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The pseudoforest version of the Strong Nine Dragon Tree Conjecture states that if a graph $G$ has maximum average degree $\text{mad}(G) = 2 \max_{H \subseteq G} \frac{e(G)}{v(G)}$ at most $2(k + \frac{d}{k+d+1})$, then it has a…

Combinatorics · Mathematics 2025-06-23 Sebastian Mies , Benjamin Moore , Evelyne Smith-Roberge

In 2006, Bar\'at and Thomassen posed the following conjecture: for each tree $T$, there exists a natural number $k_T$ such that, if $G$ is a $k_T$-edge-connected graph and $|E(G)|$ is divisible by $|E(T)|$, then $G$ admits a decomposition…

Combinatorics · Mathematics 2015-09-23 Fabio Botler , Guilherme O. Mota , Marcio T. I. Oshiro , Yoshiko Wakabayashi

We study $k$-star decompositions, that is, partitions of the edge set into disjoint stars with $k$ edges, in the uniformly random $d$-regular graph model $\mathcal{G}_{n,d}$. Using the small subgraph conditioning method, we prove an…

Combinatorics · Mathematics 2026-02-17 Michelle Delcourt , Catherine Greenhill , Mikhail Isaev , Bernard Lidický , Luke Postle

We show a general result known as the Erdos_Sos Conjecture: if $E(G)>{1/2}(k-1)n$ where $G$ has order $n$ then $G$ contains every tree of order $k+1$ as a subgraph.

Discrete Mathematics · Computer Science 2010-08-02 Jesse Gilbert

An old conjecture of Ringel states that every tree with $m$ edges decomposes the complete graph $K_{2m+1}$. The best known lower bound for the order of a complete graph which admits a decomposition by every given tree with $m$ edges is…

Combinatorics · Mathematics 2015-12-08 Anna Lladó

A path (resp. cycle) decomposition of a graph $G$ is a set of edge-disjoint paths (resp. cycles) of $G$ that covers the edge set of $G$. Gallai (1966) conjectured that every graph on $n$ vertices admits a path decomposition of size at most…

Combinatorics · Mathematics 2017-06-15 Fábio Botler , Maycon Sambinelli , Rafael S. Coelho , Orlando Lee

A variant of the Erd\H{o}s-S\'os conjecture, posed by Havet, Reed, Stein and Wood, states that every graph with minimum degree at least $\lfloor 2k/3 \rfloor$ and maximum degree at least $k$ contains a copy of every tree with $k$ edges.…

Combinatorics · Mathematics 2025-12-19 Alexey Pokrovskiy , Leo Versteegen , Ella Williams

A graph is called pseudo-outerplanar if each block has an embedding on the plane in such a way that the vertices lie on a fixed circle and the edges lie inside the disk of this circle with each of them crossing at most one another. In this…

Combinatorics · Mathematics 2011-10-20 Xin Zhang , Guizhen Liu , Jian-Liang Wu

A famous conjecture of Erd\H{o}s and S\'os states that every graph with average degree more than $k - 1$ contains all trees with $k$ edges as subgraphs. We prove that the Erd\H{o}s-S\'os conjecture holds approximately, if the size of the…

Combinatorics · Mathematics 2018-10-30 Václav Rozhoň

A $k$-star decomposition of a graph is a partition of its edges into $k$-stars (i.e., $k$ edges with a common vertex). The paper studies the following problem: for what values of $k>d/2$ does the random $d$-regular graph have a $k$-star…

Combinatorics · Mathematics 2025-03-24 Viktor Harangi

A typical decomposition question asks whether the edges of some graph $G$ can be partitioned into disjoint copies of another graph $H$. One of the oldest and best known conjectures in this area, posed by Ringel in 1963, concerns the…

Combinatorics · Mathematics 2020-02-25 Richard Montgomery , Alexey Pokrovskiy , Benny Sudakov

An (edge) decomposition of a graph $G$ is a set of subgraphs of $G$ whose edge sets partition the edge set of $G$. Here we show, for each odd $\ell \geq 5$, that any graph $G$ of sufficiently large order $n$ with minimum degree at least…

Combinatorics · Mathematics 2024-11-27 Darryn Bryant , Peter Dukes , Daniel Horsley , Barbara Maenhaut , Richard Montgomery

The fractional arboricity of a digraph $D$, denoted by $\gamma(D)$, is defined as $\gamma(D)= \max_{H \subseteq D, |V(H)| >1} \frac {|A(H)|} {|V(H)|-1}$. Frank in [Covering branching, Acta Scientiarum Mathematicarum (Szeged) 41 (1979),…

Combinatorics · Mathematics 2022-05-06 Hui Gao , Daqing Yang

We proved that for every sufficiently large $n$, the complete graph $K_{2n}$ with an arbitrary edge signing $\sigma: E(K_{2n}) \to \{-1, +1\}$ admits a high discrepancy $1$-factor decomposition. That is, there exists a universal constant $c…

Combinatorics · Mathematics 2025-03-24 Jiangdong Ai , Fankang He , Seonghyuk Im , Hyunwoo Lee

We consider the problem of decomposing the edges of a directed graph into as few paths as possible. There is a natural lower bound for the number of paths needed in an edge decomposition of a directed graph $D$ in terms of its degree…

Combinatorics · Mathematics 2021-09-29 Alberto Espuny Díaz , Viresh Patel , Fabian Stroh

We prove that for every complete multipartite graph $F$ there exist very dense graphs $G_n$ on $n$ vertices, namely with as many as ${n\choose 2}-cn$ edges for all $n$, for some constant $c=c(F)$, such that $G_n$ can be decomposed into…

Combinatorics · Mathematics 2015-01-16 Csilla Bujtás , Zsolt Tuza

A graph $G$ contains another graph $H$ as an immersion if $H$ can be obtained from a subgraph of $G$ by splitting off edges and removing isolated vertices. There is an obvious necessary degree condition for the immersion containment: if $G$…

Combinatorics · Mathematics 2022-09-27 Chun-Hung Liu

A $T$-decomposition of a graph $G$ is a set of edge-disjoint copies of $T$ in $G$ that cover the edge set of $G$. Graham and H\"aggkvist (1989) conjectured that any $2\ell$-regular graph $G$ admits a $T$-decomposition if $T$ is a tree with…

Combinatorics · Mathematics 2016-07-07 Fábio Botler , Alexandre Talon

Let $k$, $\lambda$ and $\mu$ be positive integers. A decomposition of a multigraph $ \lambda G$ into edge-disjoint subgraphs $G_1, \ldots , G_k$ is said to be \emph{enclosed} by a decomposition of a multigraph $\mu H$ into edge-disjoint…

Combinatorics · Mathematics 2016-08-26 Carl Feghali , Matthew Johnson

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…

Combinatorics · Mathematics 2020-08-13 J. Bang-Jensen , F. Havet , M. Kriesell , A. Yeo