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We introduce the concept of a class of graphs, or more generally, relational structures, being locally tree-decomposable. There are numerous examples of locally tree-decomposable classes, among them the class of planar graphs and all…

Data Structures and Algorithms · Computer Science 2007-05-23 Markus Frick , Martin Grohe

The two-player, complete information game of Cops and Robber is played on undirected finite graphs. A number of cops and one robber are positioned on vertices and take turns in sliding along edges. The cops win if, after a move, a cop and…

Combinatorics · Mathematics 2021-12-23 Gwenaël Joret , Marcin Kamiński , Dirk Oliver Theis

We consider a game in which a cop searches for a moving robber on a connected graph using distance probes, which is a slight variation on one introduced by Seager. Carragher, Choi, Delcourt, Erickson and West showed that for any $n$-vertex…

Combinatorics · Mathematics 2017-11-23 John Haslegrave , Richard A. B. Johnson , Sebastian Koch

We investigate extremal graphs related to the game of Cops and Robbers. We focus on graphs where a single cop can catch the robber; such graphs are called cop-win. The capture time of a cop-win graph is the minimum number of moves the cop…

Combinatorics · Mathematics 2019-03-21 David Offner , Kerry Ojakian

We study a game of pursuit and evasion introduced by Seager in 2012, in which a cop searches the robber from outside the graph, using distance queries. A graph on which the cop wins is called locatable. In her original paper, Seager asked…

Combinatorics · Mathematics 2014-02-13 Richard A. B. Johnson , Sebastian Koch

A graph $G$ is said to be ubiquitous, if every graph $\Gamma$ that contains arbitrarily many disjoint $G$-minors automatically contains infinitely many disjoint $G$-minors. The well-known Ubiquity conjecture of Andreae says that every…

It is well-known that in finite graphs, large complete minors/topological minors can be forced by assuming a large average degree. Our aim is to extend this fact to infinite graphs. For this, we generalise the notion of the relative end…

Combinatorics · Mathematics 2011-02-03 Maya Stein , José Zamora

This paper is the last part of a comprehensive survey of a newly emerging field: a topological approach to the study of locally finite graphs that crucially incorporates their ends. Topological arcs and circles, which may pass through ends,…

Algebraic Topology · Mathematics 2010-05-12 Reinhard Diestel , Philipp Sprüssel

We consider the localization game played on graphs, wherein a set of cops attempt to determine the exact location of an invisible robber by exploiting distance probes. The corresponding optimization parameter for a graph $G$ is called the…

Combinatorics · Mathematics 2020-01-27 Anthony Bonato , William B. Kinnersley

Extremal graph theory studies the maximum or minimum number of subgraphs isomorphic to a prescribed graph under given constraints. \textit{Localization} has recently emerged as a framework that refines such problems by assigning extremal…

Combinatorics · Mathematics 2026-03-10 Rajat Adak , L. Sunil Chandran

We highlight new results on the localization number of a graph, a parameter derived from the localization graph searching game. After introducing the game and providing an overview of existing results, we describe recent results on the…

Combinatorics · Mathematics 2021-03-22 Anthony Bonato , Melissa A. Huggan , Trent G. Marbach

The locating chromatic number of a graph is the smallest integer $n$ such that there is a proper $n$-coloring $c$ and every vertex has a unique vector of distances to colors in $c$. We explore the necessary conditions and provide sufficient…

Combinatorics · Mathematics 2023-08-02 Yusuf Hafidh , Devi Imulia Dian Primaskun , Edy Tri Baskoro

There are different definitions of ends in non-locally-finite graphs which are all equivalent in the locally finite case. We prove the compactness of the end-topology that is based on the principle of removing finite sets of vertices and…

Combinatorics · Mathematics 2009-10-31 B. Krön

The randomized online-LOCAL model captures a number of models of computing; it is at least as strong as all of these models: - the classical LOCAL model of distributed graph algorithms, - the quantum version of the LOCAL model, - finitely…

Distributed, Parallel, and Cluster Computing · Computer Science 2024-12-19 Anubhav Dhar , Eli Kujawa , Henrik Lievonen , Augusto Modanese , Mikail Muftuoglu , Jan Studený , Jukka Suomela

The directions of an infinite graph $G$ are a tangle-like description of its ends: they are choice functions that choose compatibly for all finite vertex sets $X\subseteq V(G)$ a component of $G-X$. Although every direction is induced by a…

Combinatorics · Mathematics 2021-01-19 Jan Kurkofka , Ruben Melcher

We systematically study a natural problem in extremal graph theory, to minimize the number of edges in a graph with a fixed number of vertices, subject to a certain local condition: each vertex must be in a copy of a fixed graph $H$. We…

Combinatorics · Mathematics 2020-06-24 Debsoumya Chakraborti , Po-Shen Loh

We consider the Robber Locating Game, where an invisible moving robber tries to evade the pursuit of one or more helicopter cops, who send distance probes from anywhere on the graph. In this paper, we attempt to propose two useful…

Computational Complexity · Computer Science 2023-07-07 Shiqi Pan

We present an order-theoretic approach to the study of countably infinite locally 2-arc-transitive bipartite graphs. Our approach is motivated by techniques developed by Warren and others during the study of cycle-free partial orders. We…

Group Theory · Mathematics 2014-06-09 Robert D. Gray , John K. Truss

We introduce two variations of the cops and robber game on graphs. These games yield two invariants in $\mathbb{Z}_+\cup\{\infty\}$ for any connected graph $\Gamma$, the {weak cop number $\mathsf{wcop}(\Gamma)$} and the {strong cop number…

Combinatorics · Mathematics 2023-06-22 Jonathan Lee , Eduardo Martínez-Pedroza , Juan Felipe Rodríguez-Quinche

We prove an accessibility theorem for finite-index splittings of groups. Given a finitely presented group G there is a number n(G) such that, for every reduced locally finite G-tree T with finitely generated stabilizers, T/G has at most…

Group Theory · Mathematics 2024-04-17 Max Forester , Anthony Martino