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We study graphs which admit an acyclic orientation that contains an out-branching and in-branching which are arc-disjoint (such an orientation is called {\bf good}). A {\bf 2T-graph} is a graph whose edge set can be decomposed into two…

Combinatorics · Mathematics 2019-12-11 Joergen Bang-Jensen , Matthias Kriesell

It is well-known that concentrators are sparse graphs of high connectivity, which play a key role in the construction of switching networks; and any semi-vertex transitive graph is isomorphic to a bi-coset graph. In this paper, we prove…

Combinatorics · Mathematics 2012-10-23 Xingchao Deng , Kainan Xiang

In a bidirected graph an edge has a direction at each end, so bidirected graphs generalize directed graphs. We generalize the definitions of transitive closure and transitive reduction from directed graphs to bidirected graphs by…

Combinatorics · Mathematics 2021-06-16 Ouahiba Bessouf , Abdelkader Khelladi , Thomas Zaslavsky

A new general all terminal network reliability factorization theorem is stated. We relegate the proof to a forthcoming second part paper.

Probability · Mathematics 2016-03-22 Juan Manuel Burgos , Franco Robledo

Building upon [1], this study aims to introduce fractal geometry into graph theory, and to establish a potential theoretical foundation for complex networks. Specifically, we employ the method of substitution to create and explore…

Dynamical Systems · Mathematics 2024-05-29 Nero Ziyu Li

We introduce a novel definition of curvature for hypergraphs, a natural generalization of graphs, by introducing a multi-marginal optimal transport problem for a naturally defined random walk on the hypergraph. This curvature, termed…

Information Theory · Computer Science 2018-03-26 Shahab Asoodeh , Tingran Gao , James Evans

This work addresses the intrinsic relationship between trees and networks (i.e. graphs). A complete (invertible) mapping is presented which allows trees to be mapped into weighted graphs and then backmapped into the original tree without…

Physics and Society · Physics 2008-08-07 Luciano da Fontoura Costa , Francisco Aparecido Rodrigues

Network motifs are characteristic patterns which occur in the networks essentially more frequently than the other patterns. For five motifs found in S. Itzkovitz, U. Alon, Phys. Rev.~E, 2005, 71, 026117-1, hierarchical random graphs are…

Mathematical Physics · Physics 2015-04-02 Monika Kotorowicz , Yuri Kozitsky

Graph-modification problems, where we modify a graph by adding or deleting vertices or edges or contracting edges to obtain a graph in a {\it simpler} class, is a well-studied optimization problem in all algorithmic paradigms including…

Data Structures and Algorithms · Computer Science 2021-12-24 Ashwin Jacob , Jari J. H. de Kroon , Diptapriyo Majumdar , Venkatesh Raman

Dynamic graphs have emerged as an appropriate model to capture the changing nature of many modern networks, such as peer-to-peer overlays and mobile ad hoc networks. Most of the recent research on dynamic networks has only addressed the…

Data Structures and Algorithms · Computer Science 2011-02-02 Oksana Denysyuk , Luis Rodrigues

We study spreading processes in temporal graphs, i. e., graphs whose connections change over time. These processes naturally model real-world phenomena such as infectious diseases or information flows. More precisely, we investigate how…

Data Structures and Algorithms · Computer Science 2021-07-21 Hendrik Molter , Malte Renken , Philipp Zschoche

Let $W(G)$ be the Wiener index of a graph $G$. We say that a vertex $v \in V(G)$ is a \v{S}olt\'es vertex in $G$ if $W(G - v) = W(G)$, i.e. the Wiener index does not change if the vertex $v$ is removed. In 1991, \v{S}olt\'es posed the…

Combinatorics · Mathematics 2024-06-05 Nino Bašić , Martin Knor , Riste Škrekovski

We propose a generalization of transformer neural network architecture for arbitrary graphs. The original transformer was designed for Natural Language Processing (NLP), which operates on fully connected graphs representing all connections…

Machine Learning · Computer Science 2021-01-26 Vijay Prakash Dwivedi , Xavier Bresson

Learning-based methods for routing have gained significant attention in recent years, both in single-objective and multi-objective contexts. Yet, existing methods are unsuitable for routing on multigraphs, which feature multiple edges with…

Machine Learning · Computer Science 2026-02-23 Filip Rydin , Attila Lischka , Jiaming Wu , Morteza Haghir Chehreghani , Balázs Kulcsár

Girth-regular graphs with equal girth, regular degree and chromatic index are studied for the determination of 1-factorizations with each 1-factor intersecting every girth cycle. Applications to hamiltonian decomposability and to…

Combinatorics · Mathematics 2025-10-15 Italo J. Dejter

Networks constitute efficient tools for assessing universal features of complex systems. In physical contexts, classical as well as quantum, networks are used to describe a wide range of phenomena, such as phase transitions, intricate…

Quantum Physics · Physics 2016-01-22 Jaroslav Novotný , Gernot Alber , Igor Jex

An embedding of a graph on an orientable surface is orientably-regular (or rotary, in an equivalent terminology) if the group of orientation-preserving automorphisms of the embedding is transitive (and hence regular) on incident vertex-edge…

Combinatorics · Mathematics 2023-11-17 Stefan Gyurki , Sona Pavlikova , Jozef Siran

We call a tree $T$ is \emph{even} if every pair of its leaves is joined by a path of even length. Jackson and Yoshimoto~[J. Graph Theory, 2024] conjectured that every $r$-regular nonbipartite connected graph $G$ has a spanning even tree.…

Combinatorics · Mathematics 2024-09-11 Jiangdong Ai , Zhipeng Gao , Xiangzhou Liu , Jun Yue

It has been previously shown by the authors that a directed graph on a linearly ordered set of edges (ordered graph) with adjacent unique source and sink (bipolar digraph) has a unique fully optimal spanning tree, that satisfies a simple…

Combinatorics · Mathematics 2018-07-19 Emeric Gioan , Michel Las Vergnas

In this paper, we characterize a mixed graph $F$ which contains $k$ edge and arc disjoint spanning mixed arborescences $F_{1}, \ldots, F_{k}$, such that for each $v \in V(F)$, the cardinality of $\{i \in [k]: v \text{ is the root of }…

Combinatorics · Mathematics 2022-01-27 Hui Gao , Daqing Yang