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Extending the well-known star-comb lemma for infinite graphs, we characterise the graphs that do not contain an infinite comb or an infinite star, respectively, attached to a given set of vertices. We offer several characterisations: in…

Combinatorics · Mathematics 2021-08-09 Carl Bürger , Jan Kurkofka

We study {\em generalized graph splines,} introduced by Gilbert, Viel, and the last author. For a large class of rings, we characterize the graphs that only admit constant splines. To do this, we prove that if a graph has a particular type…

Combinatorics · Mathematics 2020-02-12 Katie Anders , Alissa Crans , Briana Foster-Greenwood , Blake Mellor , Julianna Tymoczko

We present an elementary construction of an uncountably chromatic graph without uncountable, infinitely connected subgraphs.

Combinatorics · Mathematics 2024-05-20 Nathan Bowler , Max Pitz

We prove that for any fixed r>=2, the tree-width of graphs not containing K_r as a topological minor (resp. as a subgraph) is bounded by a linear (resp. polynomial) function of their rank-width. We also present refinements of our bounds for…

Combinatorics · Mathematics 2014-03-26 Fedor V. Fomin , Sang-il Oum , Dimitrios M. Thilikos

Local certification consists in assigning labels to the nodes of a network to certify that some given property is satisfied, in such a way that the labels can be checked locally. In the last few years, certification of graph classes…

Distributed, Parallel, and Cluster Computing · Computer Science 2021-09-14 Nicolas Bousquet , Laurent Feuilloley , Théo Pierron

This is the first step of the two steps to enumerate the minimal charts with two crossings. For a label $m$ of a chart $\Gamma$ we denote by $\Gamma_m$ the union of all the edges of label $m$ and their vertices. For a minimal chart $\Gamma$…

Geometric Topology · Mathematics 2018-06-04 Teruo Nagase , Akiko Shima

We show that problems which have finite integer index and satisfy a requirement we call treewidth-bounding admit linear kernels on the class of $H$-topological-minor free graphs, for an arbitrary fixed graph $H$. This builds on earlier…

Data Structures and Algorithms · Computer Science 2012-07-16 Alexander Langer , Felix Reidl , Peter Rossmanith , Somnath Sikdar

We prove that a minor-closed class of graphs has bounded layered pathwidth if and only if some apex-forest is not in the class. This generalises a theorem of Robertson and Seymour, which says that a minor-closed class of graphs has bounded…

Combinatorics · Mathematics 2020-08-03 Vida Dujmović , David Eppstein , Gwenaël Joret , Pat Morin , David R. Wood

AT-free graphs are characterized by vertex elimination orders. We show that these AT-free orders of a graph can be generated in constant amortized time.

Combinatorics · Mathematics 2021-08-20 Jou-Ming Chang , Ton Kloks , Hung-Lung Wang

The celebrated grid exclusion theorem states that for every $h$-vertex planar graph $H$, there is a constant $c_{h}$ such that if a graph $G$ does not contain $H$ as a minor then $G$ has treewidth at most $c_{h}$. We are looking for…

Combinatorics · Mathematics 2015-11-10 Jean-Florent Raymond , Dimitrios M. Thilikos

Among graphs with 13 edges, there are exactly three internally 4-connected graphs which are $Oct^{+}$, cube+e and $ K_{3,3} +v$. A complete characterization of all 4-connected graphs with no $Oct^{+}$-minor is given in [John Maharry, An…

Combinatorics · Mathematics 2023-10-23 Linsong Wei , Yuqi Xu , Weihua Yang , Yunxia Zhang

We extend the notion of a tree graph to sequences of prime graphs which are cycles and edges and name these non-chordal graphs hollow trees. These structures are especially attractive for palindromic Ising models, which mimic a symmetry of…

Methodology · Statistics 2017-04-07 Nanny Wermuth , Giovanni M. Marchetti

In Part I of this series we described three algorithms that construct canonical tree-decompositions of graphs which distinguish all their k-blocks and tangles of order k. We now establish bounds on the number of parts in these…

Combinatorics · Mathematics 2014-04-25 Johannes Carmesin , Reinhard Diestel , Matthias Hamann , Fabian Hundertmark

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

We prove that for every tree $T$ which is not an edge, for almost every graph $G$ which does not contain $T$ as an induced subgraph, $V(G)$ has a partition into $\alpha(T)-1$ parts certifying this fact. Each part induces a graph which is…

Combinatorics · Mathematics 2025-06-03 Bruce Reed , Yelena Yuditsky

We present an algebraic construction of trace-based De Bruijn tori over finite fields, focusing on the nonzero variant that omits the all-zero pattern. The construction arranges nonzero field elements on a toroidal grid using two…

Combinatorics · Mathematics 2025-06-25 Ming Hsuan Kang , Yu Hsuan Hsieh

Using probabilistic methods, we obtain grid-drawings of graphs without crossings with low volume and small aspect ratio. We show that every $D$-degenerate graph on $n$ vertices can be drawn in $[m]^3$ where $m^3 = O(D^2 n\log n)$. In…

Combinatorics · Mathematics 2024-06-18 Jozsef Balogh , Ethan Patrick White

One of the key results in Robertson and Seymour's seminal work on graph minors is the Grid-Minor Theorem (also called the Excluded Grid Theorem). The theorem states that for every grid $H$, every graph whose treewidth is large enough…

Data Structures and Algorithms · Computer Science 2016-08-11 Chandra Chekuri , Julia Chuzhoy

This work provides a structural characterisation of hereditary graph classes that do not contain a star forest, several graphs obtained from star forests by subset complementation, a union of cliques, and the complement of a union of…

Combinatorics · Mathematics 2017-11-09 Aistis Atminas

Given a planar graph G on n vertices and an integer parameter r<n, an r-division of G with few holes is a decomposition of G into O(n/r) regions of size at most r such that each region contains at most a constant number of faces that are…

Discrete Mathematics · Computer Science 2013-05-20 Philip N. Klein , Shay Mozes , Christian Sommer
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