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Using the definition of colouring of $2$-edge-coloured graphs derived from $2$-edge-coloured graph homomorphism, we extend the definition of chromatic polynomial to $2$-edge-coloured graphs. We find closed forms for the first three…

Combinatorics · Mathematics 2020-07-28 I. Beaton , D. Cox , C. Duffy , N. Zolkavich

We introduce a new notation for representing labeled regular bipartite graphs of arbitrary degree. Several enumeration problems for labeled and unlabeled regular bipartite graphs have been introduced. A general algorithm for enumerating all…

Discrete Mathematics · Computer Science 2015-12-31 Vivek S. Nittoor

A \emph{geometric graph} is a graph whose vertex set is a set of points in general position in the plane, and its edges are straight line segments joining these points. We show that for every integer $k \ge 2$, there exists a constat $c>0$…

Computational Geometry · Computer Science 2023-11-01 Ruy Fabila-Monroy

The $k$-coprime graph of order $n$ is the graph with vertex set $\{k, k+1, \ldots, k+n-1\}$ in which two vertices are adjacent if and only if they are coprime. We characterize Hamiltonian $k$-coprime graphs. As a particular case, two…

Combinatorics · Mathematics 2020-08-10 M. H. Bani Mostafa A. , Ebrahim Ghorbani

A graph automorphism is a bijective mapping of the vertices that preserves adjacent vertices. A vertex determining set of a graph is a set of vertices such that the only automorphism that fixes those vertices is the identity. The size of a…

Combinatorics · Mathematics 2024-06-12 Sean McAvoy , Sally Cockburn

The $k$-dominating graph $D_k(G)$ of a graph $G$ is defined on the vertex set consisting of dominating sets of $G$ with cardinality at most $k$, two such sets being adjacent if they differ by either adding or deleting a single vertex. A…

Combinatorics · Mathematics 2016-04-26 Saeid Alikhani , Davood Fatehi , Sandi Klavžar

Drawings of non-planar graphs always result in edge crossings. When there are many edges crossing at small angles, it is often difficult to follow these edges, because of the multiple visual paths resulted from the crossings that slow down…

Discrete Mathematics · Computer Science 2014-09-02 Yifan Hu , Lei Shi

Regular colored graphs are dual representations of pure colored D-dimensional complexes. These graphs can be classified with respect to an integer, their degree, much like maps are characterized by the genus. We analyse the structure of…

Combinatorics · Mathematics 2016-02-02 Razvan Gurau , Gilles Schaeffer

The domination polynomial of a graph is the polynomial whose coefficients count the number of dominating sets of each cardinality. A recent question asks which graphs are uniquely determined (up to isomorphism) by their domination…

Combinatorics · Mathematics 2013-04-03 Barbara M. Anthony , Michael E. Picollelli

A distinguishing colouring of a graph is a colouring of the vertex set such that no non-trivial automorphism preserves the colouring. Tucker conjectured that if every non-trivial automorphism of a locally finite graph moves infinitely many…

Combinatorics · Mathematics 2015-04-30 Florian Lehner , Rögnvaldur G. Möller

Counting dominating sets in a graph $G$ is closely related to the neighborhood complex of $G$. We exploit this relation to prove that the number of dominating sets $d(G)$ of a graph is determined by the number of complete bipartite…

Combinatorics · Mathematics 2017-01-13 Irene Heinrich , Peter Tittmann

A mixed graph is, informally, an object obtained from a simple undirected graph by choosing an orientation for a subset of its edges. A mixed graph is $(m, n)$-coloured if each edge is assigned one of $m \geq 0$ colours, and each arc is…

Combinatorics · Mathematics 2025-01-15 Gary MacGillivray , Shahla Nasserasr , Feiran Yang

For a flexible labeling of a graph, it is possible to construct infinitely many non-equivalent realizations keeping the distances of connected points constant. We give a combinatorial characterization of graphs that have flexible labelings.…

Combinatorics · Mathematics 2019-09-17 Georg Grasegger , Jan Legerský , Josef Schicho

Using the theory of combinatorial species, we compute the cycle index for bipartite graphs, which we use to count unlabeled bipartite graphs and bipartite blocks.

Combinatorics · Mathematics 2015-09-14 Andrew Gainer-Dewar , Ira M. Gessel

We recall several known results about minimally 2-connected graphs, and show that they all follow from a decomposition theorem. Starting from an analogy with critically 2-connected graphs, we give structural characterizations of the classes…

Discrete Mathematics · Computer Science 2016-03-27 Pierre Aboulker , Marko Radovanović , Nicolas Trotignon , Kristina Vušković

We compute the distance-dependent two-point function of vertex-bicolored planar maps, i.e., maps whose vertices are colored in black and white so that no adjacent vertices have the same color. By distance-dependent two-point function, we…

Combinatorics · Mathematics 2015-12-02 Éric Fusy , Emmanuel Guitter

We examine $t$-colourings of oriented graphs in which, for a fixed integer $k \geq 1$, vertices joined by a directed path of length at most $k$ must be assigned different colours. A homomorphism model that extends the ideas of Sherk for the…

Discrete Mathematics · Computer Science 2023-06-22 Christopher Duffy , Gary MacGillivray , Éric Sopena

We study biplane graphs drawn on a finite planar point set $S$ in general position. This is the family of geometric graphs whose vertex set is $S$ and can be decomposed into two plane graphs. We show that two maximal biplane graphs---in the…

Computational Geometry · Computer Science 2017-08-10 Alfredo García , Ferran Hurtado , Matias Korman , Inês Matos , Maria Saumell , Rodrigo I. Silveira , Javier Tejel , Csaba D. Tóth

A well-known combinatorial theorem says that a set of n non-collinear points in the plane determines at least n distinct lines. Chen and Chv\'atal conjectured that this theorem extends to metric spaces, with an appropriated definition of…

Combinatorics · Mathematics 2016-06-21 Pierre Aboulker , Martin Matamala , Paul Rochet , Jose Zamora

In the past decades, graphs that are determined by their spectrum have received more attention, since they have been applied to several fields, such as randomized algorithms, combinatorial optimization problems and machine learning. An…

Combinatorics · Mathematics 2018-06-27 Ali Zeydi Abdian , Afshin Behmaram , Gholam Hossein Fath-Tabar