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A digraph is connected-homogeneous if any isomorphism between finite connected induced subdigraphs extends to an automorphism of the digraph. We consider locally-finite connected-homogeneous digraphs with more than one end. In the case that…

Combinatorics · Mathematics 2010-11-30 Robert Gray , Rognvaldur G. Moller

We prove that if a graph has a tree-decomposition of width at most w, then it has a tree-decomposition of width at most w with certain desirable properties. We will use this result in a subsequent paper to show that every 2-connected graph…

Combinatorics · Mathematics 2018-04-17 Thanh N. Dang , Robin Thomas

This paper studies graphs that have two tree decompositions with the property that every bag from the first decomposition has a bounded-size intersection with every bag from the second decomposition. We show that every graph in each of the…

Combinatorics · Mathematics 2018-05-21 Vida Dujmović , Gwenaël Joret , Pat Morin , Sergey Norin , David R. Wood

As an extension of a classical tree-partition problem, we consider decompositions of graphs into edge-disjoint (rooted-)trees with an additional matroid constraint. Specifically, suppose we are given a graph $G=(V,E)$, a multiset…

Combinatorics · Mathematics 2011-09-06 Naoki Katoh , Shin-ichi Tanigawa

We present a canonical way to decompose finite graphs into highly connected local parts. The decomposition depends only on an integer parameter whose choice sets the intended degree of locality. The global structure of the graph, as…

Combinatorics · Mathematics 2025-07-01 Reinhard Diestel , Raphael W. Jacobs , Paul Knappe , Jan Kurkofka

Carmesin has extended Robertson and Seymour's tree-of-tangles theorem to the infinite tangles of locally finite infinite graphs. We extend it further to the infinite tangles of all infinite graphs. Our result has a number of applications…

Combinatorics · Mathematics 2021-01-20 Ann-Kathrin Elm , Jan Kurkofka

We provide a finite equational presentation of graphs of treewidth at most three, solving an instanceof an open problem by Courcelle and Engelfriet. We use a syntax generalising series-parallel expressions, denoting graphs with a small…

Logic in Computer Science · Computer Science 2025-01-23 Amina Doumane , Samuel Humeau , Damien Pous

The Tree Decomposition Conjecture by Bar\'at and Thomassen states that for every tree $T$ there exists a natural number $k(T)$ such that the following holds: If $G$ is a $k(T)$-edge-connected simple graph with size divisible by the size of…

Combinatorics · Mathematics 2016-03-02 Martin Merker

Let $F=\{H_1,...,H_k\}$ be a family of graphs. A graph $G$ with $m$ edges is called {\em totally $F$-decomposable} if for {\em every} linear combination of the form $\alpha_1 e(H_1) + ... + \alpha_k e(H_k) = m$ where each $\alpha_i$ is a…

Combinatorics · Mathematics 2007-05-23 Raphael Yuster

In a series of three papers we develop an end space theory for digraphs. Here in the third paper we introduce a concept of depth-first search trees in infinite digraphs, which we call normal spanning arborescences. We show that normal…

Combinatorics · Mathematics 2020-09-08 Carl Bürger , Ruben Melcher

We generalise structure tree theory, which is based on removing finitely many edges, to removing finitely many vertices. This gives a significant generalization of Tutte's tree decomposition of 2-connected graphs into 3-connected blocks.…

Group Theory · Mathematics 2015-01-05 M. J. Dunwoody , B. Krön

The aim of this chapter is to provide an adequate graph theoretic framework for the description of periodic bifurcations which have recently been discovered in descendant trees of finite p-groups. The graph theoretic concepts of rooted…

Group Theory · Mathematics 2017-01-30 Daniel C. Mayer

We show that an arbitrary infinite graph can be compactified by its ${\aleph_0}$-tangles in much the same way as the ends of a locally finite graph compactify it in its Freudenthal compactification. In general, the ends then appear as a…

Combinatorics · Mathematics 2021-03-02 Reinhard Diestel

Graph decompositions are the natural generalisation of tree decompositions where the decomposition tree is replaced by a genuine graph. Recently they found theoretical applications in the theory of sparsity, topological graph theory,…

Discrete Mathematics · Computer Science 2023-12-20 Johannes Carmesin , Sarah Frenkel

In 1985, Golumbic and Scheinerman established an equivalence between comparability graphs and containment graphs, graphs whose vertices represent sets, with edges indicating set containment. A few years earlier, McMorris and Zaslavsky…

Combinatorics · Mathematics 2025-03-31 Ketai Chen , Jared DeLeo , Owen Henderschedt

In this article we generalize the theory of subgroup graphs of subgroups of free groups to finite index subgroups $H$ of finitely generated groups $G$. We study and prove various properties of $H$ in relation to its subgroup graph…

Group Theory · Mathematics 2016-03-23 Cora Welsch

Diestel and K\"uhn proved that the topological ends of an infinite graph are precisely its undominated graph ends, yielding a canonical embedding of the space of topological ends into the space of graph ends. For edge-ends, introduced by…

Combinatorics · Mathematics 2026-02-27 Leandro Aurichi , Paulo Magalhães Júnior , Guilherme Eduardo Pinto

Treewidth is a graph parameter that plays a fundamental role in several structural and algorithmic results. We study the problem of decomposing a given graph $G$ into node-disjoint subgraphs, where each subgraph has sufficiently large…

Data Structures and Algorithms · Computer Science 2013-04-08 Chandra Chekuri , Julia Chuzhoy

Treewidth is a parameter that emerged from the study of minor closed classes of graphs (i.e. classes closed under vertex and edge deletion, and edge contraction). It in some sense describes the global structure of a graph. Roughly, a graph…

Combinatorics · Mathematics 2022-02-02 Tara Abrishami , Maria Chudnovsky , Kristina Vušković

A finite group is called $\psi$-divisible iff $\psi(H)|\psi(G)$ for any subgroup $H$ of a finite group $G$. Here, $\psi(G)$ is the sum of element orders of $G$. For now, the only known examples of such groups are the cyclic ones of…

Group Theory · Mathematics 2022-03-02 Mihai-Silviu Lazorec