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Circular-arc graphs are graphs that can be represented as intersection graphs of subpaths of a cycle. Interval graphs are graphs that can be represented as intersection graphs of subpaths of a path. Since cycles are locally paths, every…

Combinatorics · Mathematics 2025-12-23 Tara Abrishami , Sandra Albrechtsen , Nathan Bowler , Paul Knappe , Jana Katharina Nickel

Chordal graphs and chordal bigraphs enjoy beautiful characterizations, in terms of forbidden subgraphs, vertex/edge orderings, vertex/edge separating sets, and tree-like representations. In this paper, we introduce chordal signed graphs and…

Combinatorics · Mathematics 2026-01-09 Jing Huang , Ying Ying Ye

Graphs possess exotic features like variable size and absence of natural ordering of the nodes that make them difficult to analyze and compare. To circumvent this problem and learn on graphs, graph feature representation is required. A good…

Machine Learning · Computer Science 2019-12-03 Edouard Pineau

In this work we investigate the chordality of squares and line graph squares of graphs. We prove a sufficient condition for the chordality of squares of graphs not containing induced cycles of length at least five. Moreover, we characterize…

Combinatorics · Mathematics 2017-04-04 Robert Scheidweiler , Sebastian Wiederrecht

A strict confluent (SC) graph drawing is a drawing of a graph with vertices as points in the plane, where vertex adjacencies are represented not by individual curves but rather by unique smooth paths through a planar system of junctions and…

Computational Geometry · Computer Science 2019-08-16 Henry Förster , Robert Ganian , Fabian Klute , Martin Nöllenburg

We introduce a non-backtracking Laplace operator for graphs and we investigate its spectral properties. With the use of both theoretical and computational techniques, we show that the spectrum of this operator captures several structural…

Spectral Theory · Mathematics 2023-06-13 Jürgen Jost , Raffaella Mulas , Leo Torres

It is known that non-isomorphic strongly regular graphs with the same parameters must be cospectral (have the same eigenvalues). In this paper, we investigate whether the spectra of higher order Laplacians associated with these graphs can…

Combinatorics · Mathematics 2025-08-11 Sebastian M. Cioabă , Krystal Guo , Chunxu Ji , Mutasim Mim

We identify all minimal chordal graphs that are not circular-arc graphs, thereby resolving one of ``the main open problems'' concerning the structures of circular-arc graphs as posed by Dur{\'{a}}n, Grippo, and Safe in 2011. The problem had…

Combinatorics · Mathematics 2025-02-25 Yixin Cao , Tomasz Krawczyk

We characterize when the spectral variation of the signed Laplacian matrices is integral after a new edge is added to a signed graph. As an application, for every fixed signed complete graph, we fully characterize the class of signed graphs…

Combinatorics · Mathematics 2024-01-08 Jungho Ahn , Cheolwon Heo , Sunyo Moon

Chordal graphs can be used to encode dependency models that are representable by both directed acyclic and undirected graphs. This paper discusses a very simple and efficient algorithm to learn the chordal structure of a probabilistic model…

Machine Learning · Computer Science 2012-06-18 Vincent Auvray , Louis Wehenkel

The concept of graph powers has been extensively studied in graph theory. Analogous to graph powers, Chandran et al. [3] introduced the notion of bipartite powers for bipartite graphs. In this paper, we show that the class of interval…

Combinatorics · Mathematics 2025-09-29 Indrajit Paul , Ashok Kumar Das

This paper is devoted to the investigation of the spectral theory and dynamical properties of periodic graphs which are not locally finite but carry non-negative, symmetric and summable edge weights. These graphs are shown to exhibit rather…

Spectral Theory · Mathematics 2025-06-25 Joachim Kerner , Olaf Post , Mostafa Sabri , Matthias Täufer

We examine indivisibility for classes of graphs. We show that the class of hereditarily $\alpha$-sparse graphs is indivisible if and only if $\alpha > 2$. Additionally, we show that the following classes of graphs are indivisible: perfect…

Combinatorics · Mathematics 2025-04-09 Vince Guingona , Felix Nusbaum , Zain Padamsee , Miriam Parnes , Christian Pippin , Ava Zinman

Graph convexity spaces have been studied in many contexts. In particular, some studies are devoted to determine if a graph equipped with a convexity space is a {\em convex geometry}. It is well known that chordal and Ptolemaic graphs can be…

Combinatorics · Mathematics 2022-03-14 Marisa Gutierrez , Fábio Protti , Silvia B. Tondato

A strong clique in a graph is a clique intersecting every maximal independent set. We study the computational complexity of six algorithmic decision problems related to strong cliques in graphs and almost completely determine their…

Combinatorics · Mathematics 2018-08-28 Ademir Hujdurović , Martin Milanič , Bernard Ries

We consider a non self-adjoint Laplacian on a directed graph with non symmetric edge weights. We give necessary conditions for this Laplacian to be sectorial. We introduce a special self-adjoint operator and compare its essential spectrum…

Spectral Theory · Mathematics 2018-01-08 Colette Anné , Marwa Balti , Nabila Torki-Hamza

Grid intersection graphs are the intersection graphs of vertical and horizontal segments in the plane. When the bottom and respectively left endpoints of the vertical and horizontals segments belong to a line with negative slope, the graph…

Discrete Mathematics · Computer Science 2022-01-27 Irena Rusu

Given a property (graph class) $\Pi$, a graph $G$, and an integer $k$, the \emph{$\Pi$-completion} problem consists in deciding whether we can turn $G$ into a graph with the property $\Pi$ by adding at most $k$ edges to $G$. The…

A linear-interval order is the intersection of a linear order and an interval order. For this class of orders, several structural results have been known. This paper introduces a new subclass of linear-interval orders. We call a partial…

Discrete Mathematics · Computer Science 2021-05-11 Asahi Takaoka

There is an extensive literature on dynamic algorithms for a large number of graph theoretic problems, particularly for all varieties of shortest path problems. Germane to this paper are a number fully dynamic algorithms that are known for…

Data Structures and Algorithms · Computer Science 2020-02-19 Md. Zamilur Rahman , Asish Mukhopadhyay