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The \emph{segment number} of a planar graph is the smallest number of line segments whose union represents a crossing-free straight-line drawing of the given graph in the plane. The segment number is a measure for the visual complexity of a…

Computational Geometry · Computer Science 2019-09-10 Yoshio Okamoto , Alexander Ravsky , Alexander Wolff

In this draft we prove an interesting structural property related to the problem of computing {\em all the best swap edges} of a {\em tree spanner} in unweighted graphs. Previous papers show that the maximum stretch factor of the tree where…

Discrete Mathematics · Computer Science 2018-07-11 Davide Bilò , Kleitos Papadopoulos

The gonality of a graph measures how difficult it is to move chips around the entirety of a graph according to certain chip-firing rules without introducing debt. In this paper we study the gonality of circulant graphs, a class of…

Treewidth is arguably the most important structural graph parameter leading to algorithmically beneficial graph decompositions. Triggered by a strongly growing interest in temporal networks (graphs where edge sets change over time), we…

Data Structures and Algorithms · Computer Science 2020-04-29 Till Fluschnik , Hendrik Molter , Rolf Niedermeier , Malte Renken , Philipp Zschoche

In this note we study and compare three graph invariants related to the 'compactness' of graph drawing in the plane: the dilation coefficient, defined as the smallest possible quotient between the longest and the shortest edge length; the…

Combinatorics · Mathematics 2010-01-05 Martin Milanic , Tomaz Pisanski , Arjana Zitnik

Tree decompositions of graphs are of fundamental importance in structural and algorithmic graph theory. Planar decompositions generalise tree decompositions by allowing an arbitrary planar graph to index the decomposition. We prove that…

Combinatorics · Mathematics 2007-06-13 David R. Wood , Jan Arne Telle

We obtain several sharp spectral bounds, approximations, and exact values for the isoperimetric number and related edge-expansion parameters of graphs. Our results focus on graph powers and on families of graphs with rich algebraic or…

We give a constructive proof of the fact that the treewidth of a graph $G$ is bounded by a linear function of the separation number of $G$.

Combinatorics · Mathematics 2025-03-24 Hussein Houdrouge , Babak Miraftab , Pat Morin

A tessellation of a graph is a partition of its vertices into vertex disjoint cliques. A tessellation cover of a graph is a set of tessellations that covers all of its edges. The $t$-tessellability problem aims to decide whether there is a…

Discrete Mathematics · Computer Science 2021-06-24 A. Abreu , L. Cunha , T. Fernandes , C. de Figueiredo , L. Kowada , F. Marquezino , D. Posner , R. Portugal

Partitioning a graph using graph separators, and particularly clique separators, are well-known techniques to decompose a graph into smaller units which can be treated independently. It was previously known that the treewidth was bounded…

Discrete Mathematics · Computer Science 2019-09-09 Boi Faltings , Martin Charles Golumbic

In this paper we are concerned with various graph invariants (girth, diameter, expansion constants, eigenvalues of the Laplacian, tree number) and their analogs for weighted graphs -- weighing the graph changes a combinatorial problem to…

Combinatorics · Mathematics 2007-05-23 Dmitry Jakobson , Igor Rivin

There are several notions of gonality for graphs. The divisorial gonality dgon(G) of a graph G is the smallest degree of a divisor of positive rank in the sense of Baker-Norine. The stable gonality sgon(G) of a graph G is the minimum degree…

Combinatorics · Mathematics 2019-04-16 Dion Gijswijt , Harry Smit , Marieke van der Wegen

The structural properties of graphs are usually characterized in terms of invariants, which are functions of graphs that do not depend on the labeling of the nodes. In this paper we study convex graph invariants, which are graph invariants…

Optimization and Control · Mathematics 2012-09-21 Venkat Chandrasekaran , Pablo A. Parrilo , Alan S. Willsky

We consider monotonicity problems for graph searching games. Variants of these games - defined by the type of moves allowed for the players - have been found to be closely connected to graph decompositions and associated width measures such…

Discrete Mathematics · Computer Science 2008-02-18 Stephan Kreutzer , Sebastian Ordyniak

The treewidth is a structural parameter that measures the tree-likeness of a graph. Many algorithmic and combinatorial results are expressed in terms of the treewidth. In this paper, we study the treewidth of outer $k$-planar graphs, that…

Discrete Mathematics · Computer Science 2025-04-24 Oksana Firman , Grzegorz Gutowski , Myroslav Kryven , Yuto Okada , Alexander Wolff

The uniform infinite planar quadrangulation is an infinite random graph embedded in the plane, which is the local limit of uniformly distributed finite quadrangulations with a fixed number of faces. We study asymptotic properties of this…

Probability · Mathematics 2017-01-05 Jean-François Le Gall , Laurent Ménard

Learning generative models for graph-structured data is challenging because graphs are discrete, combinatorial, and the underlying data distribution is invariant to the ordering of nodes. However, most of the existing generative models for…

Machine Learning · Computer Science 2020-03-03 Chenhao Niu , Yang Song , Jiaming Song , Shengjia Zhao , Aditya Grover , Stefano Ermon

In this paper, we define a new construction of completely scrambled 0-dimensional systems using the inverse limit of sequences of directed graph covers. These examples are transitive and are not locally equicontinuous.

Dynamical Systems · Mathematics 2015-09-21 Takashi Shimomura

Computing the crossing number of a graph is one of the most classical problems in computational geometry. Both it and numerous variations of the problem have been studied, and overcoming their frequent computational difficulty is an active…

Computational Geometry · Computer Science 2024-12-18 Thekla Hamm , Fabian Klute , Irene Parada

Twisted graph diagrams are virtual graph diagrams with bars on edges. A bijection between abstract graph diagrams and twisted graph diagrams is constructed. Then a polynomial invariant of Yamada-type is developed which provides a lower…

Geometric Topology · Mathematics 2007-06-20 Jason Uhing