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We consider the number of common edges in two independent random spanning trees of a graph $G$. For complete graphs $K_n$, we give a new proof of the fact, originally obtained by Moon, that the distribution converges to a Poisson…

组合数学 · 数学 2025-06-09 Miklos Bona , Fabian Burghart , Stephan Wagner

We present a new characterization of $k$-trees based on their reduced clique graphs and $(k+1)$-line graphs, which are block graphs. We explore structural properties of these two classes, showing that the number of clique-trees of a…

组合数学 · 数学 2026-02-17 Lilian Markenzon , Allana S. S. Oliveira , Cybele T. M. Vinagre

Let $T$ be a tree with $t$ edges. We show that the number of isomorphic (labeled) copies of $T$ in a graph $G = (V,E)$ of minimum degree at least $t$ is at least \[2|E| \prod_{v \in V} (d(v) - t + 1)^{\frac{(t-1)d(v)}{2|E|}}.\]…

组合数学 · 数学 2015-11-24 Dhruv Mubayi , Jacques Verstraete

The Ascending Subgraph Decomposition (ASD) Conjecture asserts that every graph $G$ with ${n+1\choose 2}$ edges admits an edge decomposition $G=H_1\oplus\cdots \oplus H_n$ such that $H_i$ has $i$ edges and it is isomorphic to a subgraph of…

组合数学 · 数学 2015-12-08 Anna Lladó , Josep Maria Aroca

Tree-decompositions of graphs are of fundamental importance in structural and algorithmic graph theory. The main property of tree-decompositions is the width (the maximum size of a bag minus 1). We show that every graph has a…

组合数学 · 数学 2026-05-08 David R. Wood

In Part I of this series we described three algorithms that construct canonical tree-decompositions of graphs which distinguish all their k-blocks and tangles of order k. We now establish bounds on the number of parts in these…

组合数学 · 数学 2014-04-25 Johannes Carmesin , Reinhard Diestel , Matthias Hamann , Fabian Hundertmark

The degree sequence of a graph is a numerical method to characterize the properties of graphs. Generalized forms of degree sequences exist for complete graphs and complete graphs. Nikolopolus et al. characterized the number of spanning…

组合数学 · 数学 2019-06-17 Joshua Steier

We prove that there is $c>0$ such that for all sufficiently large $n$, if $T_1,\dots,T_n$ are any trees such that $T_i$ has $i$ vertices and maximum degree at most $cn/\log n$, then $\{T_1,\dots,T_n\}$ packs into $K_n$. Our main result…

组合数学 · 数学 2022-06-22 Peter Allen , Julia Böttcher , Dennis Clemens , Jan Hladký , Diana Piguet , Anusch Taraz

Let $\mathcal G$ be a separable family of graphs. Then for all positive constants $\epsilon$ and $\Delta$ and for every sufficiently large integer $n$, every sequence $G_1,\dotsc,G_t\in\mathcal G$ of graphs of order $n$ and maximum degree…

组合数学 · 数学 2016-06-01 Asaf Ferber , Choongbum Lee , Frank Mousset

Let $k\geq\ell\geq1$ and $n\geq 1$ be integers. Let $G(k,n)$ be the complete $k$-partite graph with $n$ vertices in each colour class. An $\ell$-decomposition of $G(k,n)$ is a set $X$ of copies of $K_k$ in $G(k,n)$ such that each copy of…

组合数学 · 数学 2012-02-20 Ruy Fabila-Monroy , David R. Wood

A subgraph of an edge-coloured graph is called rainbow if all its edges have distinct colours. The study of rainbow subgraphs goes back more than two hundred years to the work of Euler on Latin squares. Since then rainbow structures have…

组合数学 · 数学 2018-12-11 Richard Montgomery , Alexey Pokrovskiy , Benny Sudakov

We characterize all partitions of the complete twisted graph $T_{2n}$ into plane spanning trees. In the case of partitions of $T_{2n}$ into isomorphic plane spanning trees, we show that all trees in these partitions must be balanced double…

组合数学 · 数学 2025-10-31 Ana Paulina Figueroa , Eduardo Rivera-Campo

Symbolic ultrametrics define edge-colored complete graphs K_n and yield a simple tree representation of K_n. We discuss, under which conditions this idea can be generalized to find a symbolic ultrametric that, in addition, distinguishes…

离散数学 · 计算机科学 2015-01-27 Marc Hellmuth , Nicolas Wieseke

We consider the class F of 2-connected non-planar K_{3,3}-subdivision-free graphs that are embeddable in the projective plane. We show that these graphs admit a unique decomposition as a graph K_5 (the core) where the edges are replaced by…

组合数学 · 数学 2010-12-23 Andrei Gagarin , Gilbert Labelle , Pierre Leroux

Let G be a graph in a 3-manifold M. We compress the pair (M,G) along admissible 2-spheres as long as possible. What we get is a root of (M,G). Our main result is that for any pair (M,G) the root exists and is unique. As a corollary we get…

几何拓扑 · 数学 2007-05-23 Sergei Matveev

In this short note, we study pairwise edge-disjoint rainbow spanning trees in properly edge-coloured complete graphs, where a graph is rainbow if its edges have distinct colours. Brualdi and Hollingsworth conjectured that every $K_n$…

组合数学 · 数学 2017-04-25 József Balogh , Hong Liu , Richard Montgomery

A spanning tree of a graph $G$ is a connected acyclic spanning subgraph of $G$. We consider enumeration of spanning trees when $G$ is a $2$-tree, meaning that $G$ is obtained from one edge by iteratively adding a vertex whose neighborhood…

离散数学 · 计算机科学 2016-07-21 P. Renjith , N. Sadagopan , Douglas B. West

Motivated by the question of how macromolecules assemble, the notion of an {\it assembly tree} of a graph is introduced. Given a graph $G$, the paper is concerned with enumerating the number of assembly trees of $G$, a problem that applies…

组合数学 · 数学 2012-04-18 Andrew Vince , Miklos Bona

The 3-decomposition conjecture is wide open. It asserts that every finite connected cubic graph can be decomposed into a spanning tree, a disjoint union of cycles, and a matching. We show that every such decomposition is derived from a…

组合数学 · 数学 2022-02-22 Oliver Bachtler , Irene Heinrich

Let $K_m-H$ be the graph obtained from $K_m$ by removing the edges set $E(H)$ of $H$ where $H$ is a subgraph of $K_m$. In this paper, we characterize the potentially $K_5-P_4$ and $K_5-Y_4$-graphic sequences where $Y_4$ is a tree on 5…

组合数学 · 数学 2009-11-15 Lili Hu , Chunhui Lai , Ping Wang