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Let S be a closed orientable surface of genus at least two, and let C be an arbitrary (complex) projective structure on S. We show that there is a decomposition of S into pairs of pants and cylinders such that the restriction of C to each…

Geometric Topology · Mathematics 2010-12-30 Shinpei Baba

We present a streamlined exposition of a construction by R. Chen, A. Poulin, R. Tao, and A. Tserunyan, which proves the treeability of equivalence relations generated by any locally-finite Borel graph such that each component is a…

Logic · Mathematics 2025-04-25 Zhaoshen Zhai

We give a proof for sharp estimate for the number of spanning trees using linear algebra and generalize this bound to multigraphs. In addition, we show that this bound is tight for complete graphs. In addition, we give estimates for number…

Combinatorics · Mathematics 2022-12-01 K. V. Chelpanov

We prove that every Peano continuum with uncountably many local cut points is a topological fractal. This extends some recent results and it partially answers a conjecture by Hata. We also discuss the number of mappings which are necessary…

General Topology · Mathematics 2024-05-30 Klára Karasová , Benjamin Vejnar

It was conjectured by Hoffmann-Ostenhof that the edge set of every connected cubic graph can be decomposed into a spanning tree, a matching and a family of cycles. In this paper, we show that this conjecture holds for traceable cubic…

Combinatorics · Mathematics 2016-07-19 F. Abdolhosseini , S. Akbari , H. Hashemi , M. S. Moradian

The famous Gallai's Conjecture states that any connected graph with n vertices has a path decomposition containing at most (n+1)/2 paths. In this note, we explore graphs generated from removing edges from complete graphs. We first provide…

Combinatorics · Mathematics 2022-11-01 Hua Wang , Andrew Zhang

In Chapter 1 we fully characterise pairs of finite graphs which form a gap in the full homomorphism order. This leads to a simple proof of the existence of generalised duality pairs. We also discuss how such results can be carried to…

Combinatorics · Mathematics 2018-01-04 Yangjing Long

Transitivity, the existence of periodic points and positive topological entropy can be used to characterize complexity in dynamical systems. It is known that for graphs that are not trees, for every $\varepsilon>0,$ there exist (complicate)…

Dynamical Systems · Mathematics 2018-07-05 Lluís Alsedà , Liane Bordignon , Jorge Groisman

The presented material is devoted to the equivalent conversion from the vertex graphs to the edge graphs. We suggest that the proved theorems solve the problem of the isomorphism of graphs, the problem of the graph's enumeration with the…

Computational Complexity · Computer Science 2012-10-22 Leonid Malinin , Natalia Malinina

We prove a far-reaching strengthening of Szemer\'edi's regularity lemma for intersection graphs of pseudo-segments. It shows that the vertex set of such a graph can be partitioned into a bounded number of parts of roughly the same size such…

Combinatorics · Mathematics 2023-12-05 Jacob Fox , Janos Pach , Andrew Suk

The 3-decomposition conjecture is wide open. It asserts that every finite connected cubic graph can be decomposed into a spanning tree, a disjoint union of cycles, and a matching. We show that every such decomposition is derived from a…

Combinatorics · Mathematics 2022-02-22 Oliver Bachtler , Irene Heinrich

We survey recent advances in the theory of graph and hypergraph decompositions, with a focus on extremal results involving minimum degree conditions. We also collect a number of intriguing open problems, and formulate new ones.

Combinatorics · Mathematics 2021-06-28 Stefan Glock , Daniela Kühn , Deryk Osthus

We present sweeping line graphs, a generalization of $\Theta$-graphs. We show that these graphs are spanners of the complete graph, as well as of the visibility graph when line segment constraints or polygonal obstacles are considered. Our…

Computational Geometry · Computer Science 2024-01-09 Keenan Lee , André van Renssen

The canonical tree-decomposition theorem, given by Robertson and Seymour in their seminal graph minors series, turns out to be one of the most important tool in structural and algorithmic graph theory. In this paper, we provide the…

Discrete Mathematics · Computer Science 2020-09-29 Archontia C. Giannopoulou , Ken-ichi Kawarabayashi , Stephan Kreutzer , O-joung Kwon

We prove canonical and non-canonical tree-of-tangles theorems for abstract separation systems that are merely structurally submodular. Our results imply all known tree-of-tangles theorems for graphs, matroids and abstract separation systems…

Combinatorics · Mathematics 2025-05-16 Christian Elbracht , Jay Lilian Kneip , Maximilian Teegen

We classify the finite connected-homogeneous digraphs, as well as the infinite such digraphs with precisely one end. This completes the classification of all the locally finite connected-homogeneous digraphs.

Combinatorics · Mathematics 2011-01-13 Matthias Hamann

We investigate which topological spaces can be constructed as topological realisations of higher-rank graphs. We describe equivalence relations on higher-rank graphs for which the quotient is again a higher-rank graph, and show that…

Operator Algebras · Mathematics 2016-06-09 Alex Kumjian , David Pask , Aidan Sims , Michael F. Whittaker

There are many intriguing questions in extremal graph theory that are well-understood in the undirected setting and yet remain elusive for digraphs. A natural instance of such a problem was recently studied by Hons, Klimo\v{s}ov\'{a},…

Combinatorics · Mathematics 2025-05-28 Micha Christoph , Raphael Steiner

The tree of decomposition of a $k$-connected graph by a set $\mathfrak S$ of pairwise independent $k$-vertex cutsets is defined as follows. The vertices of this tree are cutsets of $\mathfrak S$ and parts of decomposition of the graph by…

Combinatorics · Mathematics 2014-05-29 Dmitri Karpov

It was recently proved that every planar graph is a subgraph of the strong product of a path and a graph with bounded treewidth. This paper surveys generalisations of this result for graphs on surfaces, minor-closed classes, various…

Combinatorics · Mathematics 2021-02-18 Zdeněk Dvořák , Tony Huynh , Gwenaël Joret , Chun-Hung Liu , David R. Wood
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