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We study a class of directed random graphs. In these graphs, the interval [0,x] is the vertex set, and from each y\in [0,x], directed links are drawn to points in the interval (y,x] which are chosen uniformly with density one. We analyze…

Probability · Mathematics 2012-10-31 Yoshiaki Itoh , P. L. Krapivsky

A digraph $D$ is an oriented graph if $D$ does not have a pair of opposite arcs. The degree of a vertex $v$ of $D$ is the sum of the in-degree and out-degree of $v.$ Let $fvs(D)$ be the minimum number of vertices whose deletion from $D$…

Combinatorics · Mathematics 2025-12-02 Jiangdong Ai , Gregory Gutin , Xiangzhou Liu , Anders Yeo , Yacong Zhou

For a graph $G$ and $p\in [0,1]$, let $G_p$ arise from $G$ by deleting every edge mutually independently with probability $1-p$. The random graph model $(K_n)_p$ is certainly the most investigated random graph model and also known as the…

Combinatorics · Mathematics 2015-12-16 Stefan Ehard , Felix Joos

The reverse degree distance is a connected graph invariant closely related to the degree distance proposed in mathematical chemistry. We determine the unicyclic graphs of given girth, number of pendant vertices and maximum degree,…

Combinatorics · Mathematics 2011-07-13 Zhibin Du , Bo Zhou

We describe the structure of those graphs that have largest spectral radius in the class of all connected graphs with a given degree sequence. We show that in such a graph the degree sequence is non-increasing with respect to an ordering of…

Combinatorics · Mathematics 2008-10-07 Tuerker Biyikoglu , Josef Leydold

We study distance properties of a general class of random directed acyclic graphs (DAGs). In a DAG, many natural notions of distance are possible, for there exists multiple paths between pairs of nodes. The distance of interest for circuits…

Probability · Mathematics 2012-11-12 Nicolas Broutin , Omar Fawzi

Let $G$ be a graph each edge $e$ of which is given a length $\ell(e)$. This naturally induces a distance $d_\ell(x,y)$ between any two vertices $x,y$, and we let $\ell-TOP$ denote the completion of the corresponding metric space. It turns…

Combinatorics · Mathematics 2009-12-14 Agelos Georgakopoulos

In this paper we discuss reconstruction problems for graphs. We develop some new ideas like isomorphic extension of isomorphic graphs, partitioning of vertex sets into sets of equivalent points, subdeck property, etc. and develop an…

General Mathematics · Mathematics 2011-10-21 Dhananjay P. Mehendale

We define direct sums and a corresponding notion of connectedness for graph limits. Every graph limit has a unique decomposition as a direct sum of connected components. As is well-known, graph limits may be represented by symmetric…

Combinatorics · Mathematics 2008-04-10 Svante Janson

Entanglement is a complexity measure of digraphs that origins in fixed-point logics. Its combinatorial purpose is to measure the nested depth of cycles in digraphs. We address the problem of characterizing the structure of graphs of…

Computer Science and Game Theory · Computer Science 2009-04-13 Walid Belkhir

If a vertex in a graph can be deleted without affecting distances among the other vertices, we shall say it is distance-redundant. Graphs with all, some or no such vertices are discussed. (The latter class was termed distance-critical by…

Combinatorics · Mathematics 2024-03-26 Andrew Steane

A consistent path system in a graph $G$ is an intersection-closed collection of paths, with exactly one path between any two vertices in $G$. We call $G$ metrizable if every consistent path system in it is the system of geodesic paths…

Combinatorics · Mathematics 2023-11-17 Maria Chudnovsky , Daniel Cizma , Nati Linial

This is an expository paper. A $1$-cycle in a graph is a set $C$ of edges such that every vertex is contained in an even number of edges from $C$. E.g., a cycle in the sense of graph theory is a $1$-cycle, but not vice versa. It is easy to…

History and Overview · Mathematics 2024-07-24 E. Alkin , S. Dzhenzher , O. Nikitenko , A. Skopenkov , A. Voropaev

In this paper we propose and study a new structural invariant for graphs, called distance-unbalanced\-ness, as a measure of how much a graph is (un)balanced in terms of distances. Explicit formulas are presented for several classes of…

Combinatorics · Mathematics 2020-11-04 Štefko Miklavič , Primož Šparl

For a graph $G$ and $a,b\in V(G)$, the shortest path reconfiguration graph of $G$ with respect to $a$ and $b$ is denoted by $S(G,a,b)$. The vertex set of $S(G,a,b)$ is the set of all shortest paths between $a$ and $b$ in $G$. Two vertices…

Combinatorics · Mathematics 2017-05-29 John Asplund , Kossi Edoh , Ruth Haas , Yulia Hristova , Beth Novick , Brett Werner

A supergrid graph is a finite vertex-induced subgraph of the infinite graph whose vertex set consists of all points of the plane with integer coordinates and in which two vertices are adjacent if the difference of their x or y coordinates…

Computational Complexity · Computer Science 2019-08-21 Ruo-Wei Hung , Fatemeh Keshavarz-Kohjerdi

The Wiener index (the distance) of a connected graph is the sum of distances between all pairs of vertices. In this paper, we study the maximum possible value of this invariant among graphs on $n$ vertices with fixed number of blocks $p$.…

Discrete Mathematics · Computer Science 2019-05-08 Stéphane Bessy , François Dross , Katarína Hriňáková , Martin Knor , Riste Škrekovski

We introduce the cycle intersection graph of a graph, an adaptation of the cycle graph of a graph, and use the structure of these graphs to prove an upper bound for the decycling number of all even graphs. This bound is shown to be…

Combinatorics · Mathematics 2018-10-11 Michael Cary

The cycles are the only $2$-connected graphs in which any two nonadjacent vertices form a vertex cut. We generalize this fact by proving that for every integer $k\ge 3$ there exists a unique graph $G$ satisfying the following conditions:…

Combinatorics · Mathematics 2022-10-28 Yanan Hu , Xingzhi Zhan , Leilei Zhang

We give an overview of different approaches to measuring the similarity of, or the distance between, two graphs, highlighting connections between these approaches. We also discuss the complexity of computing the distances.

Discrete Mathematics · Computer Science 2025-03-19 Martin Grohe