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Consider a drawing of a graph $G$ in the plane such that crossing edges are coloured differently. The minimum number of colours, taken over all drawings of $G$, is the classical graph parameter "thickness". By restricting the edges to be…

Combinatorics · Mathematics 2015-06-17 Vida Dujmović , David R. Wood

Let $H$ and $G$ be two finite graphs. Define $h_H(G)$ to be the number of homomorphisms from $H$ to $G$. The function $h_H(\cdot)$ extends in a natural way to a function from the set of symmetric matrices to $\mathbb{R}$ such that for…

Functional Analysis · Mathematics 2008-06-03 Hamed Hatami

Let $G$ be a finite, connected metric graph and let $X\subseteq G$ be a subset. If $X$ is sufficiently dense in $G$, we show that the Gromov--Hausdorff distance matches the Hausdorff distance, namely $d_\gh(G,X)=d_\h(G,X)$. When the metric…

Metric Geometry · Mathematics 2025-12-24 Henry Adams , Sushovan Majhi , Fedor Manin , Žiga Virk , Nicolò Zava

Given a graph $G$ and a target graph $H$, an $H$-coloring of $G$ is an adjacency-preserving vertex map from $G$ to $H$. The number of $H$-colorings of $G$, $\hom(G,H)$, has been studied for many classes of $G$ and $H$. In particular,…

Combinatorics · Mathematics 2026-01-01 David Galvin , Phillip Marmorino , Emily McMillon , JD Nir , Amanda Redlich

This paper presents a spectral framework for quantifying the differentiation between graph data samples by introducing a novel metric named Graph Geodesic Distance (GGD). For two different graphs with the same number of nodes, our framework…

Machine Learning · Computer Science 2025-08-18 Soumen Sikder Shuvo , Ali Aghdaei , Zhuo Feng

The goal of this work is to give precise bounds on the counting complexity of a family of generalized coloring problems (list homomorphisms) on bounded-treewidth graphs. Given graphs $G$, $H$, and lists $L(v)\subseteq V(H)$ for every $v\in…

Computational Complexity · Computer Science 2021-11-01 Jacob Focke , Dániel Marx , Paweł Rzążewski

Treedepth, a more restrictive graph width parameter than treewidth and pathwidth, plays a major role in the theory of sparse graph classes. We show that there exists a constant $C$ such that for every positive integers $a,b$ and a graph…

Discrete Mathematics · Computer Science 2019-09-19 Wojciech Czerwiński , Wojciech Nadara , Marcin Pilipczuk

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

We show that every connected graph $G$ has a tree decomposition indexed by a tree $T$ such that $T$ is a subgraph of $G$ and the width of the tree decomposition is bounded from above by a function of the pathwidth of $G$. This answers a…

Combinatorics · Mathematics 2026-03-02 Romain Bourneuf , Gwenaël Joret , Piotr Micek , Martin Milanič , Michał Pilipczuk

For any fixed graph $G$, the subgraph isomorphism problem asks whether an $n$-vertex input graph has a subgraph isomorphic to $G$. A well-known algorithm of Alon, Yuster and Zwick (1995) efficiently reduces this to the "colored" version of…

Computational Complexity · Computer Science 2020-11-04 Gregory Rosenthal

The graph similarity problem, also known as approximate graph isomorphism or graph matching problem, has been extensively studied in the machine learning community, but has not received much attention in the algorithms community: Given two…

Data Structures and Algorithms · Computer Science 2018-02-26 Martin Grohe , Gaurav Rattan , Gerhard J. Woeginger

The study of the topological structure of complex networks has fascinated researchers for several decades, and today we have a fairly good understanding of the types and reoccurring characteristics of many different complex networks.…

Social and Information Networks · Computer Science 2014-06-23 Matthieu Roy , Stefan Schmid , Gilles Trédan

Given two non-empty graphs $H$ and $T$, write $H\succcurlyeq T$ to mean that $t(H,G)^{|E(T)|}\geq t(T,G)^{|E(H)|}$ for every graph $G$, where $t(\cdot,\cdot)$ is the homomorphism density function. We obtain various necessary and sufficient…

Combinatorics · Mathematics 2025-01-08 Natalie Behague , Gabriel Crudele , Jonathan A. Noel , Lina M. Simbaqueba

Graph alignment - identifying node correspondences between two graphs - is a fundamental problem with applications in network analysis, biology, and privacy research. While substantial progress has been made in aligning correlated…

Information Theory · Computer Science 2026-03-16 Jakob Maier , Laurent Massoulié

We prove that the (divisorial) gonality of a finite connected graph is lower bounded by its treewidth. We show that equality holds for grid graphs and complete multipartite graphs. We prove that the treewidth lower bound also holds for…

Combinatorics · Mathematics 2022-01-04 Josse van Dobben de Bruyn , Dion Gijswijt

A connected subgraph of a graph is isometric if it preserves distances. In this short note, we provide counterexamples to several variants of the following general question: When a graph $G$ is edge covered by connected isometric subgraphs…

Combinatorics · Mathematics 2025-11-06 Paul Bastide , Julien Duron , Jędrzej Hodor , Weichan Liu , Xiangxiang Nie

We construct a pair of non-isomorphic, bipartite graphs which are not distinguished by counting the number of homomorphisms to any tree. This answers a question motivated by Atserias et al. (LICS 2021). In order to establish the…

Discrete Mathematics · Computer Science 2025-11-19 Anuj Dawar

For a fixed "pattern" graph $G$, the $\textit{colored $G$-subgraph isomorphism problem}$ (denoted $\mathrm{SUB}(G)$) asks, given an $n$-vertex graph $H$ and a coloring $V(H) \to V(G)$, whether $H$ contains a properly colored copy of $G$.…

Computational Complexity · Computer Science 2020-04-29 Deepanshu Kush , Benjamin Rossman

Two graph parameters are said to be coarsely equivalent if they are within constant factors from each other for every graph $G$. Recently, several graph parameters were shown to be coarsely equivalent to tree-length. Recall that the length…

Combinatorics · Mathematics 2025-04-02 Feodor F. Dragan , Ekkehard Köhler

We consider sequences of graphs and define various notions of convergence related to these sequences: ``left convergence'' defined in terms of the densities of homomorphisms from small graphs into the graphs of the sequence, and ``right…

Combinatorics · Mathematics 2007-05-23 C. Borgs , J. T. Chayes , L. Lovasz , V. T. Sos , K. Vesztergombi