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This is a survey paper. We study the Ricci curvature and spectrum of graphs, as well as the exterior forms and deRahm cohomology on graphs.

Combinatorics · Mathematics 2012-04-17 Yong Lin , Shing-Tung Yau

A Riemann-Roch theorem on graph was initiated by M. Baker and S. Norine. In their article [2], a Riemann-Roch theorem on a finite graph with uniform vertex-weight and uniform edge-weight was established and it was suggested a Riemann-Roch…

Combinatorics · Mathematics 2022-01-20 Atsushi Atsuji , Hiroshi Kaneko

The pattern of a matrix M is a (0,1)-matrix which replaces all non-zero entries of M with a 1. There are several contexts in which studying the patterns of orthogonal matrices can be useful. One necessary condition for a matrix to be…

Combinatorics · Mathematics 2007-05-23 J. Richard Lundgren , Simone Severini , Dustin J. Stewart

Graphs are a central object of study in various scientific fields, such as discrete mathematics, theoretical computer science and network science. These graphs are typically studied using combinatorial, algebraic or probabilistic methods,…

Discrete Mathematics · Computer Science 2021-08-19 Karel Devriendt , Piet Van Mieghem

The Heawood graph is a remarkable graph that played a fundamental role in the development of the theory of graph colorings on surfaces in the 19th and 20th centuries. Based on permutahedral tilings, we introduce a generalization of the…

Combinatorics · Mathematics 2023-08-03 Cesar Ceballos , Joseph Doolittle

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

We show that any connected regular graph with $d+1$ distinct eigenvalues and odd-girth $2d+1$ is distance-regular, and in particular that it is a generalized odd graph.

Combinatorics · Mathematics 2012-02-13 Edwin R. van Dam , Willem H. Haemers

We investigate Riemann-Roch theory for directed graphs. The Riemann-Roch criteria of Amini and Manjunath is generalized to all integer lattices orthogonal to some positive vector. Using generalized notions of a $v_0$-reduced divisor and…

Combinatorics · Mathematics 2011-09-26 Arash Asadi , Spencer Backman

A graph G is said to be 1-perfectly orientable (1-p.o. for short) if it admits an orientation such that the out-neighborhood of every vertex is a clique in G. The class of 1-p.o. graphs forms a common generalization of the classes of…

Combinatorics · Mathematics 2016-08-31 Tatiana Romina Hartinger , Martin Milanič

The work provides a brief intuitive overview theory of graph on surfaces. We considers graphs with an additional structure, wich we call discs with ribbons, also known as one-vertex ribbon graphs. And solves the problem (Skopenkov's) about…

Combinatorics · Mathematics 2025-07-03 Tim Berezin

The sandpile group of a graph is a well-studied object that combines ideas from algebraic graph theory, group theory, dynamical systems, and statistical physics. A graph's sandpile group is part of a larger algebraic structure on the graph,…

In this paper, we extend the ideas of graph pebbling to oriented graphs and find a classification for all graphs with fully traversable pebbling assignments that are isomorphic to their assignment graph. We then give some cases in which a…

Combinatorics · Mathematics 2022-03-02 Jared Glassband , Garrison Koch , Sophia Lebiere , Xufei Liu , Evan Sabini

For undirected graphs, the Ricci curvature introduced by Lin-Lu-Yau has been widely studied from various perspectives, especially geometric analysis. In the present paper, we discuss generalization problem of their Ricci curvature for…

Differential Geometry · Mathematics 2020-07-07 Ryunosuke Ozawa , Yohei Sakurai , Taiki Yamada

This article deals with homomorphisms of oriented graphs with respect to push equivalence. Here homomorphisms refer to arc preserving vertex mappings, and push equivalence refers to the equivalence class of orientations of a graph $G$ those…

Combinatorics · Mathematics 2024-10-28 Tapas Das , Pavan P D , Sagnik Sen , S Taruni

A graph is an efficient open (resp.\ closed) domination graph if there exists a subset of vertices whose open (resp.\ closed) neighborhoods partition its vertex set. Graphs that are efficient open as well as efficient closed (shortly EOCD…

Combinatorics · Mathematics 2015-11-09 Sandi Klavzar , Iztok Peterin , Ismael G. Yero

In this paper, we observe graph fractaloids, which are the graph groupoids with fractal property. In particular, we classify them in terms of the spectral data of certain Hilbert space operators, called the radial operators. Based on these…

Mathematical Physics · Physics 2009-02-04 Ilwoo Cho , Palle E. T. Jorgensen

In the branch of mathematics known as graph theory, graphs are considered as a set of points, called vertices, with connections between these points, called edges. The purpose of this paper is to study mappings between two graphs that have…

Combinatorics · Mathematics 2019-03-19 Jeffrey Beyerl , Cameron Sharpe

Graph transformations definable in logic can be described using the notion of transductions. By understanding transductions as a basic embedding mechanism, which captures the possibility of encoding one graph in another graph by means of…

Combinatorics · Mathematics 2025-01-09 Michał Pilipczuk

Given a graph and a representation of its fundamental group, there is a naturally associated twisted adjacency operator. The main result of this article is the fact that these operators behave in a controlled way under graph covering maps.…

Combinatorics · Mathematics 2023-08-22 David Cimasoni , Adrien Kassel

We claim that $M$(atroid) theory may provide a mathematical framework for an underlying description of $M$-theory. Duality is the key symmetry which motivates our proposal. The definition of an oriented matroid in terms of the Farkas…

High Energy Physics - Theory · Physics 2008-11-26 J. A. Nieto