructing a brush configuration…

Combinatorics · Mathematics 2020-08-25 Aras Erzurumluoglu , David Pike , Karen Meagher

A contraction sequence of a graph consists of iteratively merging two of its vertices until only one vertex remains. The recently introduced twin-width graph invariant is based on contraction sequences. More precisely, if one puts red edges…

Data Structures and Algorithms · Computer Science 2022-06-02 Édouard Bonnet , Eun Jung Kim , Amadeus Reinald , Stéphan Thomassé

Given a linear ordering of the vertices of a graph, the cutwidth of a vertex $v$ with respect to this ordering is the number of edges from any vertex before $v$ (including $v$) to any vertex after $v$ in this ordering. The cutwidth of an…

Optimization and Control · Mathematics 2024-12-05 Elisabeth Gaar , Diane Puges , Angelika Wiegele

This survey on graphs of large girth consists of two parts. The first deals with some aspects of algebraic and extremal graph theory loosely related to the Moore bound. Our point of departure for the second, Ramsey theoretic, part are some…

Combinatorics · Mathematics 2024-03-21 Christian Reiher

We determine the sharp threshold for the containment of all $n$-vertex trees of bounded degree in random geometric graphs with $n$ vertices. This provides a geometric counterpart of Montgomery's threshold result for binomial random graphs,…

Combinatorics · Mathematics 2025-05-23 Michael Anastos , Sahar Diskin , Dawid Ignasiak , Lyuben Lichev , Yetong Sha

We introduce the price of symmetrisation, a concept that aims to compare fundamental differences (gap and quotient) between values of a given graph invariant for digraphs and the values of the same invariant of the symmetric versions of…

Discrete Mathematics · Computer Science 2013-10-11 Absil Romain , Hadrien Mélot

This paper addresses the behavior of the Lov\'asz number for dense random circulant graphs. The Lov\'asz number is a well-known semidefinite programming upper bound on the independence number. Circulant graphs, an example of a Cayley graph,…

We present a constraint model for the problem of producing a tree decomposition of a graph. The inputs to the model are a simple graph G, the number of nodes in the desired tree decomposition and the maximum cardinality of each node in that…

Discrete Mathematics · Computer Science 2019-08-08 Benjamin Bumpus , Patrick Prosser , James Trimble

For every connected graph $G$ and surface $S$, we consider the well-known string of inequalities $\delta_S(G) \leq \mu_S(G) \leq \nu_S(G)$, where $\mu$ and $\nu$ denote skewness and crossing number and $\delta$ is the Euler-formula lower…

Combinatorics · Mathematics 2025-01-07 Paul C. Kainen

We study the interplay between chip-firing games and potential theory on graphs, characterizing reduced divisors ($G$-parking functions) on graphs as the solution to an energy (or potential) minimization problem and providing an algorithm…

Combinatorics · Mathematics 2012-07-31 Matthew Baker , Farbod Shokrieh

We here investigate on the complexity of computing the \emph{tree-length} and the \emph{tree-breadth} of any graph $G$, that are respectively the best possible upper-bounds on the diameter and the radius of the bags in a tree decomposition…

Computational Complexity · Computer Science 2016-01-11 Guillaume Ducoffe , Sylvain Legay , Nicolas Nisse

This paper studies the structure of graphs with given tree-width and excluding a fixed complete bipartite subgraph, which generalises the bounded degree setting. We give a new structural description of such graphs in terms of so-called…

Combinatorics · Mathematics 2025-12-15 Chun-Hung Liu , David R. Wood