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Extending the work of Godsil and others, we investigate the notion of the inverse of a graph (specifically, of bipartite graphs with a unique perfect matching). We provide a concise necessary and sufficient condition for the invertibility…

Combinatorics · Mathematics 2011-08-19 Cam McLeman , Erin McNicholas

A self-contained graph is an infinite graph which is isomorphic to one of its proper induced subgraphs. In this paper, these graphs are studied by presenting some examples and defining some of their sub-structures such as removable…

Combinatorics · Mathematics 2016-11-04 Mohammad Hadi Shekarriz , Madjid Mirzavaziri

We call a finite undirected graph minimally k-matchable if it has at least k distinct perfect matchings but deleting any edge results in a graph which has not. An odd subdivision of some graph G is any graph obtained by replacing every edge…

Combinatorics · Mathematics 2016-08-05 Gasper Fijavz , Matthias Kriesell

In this work we consider temporal graphs, i.e. graphs, each edge of which is assigned a set of discrete time-labels drawn from a set of integers. The labels of an edge indicate the discrete moments in time at which the edge is available. We…

Data Structures and Algorithms · Computer Science 2013-10-30 Paul G. Spirakis , Eleni Ch. Akrida

Temporal graphs are graphs whose topology is subject to discrete changes over time. Given a static underlying graph $G$, a temporal graph is represented by assigning a set of integer time-labels to every edge $e$ of $G$, indicating the…

Discrete Mathematics · Computer Science 2020-09-30 George B. Mertzios , Hendrik Molter , Rolf Niedermeier , Viktor Zamaraev , Philipp Zschoche

We show that the only random orderings of finite graphs that are invariant under isomorphism and induced subgraph are the uniform random orderings. We show how this implies the unique ergodicity of the automorphism group of the random…

Dynamical Systems · Mathematics 2018-09-10 Omer Angel , Alexander S. Kechris , Russell Lyons

A graph $G$ is called interval colorable if it has a proper edge coloring with colors $1,2,3,\dots$ such that the colors of the edges incident to every vertex of $G$ form an interval of integers. Not all graphs are interval colorable; in…

Combinatorics · Mathematics 2021-06-08 Armen S. Asratian , Carl Johan Casselgren , Petros A. Petrosyan

Diophantine tuples are of ancient and modern interest, with a huge literature. In this paper we study Diophantine graphs, i.e., finite graphs whose vertices are distinct positive integers, and two vertices are linked by an edge if and only…

Number Theory · Mathematics 2024-10-29 Gergő Batta , Lajos Hajdu , András Pongrácz

In an earlier work, finite groups whose power graphs are minimally edge connected have been classified. In this article, first we obtain a necessary and sufficient condition for an arbitrary graph to be minimally edge connected.…

Group Theory · Mathematics 2024-08-21 Parveen , Manisha , Jitender Kumar

In this paper, we investigate the ratio of the numbers of odd and even cycles in outerplanar graphs. We verify that the ratio generally diverges to infinity as the order of a graph diverges to infinity. We also give sharp estimations of the…

Combinatorics · Mathematics 2021-05-07 Akihiro Higashitani , Naoki Matsumoto

A proper edge-coloring of a graph is an interval coloring if the labels on the edges incident to any vertex form an interval of consecutive integers. Interval thickness s(G) of a graph G is the smallest number of interval colorable graphs…

Combinatorics · Mathematics 2022-05-13 Maria Axenovich , Michael Zheng

We study the question of whether, for a given class of finite graphs, one can define, for each graph of the class, a linear ordering in monadic second-order logic, possibly with the help of monadic parameters. We consider two variants of…

Logic in Computer Science · Computer Science 2015-07-01 Achim Blumensath , Bruno Courcelle

We exhibit an analogy between the problem of pushing forward measurable sets under measure preserving maps and linear relaxations in combinatorialoptimization. We show how invariance of hyperfiniteness of graphings under local isomorphism…

Combinatorics · Mathematics 2021-02-17 László Lovász

We give a sufficient condition on totally disconnected topological graphs such that their associated topological graph algebras are purely infinite.

Operator Algebras · Mathematics 2017-03-31 Hui Li

We show that the groupoids of two directed graphs are isomorphic if and only if the two graphs are orbit equivalent by an orbit equivalence that preserves isolated eventually periodic points. We also give a complete description of the…

Dynamical Systems · Mathematics 2018-10-08 Toke Meier Carlsen , Marius Lie Winger

We introduce a reducibility on classes of structures, essentially a uniform enumeration reducibility. This reducibility is inspired by the Friedman-Stanley paper on using Borel reductions to compare classes of countable structures. This…

Logic · Mathematics 2008-03-25 Wesley Calvert , Desmond Cummins , Sara Miller , Julia F. Knight

The interplay between groups and graphs have been the most famous and productive area of algebraic graph theory. In this paper, we introduce and study the graphs whose vertex set is group G such that two distinct vertices a and b having…

Combinatorics · Mathematics 2019-01-01 Shafiq Ur Rehman , Abdul Qudair Baig , Muhammad Imran , Zia Ullah Khan

In this note we prove that every closed graph $G$ is up to isomorphism a proper interval graph. As a consequence we obtain that there exist linear-time algorithms for closed graph recognition.

Combinatorics · Mathematics 2012-11-27 Marilena Crupi , Giancarlo Rinaldo

A graph is an opposition graph, respectively, a coalition graph, if it admits an acyclic orientation which puts the two end-edges of every chordless 4-vertex path in opposition, respectively, in the same direction. Opposition and coalition…

Discrete Mathematics · Computer Science 2015-07-03 Van Bang Le , Thomas Podelleck

Consider a family of graphs having a fixed girth and a large size. We give an optimal lower asymptotic bound on the number of even cycles of any constant length, as the order of the graphs tends to infinity.

Combinatorics · Mathematics 2016-03-31 József Solymosi , Ching Wong