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In descending generality I survey: five partial orderings of graphs, the induced-subgraph ordering, and examples like perfect, threshold, and mock threshold graphs. The emphasis is on how the induced subgraph ordering differs from other…

Combinatorics · Mathematics 2021-06-21 Thomas Zaslavsky

For a graph $G$, let $\nu_s(G)$ be the induced matching number of $G$. We prove that $\nu_s(G) \geq \frac{n(G)}{(\lceil\frac{\Delta}{2}\rceil+1) (\lfloor\frac{\Delta}{2}\rfloor+1)}$ for every graph of sufficiently large maximum degree…

Combinatorics · Mathematics 2014-06-11 Felix Joos

In this paper we show that prime sum graphs on $n$ vertices -- which are graphs on vertex set $\{1,2,...,n\}$ where $ij$ is an edge when $i+j$ is prime -- contain all trees with at most $\exp( c \log n / \log\log n)$ vertices as induced…

Number Theory · Mathematics 2023-06-08 Ernie Croot , Patrick Jin

We give a precise description of combed trees in terms of Kelly-Mac Lane graphs. We show that any combed tree is uniquely expressed as an allowable Kelly-Mac Lane graph of a certain shape. Conversely, we show that any such Kelly-Mac Lane…

Category Theory · Mathematics 2007-05-23 Eugenia Cheng

Let $G$ be a graph on $n$ vertices. A linear forest is a graph consisting of vertex-disjoint paths and isolated vertices. A maximum linear forest of $G$ is a subgraph of $G$ with maximum number of edges, which is a linear forest. We denote…

Combinatorics · Mathematics 2018-12-27 Xiuzhuan Duan , Jian Wang , Weihua Yang

An added edge to a graph is called an inset edge. Predicting k inset edges which minimize the average distance of a graph is known to be NP-Hard. However, when k = 1 the complexity of the problem is polynomial. In this paper, some tools for…

Computational Complexity · Computer Science 2020-08-14 M. H. Khalifeh , A. -H. Esfahanian

In this paper, we provide algorithms to rank, unrank, and randomly generate certain degree-restricted classes of Cayley trees. Specifically, we consider classes of trees that have a given degree sequence or a given multiset of degrees. If…

Combinatorics · Mathematics 2010-09-13 Jeffery B. Remmel , S. Gill Williamson

Limits of graphs were initiated recently in the two extreme contexts of dense and bounded degree graphs. This led to elegant limiting structures called graphons and graphings. These approach have been unified and generalized by authors in a…

Combinatorics · Mathematics 2013-12-03 Jaroslav Nesetril , Patrice Ossona De Mendez

An ordered graph is a graph with a linear ordering on its vertex set. We prove that for every positive integer $k$, there exists a constant $c_k>0$ such that any ordered graph $G$ on $n$ vertices with the property that neither $G$ nor its…

Combinatorics · Mathematics 2020-04-10 János Pach , István Tomon

We define a set $P$ to be a branching $k$-path vertex cover of an undirected forest $F$ if all leaves and isolated vertices (vertices of degree at most $1$) of $F$ belong to $P$ and every path on $k$ vertices (of length $k-1$) contains…

Combinatorics · Mathematics 2026-01-07 Mikhail Makarov

Paper proposes a model of large networks based on a random preferential attachment graph with addition of complete subgraphs (cliques). The proposed model refers to models of random graphs following the nonlinear preferential attachment…

Social and Information Networks · Computer Science 2019-04-05 E. B. Yudin

We introduce a novel stochastic growth process, the record-driven growth process, which originates from the analysis of a class of growing networks in a universal limiting regime. Nodes are added one by one to a network, each node…

Statistical Mechanics · Physics 2008-11-12 C. Godreche , J. M. Luck

We prove that a hereditary graph class $\mathcal{G}$ defined by finitely many excluded induced subgraphs has bounded tree-$\alpha$ if and only if it is "$(\mathrm{tw},\omega)$-bounded" (that is, for all $t\in \mathbb N$, the class of all…

Combinatorics · Mathematics 2026-05-05 Sepehr Hajebi , Sophie Spirkl

We continue the study of $(tw,\omega)$-bounded graph classes, that is, hereditary graph classes in which large treewidth is witnessed by the presence of a large clique, and the relation of this property to boundedness of the…

Combinatorics · Mathematics 2025-05-20 Claire Hilaire , Martin Milanič , Đorđe Vasić

In evolutionary biology, networks are becoming increasingly used to represent evolutionary histories for species that have undergone non-treelike or reticulate evolution. Such networks are essentially directed acyclic graphs with a leaf set…

Populations and Evolution · Quantitative Biology 2023-08-23 Katharina T. Huber , Leo van Iersel , Vincent Moulton , Guillaume Scholz

The status of a vertex $v$ in a connected graph is the sum of the distances from $v$ to all other vertices. The status sequence of a connected graph is the list of the statuses of all the vertices of the graph. In this paper we investigate…

Combinatorics · Mathematics 2020-02-03 Aida Abiad , Boris Brimkov , Alexander Grigoriev

We show that families of action graphs, with initial graphs which are linear of varying length, give rise to self-convolutions of the Catalan sequence. We prove this result via a comparison with planar rooted forests with a fixed number of…

Combinatorics · Mathematics 2021-07-28 Julia E. Bergner , Cedric Harper , Ryan Keller , Mathilde Rosi-Marshall

For $k\ge 1$, the $k$-independence number $\alpha_k$ of a graph is the maximum number of vertices that are mutually at distance greater than $k$. The well-known inertia and ratio bounds for the (1-)independence number $\alpha(=\alpha_1)$ of…

Combinatorics · Mathematics 2022-01-14 Aida Abiad , Cristina Dalfó , Miquel Àngel Fiol , Sjanne Zeijlemaker

We give here new upper bounds on the size of a smallest feedback vertex set in planar graphs with high girth. In particular, we prove that a planar graph with girth $g$ and size $m$ has a feedback vertex set of size at most $\frac{4m}{3g}$,…

Discrete Mathematics · Computer Science 2015-04-09 François Dross , Mickael Montassier , Alexandre Pinlou

Let $G$ be a simple finite connected graph. The line graph $L(G)$ of graph $G$ is the graph whose vertices are the edges of $G$, where $ef \in E(L(G))$ when $e \cap f \neq \emptyset$. Iteratively, the higher order line graphs are defined…

Combinatorics · Mathematics 2024-10-08 Aryan Sanghi , Devsi Bantva , Sudebkumar Prasant Pal
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