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Zaslavsky proved in 2012 that, up to switching isomorphism, there are six different signed Petersen graphs and that they could be told apart by their chromatic polynomials, by showing that the latter give distinct results when evaluated at…

Combinatorics · Mathematics 2019-04-10 Matthias Beck , Erika Meza , Bryan Nevarez , Alana Shine , Michael Young

Up to switching isomorphism there are six ways to put signs on the edges of the Petersen graph. We prove this by computing switching invariants, especially frustration indices and frustration numbers, switching automorphism groups,…

Combinatorics · Mathematics 2016-10-25 Thomas Zaslavsky

Two signed graphs are called switching isomorphic if one of them is isomorphic to a switching equivalent of the other. To determine the number of switching non-isomorphic signed graphs on a specific graph, we will establish a method based…

Combinatorics · Mathematics 2019-09-17 Yousef Bagheri , Alireza Moghadamfar , Farzaneh Ramezani

A signed graph is a graph where the edges are assigned labels of either "$+$" or "$-$". The sign of a cycle in the graph is the product of the signs of its edges. We equip each signed complete graph with a vector whose entries are the…

Combinatorics · Mathematics 2017-07-03 Alex Schaefer

A signed graph is a graph whose edges are labelled positive or negative. The sign of a circle (cycle, circuit) is the product of the signs of its edges. Most of the essential properties of a signed graph depend on the signs of its circles.…

Combinatorics · Mathematics 2021-06-16 Thomas Zaslavsky

A signed graph is a graph whose edges are signed. In a vertex-signed graph the vertices are signed. The latter is called consistent if the product of signs in every circle is positive. The line graph of a signed graph is naturally…

Combinatorics · Mathematics 2021-06-21 Thomas Zaslavsky

A signed graph is a graph together with an assignment of signs to the edges. A closed walk in a signed graph is said to be positive (negative) if it has an even (odd) number of negative edges, counting repetition. Recognizing the signs of…

Combinatorics · Mathematics 2021-06-16 Reza Naserasr , Eric Sopena , Thomas Zaslavsky

A signed graph is a graph whose edges are given (-1,+1) weights. In such a graph, the sign of a cycle is the product of the signs of its edges. A signed graph is called balanced if its adjacency matrix is similar to the adjacency matrix of…

Combinatorics · Mathematics 2016-10-25 Devlin Mallory , Abigail Raz , Christino Tamon , Thomas Zaslavsky

We give a characterization of when a signed graph $G$ with a pair of distinguished edges $e_1, e_2 \in E(G)$ has the property that all cycles containing both $e_1$ and $e_2$ have the same sign. This answers a question of Zaslavsky.

Combinatorics · Mathematics 2023-06-12 Matt DeVos , Kathryn Nurse

A signed graph is a graph in which each edge is labeled with $+1$ or $-1$. A (proper) vertex coloring of a signed graph is a mapping $\f$ that assigns to each vertex $v\in V(G)$ a color $\f(v)\in \mz$ such that every edge $vw$ of $G$…

Combinatorics · Mathematics 2015-07-17 Thomas Schweser , Michael Stiebitz

A signed complete graph contains both positive and negative Hamiltonian cycles if and only if it also contains both positive and negative triangles. Otherwise, all Hamiltonian cycles are negative if and only if all triangles are negative…

Combinatorics · Mathematics 2025-02-18 Xiyong Yan

A signed graph $(G, \sigma)$ is a graph $G$ along with a function $\sigma: E(G) \to \{+,-\}$. A closed walk of a signed graph is positive (resp., negative) if it has an even (resp., odd) number of negative edges, counting repetitions. A…

Discrete Mathematics · Computer Science 2020-09-28 Julien Bensmail , Sandip Das , Soumen Nandi , Théo Pierron , Sagnik Sen , Eric Sopena

A "signed graph" is a graph $\Gamma$ where the edges are assigned sign labels, either "$+$" or "$-$". The sign of a cycle is the product of the signs of its edges. Let $\mathrm{SpecC}(\Gamma)$ denote the list of lengths of cycles in…

Combinatorics · Mathematics 2021-06-21 Alex Schaefer , Thomas Zaslavsky

A signed graph is a simple graph with two types of edges. Switching a vertex $v$ of a signed graph corresponds to changing the type of each edge incident to $v$. A homomorphism from a signed graph $G$ to another signed graph $H$ is a…

Combinatorics · Mathematics 2020-12-18 Fabien Jacques

A signed bipartite graph G(U, V) is a bipartite graph in which each edge is assigned a positive or a negative sign. The signed degree of a vertex x in G(U, V) is the number of positive edges incident with x less the number of negative edges…

Combinatorics · Mathematics 2007-05-23 S. Pirzada , T. A. Naikoo , F. A. Dar

A signed graph is a graph $G$ associated with a mapping $\sigma: E(G)\to \{-1,+1\}$, denoted by $(G,\sigma)$. A $cycle$ of $(G,\sigma)$ is a connected 2-regular subgraph. A cycle $C$ is $positive$ if it has an even number of negative edges,…

Combinatorics · Mathematics 2018-03-09 Yezhou Wu , Dong Ye

A signed graph is one that features two types of edges: positive and negative. Balanced signed graphs are those in which all cycles contain an even number of positive edges. In the adjacency matrix of a signed graph, entries can be $0$,…

Combinatorics · Mathematics 2024-08-15 Cristian M. Conde , Ezequiel Dratman , Luciano N. Grippo

In a signed graph each edge has a sign, $+1$ or $-1$. We introduce in the present paper a new definition of connection in a signed graph by the existence of both positive and negative chains between vertices. We prove some results and…

Combinatorics · Mathematics 2017-08-08 Ouahiba Bessouf , Abdelkader Khelladi , Thomas Zaslavsky

A signed graph is said to be sign-symmetric if it is switching isomorphic to its negation. Bipartite signed graphs are trivially sign-symmetric. We give new constructions of non-bipartite sign-symmetric signed graphs. Sign-symmetric signed…

Combinatorics · Mathematics 2020-03-24 Ebrahim Ghorbani , Willem H. Haemers , Hamid Reza Maimani , Leila Parsaei Majd

A signed graph is an ordered pair $\Sigma=(G,\sigma),$ where $G=(V,E)$ is the underlying graph of $\Sigma$ with a signature function $\sigma:E\rightarrow \{1,-1\}$. In this article, we define $n^{th}$ power of a signed graph and discuss…

Combinatorics · Mathematics 2020-09-23 Shijin T , Germina K A , Shahul Hameed K
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