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Given an edge-weighted tree $T$ with $n$ leaves, sample the leaves uniformly at random without replacement and let $W_k$, $2 \le k \le n$, be the length of the subtree spanned by the first $k$ leaves. We consider the question, "Can $T$ be…

组合数学 · 数学 2015-06-04 Steven N. Evans , Daniel Lanoue

Completely independent spanning trees in a graph $G$ are spanning trees of $G$ such that for any two distinct vertices of $G$, the paths between them in the spanning trees are pairwise edge-disjoint and internally vertex-disjoint. In this…

组合数学 · 数学 2022-09-21 Toru Hasunuma

The problem of packing as many subgraphs isomorphic to $H \in \mathcal H$ as possible in a graph for a class $\mathcal H$ of graphs is well studied in the literature. Both vertex-disjoint and edge-disjoint versions are known to be…

数据结构与算法 · 计算机科学 2023-12-15 Tatsuya Gima , Tesshu Hanaka , Yasuaki Kobayashi , Yota Otachi , Tomohito Shirai , Akira Suzuki , Yuma Tamura , Xiao Zhou

A subgraph in an edge-colored graph is multicolored if all its edges receive distinct colors. In this paper, we study the proper edge-colorings of the complete bipartite graph $K_{m,n}$ which forbid multicolored cycles. Mainly, we prove…

组合数学 · 数学 2014-07-02 Hung-Lin Fu , Yuan-Hsun Lo , Ryo-Yu Pei

A $P_\ell$-decomposition of a graph $G$ is a set of paths with $\ell$ edges in $G$ that cover the edge set of $G$. Favaron, Genest, and Kouider (2010) conjectured that every $(2k+1)$-regular graph that contains a perfect matching admits a…

组合数学 · 数学 2020-12-10 Fábio Botler , Luiz Hoffmann

A classical result of Koml\'os, S\'ark\"ozy and Szemer\'edi shows that every large $n$-vertex graph with minimum degree at least $(1/2+\gamma)n$ contains all spanning trees of bounded degree. We generalised this result to loose spanning…

组合数学 · 数学 2025-02-10 Yaobin Chen , Allan Lo

Generalizing well-known results of Erd\H{o}s and Lov\'asz, we show that every graph $G$ contains a spanning $k$-partite subgraph $H$ with $\lambda{}(H)\geq \lceil{}\frac{k-1}{k}\lambda{}(G)\rceil$, where $\lambda{}(G)$ is the…

组合数学 · 数学 2020-08-13 J. Bang-Jensen , F. Havet , M. Kriesell , A. Yeo

Haj\'os conjecture asserts that a simple Eulerian graph on n vertices can be decomposed into at most (n - 1)/2 cycles. The conjecture is only proved for graph classes in which every element contains vertices of degree 2 or 4. We develop new…

组合数学 · 数学 2017-08-11 Elke Fuchs , Laura Gellert , Irene Heinrich

We prove that all knots with unknotting number at most 21 are smoothly slice in the K3 surface. We also prove a more general statement for 4-manifolds that contain a plumbing tree of spheres. Our strategy is based on a flexible method to…

几何拓扑 · 数学 2025-08-18 Marco Marengon , Stefan Mihajlović

In 1986, Janson showed that the number of edges in the union of $k$ random spanning trees in the complete graph $K_n$ is a shifted Poisson distribution. Using results from the theory of electrical networks, we provide a new proof of this…

组合数学 · 数学 2020-02-17 Austen James , Matthew Larson , Daniel Montealegre , Andrew Salmon

Let $G=(V,E)$ be a complete $n$-vertex graph with distinct positive edge weights. We prove that for $k\in\{1,2,...,n-1\}$, the set consisting of the edges of all minimum spanning trees (MSTs) over induced subgraphs of $G$ with $n-k+1$…

组合数学 · 数学 2007-05-23 Gregory B. Sorkin , Angelika Steger , Rico Zenklusen

We consider the existence problem of uniformly resolvable decompositions of $K_v$ into subgraphs such that each resolution class contains only blocks isomorphic to the same graph. We give a complete solution for the case in which one…

组合数学 · 数学 2023-12-18 Jehyun Lee , Melissa Keranen

Let $\mathcal{G}$ be the set of simple graphs (or multigraphs) $G$ such that for each $G \in \mathcal{G}$ there exists at least two non-empty disjoint proper subsets $V_{1},V_{2}\subseteq V(G)$ satisfying $V(G)\setminus(V_{1} \cup…

组合数学 · 数学 2018-11-19 Cunxiang Duan , Ligong Wang , Xiangxiang Liu

For a non-negative integer $k$, a vertex cut in a graph is $k$-degenerate if it induces a $k$-degenerate subgraph. We show that a graph of order $n$ at least $2k+2$ without a $k$-degenerate cut has the size at least…

组合数学 · 数学 2026-01-06 Thilo Hartel , Johannes Rauch , Dieter Rautenbach

We prove that the number of edges of a multigraph $G$ with $n$ vertices is at most $O(n^2\log n)$, provided that any two edges cross at most once, parallel edges are noncrossing, and the lens enclosed by every pair of parallel edges in $G$…

组合数学 · 数学 2022-02-24 Jacob Fox , Janos Pach , Andrew Suk

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…

数据结构与算法 · 计算机科学 2007-05-23 Noga Alon , Fedor Fomin , Gregory Gutin , Michael Krivelevich , Saket Saurabh

We provide a structural description of, and invariants for, maximum spanning tree-packable graphs, i.e. those graphs G for which the edge connectivity of G is equal to the maximum number of edge-disjoint spanning trees in G. These graphs…

组合数学 · 数学 2012-03-07 Robert F. Bailey , Brett Stevens

A classical result by Otter shows that the complete graph has an exponential number of non-isomorphic spanning trees. This was recently extended by Lee to every almost regular graph of sufficiently large degree. In this paper, we consider…

组合数学 · 数学 2026-03-19 Veronica Bitonti , Lukas Michel , Alex Scott

Let $k\geq2$ be an integer. A $k$-tree is a tree with maximum degree at most $k$. In this paper, we give a closure result on spanning $k$-trees of graphs with given minimum degree. Let $\delta\geq1$ be an integer, and $G$ be a connected…

组合数学 · 数学 2026-04-28 Wenqian Zhang

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 and has been the focus of extensive…

组合数学 · 数学 2019-04-24 Richard Montgomery , Alexey Pokrovskiy , Benny Sudakov