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A directed hypergraph (dihypergraph) consists of a set of vertices and a set of hyperarcs, where each hyperarc is partitioned into a head and a tail. Directed hypergraphs are useful in many applications, including the study of chemical…

Combinatorics · Mathematics 2026-04-14 Catherine Greenhill , Tamás Makai

The study of hypergraphs has received a lot of attention over the past few years, however up until recently there has been no interest in systems where higher order interactions are not undirected. In this article we introduce the notion of…

Mathematical Physics · Physics 2024-08-28 Gonzalo Contreras-Aso , Regino Criado , Miguel Romance

A signed graph is a graph whose edges are labeled either positive or negative. Corresponding to the two signed distance matrices defined for signed graphs, we define two signed distance laplacian matrices. We characterize balance in signed…

Combinatorics · Mathematics 2020-10-12 Roshni T Roy , K A Germina , K Shahul Hameed , Thomas Zaslavsky

A metrized graph is a compact singular 1-manifold endowed with a metric. A given metrized graph can be modelled by a family of weighted combinatorial graphs. If one chooses a sequence of models from this family such that the vertices become…

Classical Analysis and ODEs · Mathematics 2007-05-23 X. W. C. Faber

The $\alpha$-Hermitian adjacency matrix $H_\alpha$ of a mixed graph $X$ has been recently introduced. It is a generalization of the adjacency matrix of unoriented graphs. In this paper, we consider a special case of the complex number…

Combinatorics · Mathematics 2022-05-26 Omar Alomari , Mohammad Abudayah , Manal Ghanem

Given an undirected graph, one can assign directions to each of the edges of the graph, thus orienting the graph. To be as egalitarian as possible, one may wish to find an orientation such that no vertex is unfairly hit with too many arcs…

Discrete Mathematics · Computer Science 2017-11-10 Glencora Borradaile , Jennifer Iglesias , Theresa Migler , Antonio Ochoa , Gordon Wilfong , Lisa Zhang

A mixed graph is a graph with some directed edges and some undirected edges. We introduce the notion of mixed matroids as a generalization of mixed graphs. A mixed matroid can be viewed as an oriented matroid in which the signs over a fixed…

Combinatorics · Mathematics 2007-05-23 J. Orestes Cerdeira , Raul Cordovil

A matrix-weighted graph is an undirected graph with a $k\times k$ positive semidefinite matrix assigned to each edge. There are natural generalizations of the Laplacian and adjacency matrices for such graphs. These matrices can be used to…

Combinatorics · Mathematics 2020-09-28 Jakob Hansen

A hypergraph is a $T_0$-hypergraph if for every two different vertices of the hypergraph there exists an edge containing one of the vertices and not containing the other. A general method for the enumeration of certain classes of…

Combinatorics · Mathematics 2014-11-18 Goran Kilibarda , Vladeta Jovović

An ordered hypergraph is a hypergraph whose vertex set is linearly ordered, and a convex geometric hypergraph is a hypergraph whose vertex set is cyclically ordered. Extremal problems for ordered and convex geometric graphs have a rich…

Combinatorics · Mathematics 2019-06-12 Zoltán F\" uredi , Tao Jiang , Alexandr Kostochka , Dhruv Mubayi , Jacques Verstraëte

A signed directed graph is a graph with sign and direction information on the edges. Even though signed directed graphs are more informative than unsigned or undirected graphs, they are more complicated to analyze and have received less…

Machine Learning · Computer Science 2023-02-17 Taewook Ko , Chong-Kwon Kim

In this study, we explore the substructures of a hypergraph that lead us to linearly dependent rows (or columns) in the incidence matrix of the hypergraph. These substructures are closely related to the spectra of various hypergraph…

Combinatorics · Mathematics 2024-04-30 Samiron Parui

This paper introduces gradient, adjoint, and $p$-Laplacian definitions for oriented hypergraphs as well as differential and averaging operators for unoriented hypergraphs. These definitions are used to define gradient flows in the form of…

Social and Information Networks · Computer Science 2024-05-06 Ariane Fazeny , Daniel Tenbrinck , Kseniia Lukin , Martin Burger

Hypergraphs serve as an effective tool widely adopted to characterize higher-order interactions in complex systems. The most intuitive and commonly used mathematical instrument for representing a hypergraph is the incidence matrix, in which…

Social and Information Networks · Computer Science 2026-04-22 Junhao Bian , Yilin Bi , Tao Zhou

In the theory of line graphs of undirected graphs there exists an important theorem linking the incidence matrix of the root graph to the adjacency matrix of its line graph. For directed or mixed graphs, however, the exists no analogous…

Combinatorics · Mathematics 2022-05-12 Mohammad Abudayah , Omar Alomari , Torsten Sander

In data science, hypergraphs are natural models for data exhibiting multi-way relations, whereas graphs only capture pairwise. Nonetheless, many proposed hypergraph neural networks effectively reduce hypergraphs to undirected graphs via…

Machine Learning · Computer Science 2025-04-18 Tatyana Benko , Martin Buck , Ilya Amburg , Stephen J. Young , Sinan G. Aksoy

A labelling of a graph is an assignment of labels to its vertex or edge sets (or both), subject to certain conditions, a well established concept. A labelling of a graph G of order n is termed a numbering when the set of integers {1,...,n}…

Combinatorics · Mathematics 2023-06-06 Les Foulds , Humberto J. Longo

Given a digraph, an ordering of its vertices defines a backedge graph, namely the undirected graph whose edges correspond to the arcs pointing backwards with respect to the order. The degreewidth of a digraph is the minimum over all…

Combinatorics · Mathematics 2026-04-15 Pierre Aboulker , Nacim Oijid , Robin Petit , Mathis Rocton , Christopher-Lloyd Simon

An {\em ordered $r$-graph} is an $r$-uniform hypergraph whose vertex set is linearly ordered. Given $2\leq k\leq r$, an ordered $r$-graph $H$ is {\em interval} $k$-{\em partite} if there exist at least $k$ disjoint intervals in the ordering…

Combinatorics · Mathematics 2020-04-13 Zoltán F\" uredi , Tao Jiang , Alexandr Kostochka , Dhruv Mubayi , Jacques Verstraëte

The paper focuses on two problems: (i) how to orient the edges of an undirected graph in order to maximize the number of ordered vertex pairs (x,y) such that there is a directed path from x to y, and (ii) how to orient the edges so as to…

Data Structures and Algorithms · Computer Science 2015-06-02 S. L. Hakimi , E. Schmeichel , Neal E. Young