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We consider large uniform labeled random graphs in different classes with prescribed decorations in their modular decomposition. Our main result is the estimation of the number of copies of every graph as an induced subgraph. As a…

组合数学 · 数学 2023-10-25 Théo Lenoir

A point visibility graph is a graph induced by a set of points in the plane where the vertices of the graph represent the points in the point set and two vertices are adjacent if and only if no other point from the point set lies on the…

离散数学 · 计算机科学 2018-05-17 Anne-Sophie Himmel , Clemens Hoffmann , Pascal Kunz , Vincent Froese , Manuel Sorge

An almost self-centered graph is a connected graph of order $n$ with exactly $n-2$ central vertices, and an almost peripheral graph is a connected graph of order $n$ with exactly $n-1$ peripheral vertices. We determine (1) the maximum girth…

组合数学 · 数学 2021-06-24 Yanan Hu , Xingzhi Zhan

In this paper we establish all extremal graphs with respect to augmented eccentric connectivity index among all (simple connected) graphs, among trees and among trees with perfect matching. For graphs that turn out to be extremal explicit…

组合数学 · 数学 2013-06-19 Jelena Sedlar

Let $G$ be a large (simple, unlabeled) dense graph on $n$ vertices. Suppose that we only know, or can estimate, the empirical distribution of the number of subgraphs $F$ that each vertex in $G$ participates in, for some fixed small graph…

信息论 · 计算机科学 2023-08-08 Shahar Stein Ioushua , Ofer Shayevitz

We introduce new sufficient conditions for intrinsic knotting and linking. A graph on n vertices with at least 4n-9 edges is intrinsically linked. A graph on n vertices with at least 5n-14 edges is intrinsically knotted. We also classify…

几何拓扑 · 数学 2007-05-23 J. Campbell , T. W. Mattman , R. Ottman , J. Pyzer , M. Rodrigues , S. Williams

Given graphs H_1,...,H_k, we study the minimum order of a graph G such that for each i, the induced copies of H_i in G cover V(G). We prove a general upper bound of twice the sum of the numbers m_i, where m_i is one less than the order of…

组合数学 · 数学 2007-05-23 Zoltan Furedi , Dhruv Mubayi , Douglas B. West

We show that if a graph contains few induced copies of a given graph then its edges are distribited unevenly.

组合数学 · 数学 2007-05-23 Vladimir Nikiforov

We give upper and lower bounds on the number of graphs of fixed degree which have a positive density of triangles. In particular, we show that there are very few such graphs, when compared to the number of graphs without this restriction.…

数学物理 · 物理学 2015-06-26 Pierre Collet , Jean-Pierre Eckmann

Extending the work of Godsil and others, we investigate the notion of the inverse of a graph (specifically, of bipartite graphs with a unique perfect matching). We provide a concise necessary and sufficient condition for the invertibility…

组合数学 · 数学 2011-08-19 Cam McLeman , Erin McNicholas

The spectral density of random graphs with topological constraints is analysed using the replica method. We consider graph ensembles featuring generalised degree-degree correlations, as well as those with a community structure. In each case…

无序系统与神经网络 · 物理学 2011-04-08 Tim Rogers , Conrad Pérez Vicente , Koujin Takeda , Isaac Pérez Castillo

We prove two estimates for the expectation of the exponential of a complex function of a random permutation or subset. Using this theory, we find asymptotic expressions for the expected number of copies and induced copies of a given graph…

组合数学 · 数学 2021-07-01 Catherine Greenhill , Mikhail Isaev , Brendan D. McKay

The number of embeddings of minimally rigid graphs in $\mathbb{R}^D$ is (by definition) finite, modulo rigid transformations, for every generic choice of edge lengths. Even though various approaches have been proposed to compute it, the gap…

代数几何 · 数学 2020-01-24 Evangelos Bartzos , Ioannis Emiris , Jan Legerský , Elias Tsigaridas

We determine the maximum number of maximal independent sets of arbitrary graphs in terms of their covering numbers and we completely characterize the extremal graphs. As an application, we give a similar result for K\"onig-Egerv\'ary graphs…

组合数学 · 数学 2016-10-20 Do Trong Hoang , Tran Nam Trung

An oriented graph $\overrightarrow{G}$ is pushably $k$-critical if it is not pushably $k$-colorable, but every proper subgraph of $\overrightarrow{G}$ is. The main result of this article is that every pushably $3$-critical oriented graph on…

离散数学 · 计算机科学 2025-09-15 Tapas Das , Pavan P D , Sagnik Sen , S Taruni

We describe some metric properties of incomparability graphs. We consider the problem of the existence of infinite paths, either induced or isometric, in the incomparability graph of a poset. Among other things, we show that if the…

组合数学 · 数学 2022-02-22 Maurice Pouzet , Imed Zaguia

We prove properties of extremal graphs of girth 5 and order 20 <=v <= 32. In each case we identify the possible minimum and maximum degrees, and in some cases prove the existence of (non-trivial) embedded stars. These proofs allow for…

组合数学 · 数学 2017-08-24 Alice Miller , Michael Codish

In this paper we give tight upper bounds on the total domination number, the weakly connected domination number and the connected domination number of a graph in terms of order and Euler characteristic. We also present upper bounds for the…

组合数学 · 数学 2013-10-08 Vladimir Samodivkin

We aim to find orientations of mixed graphs optimizing the total reachability, a problem that has applications in causality and biology. For given a digraph $D$, we use $P(D)$ for the set of ordered pairs of distinct vertices in $V(D)$ and…

计算复杂性 · 计算机科学 2025-09-24 Florian Hörsch

This paper considers *-graphs in which all vertices have degree 4 or 6, and studies the question of calculating the genus of orientable 2-surfaces into which such graphs may be embedded. A *-graph is a graph endowed with a formal adjacency…

组合数学 · 数学 2012-12-27 Tyler Friesen , Vassily Manturov