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Let $\{D_M\}_{M\geq 0}$ be the $n$-vertex random directed graph process, where $D_0$ is the empty directed graph on $n$ vertices, and subsequent directed graphs in the sequence are obtained by the addition of a new directed edge uniformly…

Combinatorics · Mathematics 2020-11-18 Richard Montgomery

We prove that every oriented tree on $n$ vertices with bounded maximum degree appears as a spanning subdigraph of every directed graph on $n$ vertices with minimum semidegree at least $n/2+o(n)$. This can be seen as a directed graph…

Combinatorics · Mathematics 2026-05-20 Richard Mycroft , Tássio Naia

We present a new algorithm for maintaining a DFS tree of an arbitrary directed graph under any sequence of edge insertions. Our algorithm requires a total of $O(m\cdot n)$ time in the worst case to process a sequence of edge insertions,…

Data Structures and Algorithms · Computer Science 2022-02-24 Giorgio Ausiello , Paolo G. Franciosa , Giuseppe F. Italiano , Andrea Ribichini

A perfect matching M in an edge-colored complete bipartite graph K_{n,n} is rainbow if no pair of edges in M have the same color. We obtain asymptotic enumeration results for the number of rainbow matchings in terms of the maximum number of…

Combinatorics · Mathematics 2011-04-15 Guillem Perarnau , Oriol Serra

A rainbow stacking of $r$-edge-colorings $\chi_1, \ldots, \chi_m$ of the complete graph on $n$ vertices is a way of superimposing $\chi_1, \ldots, \chi_m$ so that no edges of the same color are superimposed on each other. We determine a…

Combinatorics · Mathematics 2024-05-24 Noga Alon , Colin Defant , Noah Kravitz

Let's denote a complete $m$-ary rooted tree graph of height $n$ as $G$. In scope of this paper we prove the certain relations between the properties of $G$ and the expectation and variance of the distribution of lengths of strings,…

Combinatorics · Mathematics 2020-07-14 Yurii Lahodiuk

We investigate the existence of a rainbow Hamilton cycle in a uniformly edge-coloured randomly perturbed digraph. We show that for every $\delta \in (0,1)$ there exists $C = C(\delta) > 0$ such that the following holds. Let $D_0$ be an…

Combinatorics · Mathematics 2024-11-20 Kyriakos Katsamaktsis , Shoham Letzter , Amedeo Sgueglia

In the classical Erd\"os-R\'enyi random graph G(n,p) there are n vertices and each of the possible edges is independently present with probability p. The random graph G(n,p) is homogeneous in the sense that all vertices have the same…

Combinatorics · Mathematics 2016-02-10 Mihyun Kang , Angelica Pachón , Pablo M. Rodriguez

We determine the sharp threshold for the containment of all $n$-vertex trees of bounded degree in random geometric graphs with $n$ vertices. This provides a geometric counterpart of Montgomery's threshold result for binomial random graphs,…

Combinatorics · Mathematics 2025-05-23 Michael Anastos , Sahar Diskin , Dawid Ignasiak , Lyuben Lichev , Yetong Sha

We show that a randomly perturbed digraph, where we start with a dense digraph $D_\alpha$ and add a small number of random edges to it, will typically contain a fixed orientation of a bounded degree spanning tree. This answers a question…

Combinatorics · Mathematics 2024-08-21 Patryk Morawski , Kalina Petrova

A hypergraph $H$ is properly colored if for every vertex $v\in V(H)$, all the edges incident to $v$ have distinct colors. In this paper, we show that if $H_{1}$, \cdots, $H_{s}$ are properly-colored $k$-uniform hypergraphs on $n$ vertices,…

Combinatorics · Mathematics 2018-08-16 Hao Huang , Tong Li , Guanghui Wang

We study the rainbow version of the graph commonness property: a graph $H$ is $r$-rainbow common if the number of rainbow copies of $H$ (where all edges have distinct colors) in an $r$-coloring of edges of $K_n$ is maximized asymptotically…

Combinatorics · Mathematics 2024-07-11 Yihang Sun

A tree in an edge colored graph is said to be a rainbow tree if no two edges on the tree share the same color. Given two positive integers $k$, $\ell$ with $k\geq 3$, the \emph{$(k,\ell)$-rainbow index} $rx_{k,\ell}(G)$ of $G$ is the…

Combinatorics · Mathematics 2013-10-21 Qingqiong Cai , Xueliang Li , Jiangli Song

In a properly edge colored graph, a subgraph using every color at most once is called rainbow. In this thesis, we study rainbow cycles and paths in proper edge colorings of complete graphs, and we prove that in every proper edge coloring of…

Discrete Mathematics · Computer Science 2012-07-05 Heidi Gebauer , Frank Mousset

We prove that finding a rooted subtree with at least $k$ leaves in a digraph is a fixed parameter tractable problem. A similar result holds for finding rooted spanning trees with many leaves in digraphs from a wide family $\cal L$ that…

Data Structures and Algorithms · Computer Science 2007-05-23 Noga Alon , Fedor Fomin , Gregory Gutin , Michael Krivelevich , Saket Saurabh

An edge-colored graph $G$ is called rainbow if every edge of $G$ receives a different color. The anti-Ramsey number of $t$ edge-disjoint rainbow spanning trees, denoted by $r(n,t)$, is defined as the maximum number of colors in an…

Combinatorics · Mathematics 2019-11-19 Linyuan Lu , Zhiyu Wang

Let $G = (V, E)$ be an $n$-vertex edge-colored graph. In 2013, H. Li proved that if every vertex $v \in V$ is incident to at least $(n+1)/2$ distinctly colored edges, then $G$ admits a rainbow triangle. We establish a corresponding result…

Combinatorics · Mathematics 2019-12-05 Andrzej Czygrinow , Theodore Molla , Brendan Nagle , Roy Oursler

We prove that the treewidth of an Erd\"{o}s-R\'{e}nyi random graph $\rg{n, m}$ is, with high probability, greater than $\beta n$ for some constant $\beta > 0$ if the edge/vertex ratio $\frac{m}{n}$ is greater than 1.073. Our lower bound…

Discrete Mathematics · Computer Science 2009-08-03 Yong Gao

A subgraph of an edge-colored graph is called \emph{rainbow} if all of its edges have distinct colors. There has been much research on the topic of finding a large rainbow matching in a properly edge-colored graph, where a proper…

Combinatorics · Mathematics 2026-05-28 Debsoumya Chakraborti , Po-Shen Loh

We obtain new results for the probabilistic model introduced in Menshikov et al (2007) and Volkov (2006) which involves a $d$-ary regular tree. All vertices are coloured in one of $d$ distinct colours so that $d$ children of each vertex all…

Probability · Mathematics 2010-11-18 Skevi Michael , Stanislav Volkov