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Motivated by an induced counterpart of treewidth sparsifiers (i.e., sparse subgraphs keeping the treewidth large) provided by the celebrated Grid Minor theorem of Robertson and Seymour [JCTB '86] or by a classic result of Chekuri and…

Combinatorics · Mathematics 2024-05-24 Édouard Bonnet

For graphs $F$ and $H$, let $i(F)$ denote the inducibility of $F$ and let $i_H(F)$ denote the inducibility of $F$ over $H$-free graphs. We prove that for almost all graphs $F$ on a given number of vertices, $i_{K_k}(F)$ attains infinitely…

Combinatorics · Mathematics 2025-12-19 Raphael Yuster

We prove that for all $0\leq t\leq k$ and $d\geq 2k$, every graph $G$ with treewidth at most $k$ has a `large' induced subgraph $H$, where $H$ has treewidth at most $t$ and every vertex in $H$ has degree at most $d$ in $G$. The order of $H$…

Combinatorics · Mathematics 2007-05-23 Prosenjit Bose , Vida Dujmovic , David R. Wood

In the first paper of the Graph Minors series [JCTB '83], Robertson and Seymour proved the Forest Minor theorem: the $H$-minor-free graphs have bounded pathwidth if and only if $H$ is a forest. In recent years, considerable effort has been…

Combinatorics · Mathematics 2025-12-02 Édouard Bonnet , Benjamin Duhamel , Robert Hickingbotham

We consider the following problem: Let $H$ and $F$ be two graphs on $k$ vertices and assume $F \neq H$. We say that $H$ and $F$ are incomparable if neither $F$ nor $H$ contains the other. Let $H$ be a graph on $k$ vertices and let $G$ be a…

Combinatorics · Mathematics 2026-05-28 Yair Caro , Zsolt Tuza , Christina Zarb

Let $F(G)$ be the number of forests of a graph $G$. Similarly let $C(G)$ be the number of connected spanning subgraphs of a connected graph $G$. We bound $F(G)$ and $C(G)$ for regular graphs and for graphs with fixed average degree. Among…

Combinatorics · Mathematics 2021-08-03 Márton Borbényi , Péter Csikvári , Haoran Luo

We say a class $\mathcal{C}$ of graphs is clean if for every positive integer $t$ there exists a positive integer $w(t)$ such that every graph in $\mathcal{C}$ with treewidth more than $w(t)$ contains an induced subgraph isomorphic to one…

Combinatorics · Mathematics 2023-11-08 Tara Abrishami , Bogdan Alecu , Maria Chudnovsky , Sepehr Hajebi , Sophie Spirkl

For a tree decomposition $\mathcal{T}$ of a graph $G$, by $\mu(\mathcal{T})$ we denote the size of a largest induced matching in $G$ all of whose edges intersect one bag of $\mathcal{T}$. Induced matching treewidth of a graph $G$ is the…

Data Structures and Algorithms · Computer Science 2024-02-27 Paloma T. Lima , Martin Milanič , Peter Muršič , Karolina Okrasa , Paweł Rzążewski , Kenny Štorgel

A spanning subgraph $F$ of a graph $G$ is called perfect if $F$ is a forest, the degree $d_F(x)$ of each vertex $x$ in $F$ is odd, and each tree of $F$ is an induced subgraph of $G$. We provide a short proof of the following theorem of A.D.…

Discrete Mathematics · Computer Science 2015-01-07 Gregory Gutin

We define the induced arboricity of a graph $G$, denoted by ${\rm ia}(G)$, as the smallest $k$ such that the edges of $G$ can be covered with $k$ induced forests in $G$. This notion generalizes the classical notions of the arboricity and…

Combinatorics · Mathematics 2018-03-07 Maria Axenovich , Philip Dörr , Jonathan Rollin , Torsten Ueckerdt

Let $G$ be a graph and let $f$ be a positive integer-valued function on $V(G)$. In this paper, we show that if for all $S\subseteq V(G)$, $\omega(G\setminus S)<\sum_{v\in S}(f(v)-2)+2+\omega(G[S])$, then $G$ has a spanning tree $T$…

Combinatorics · Mathematics 2022-05-10 Morteza Hasanvand

Let $\mathcal{C}$ and $\mathcal{D}$ be hereditary graph classes. Consider the following problem: given a graph $G\in\mathcal{D}$, find a largest, in terms of the number of vertices, induced subgraph of $G$ that belongs to $\mathcal{C}$. We…

Computational Complexity · Computer Science 2019-10-03 Jana Novotná , Karolina Okrasa , Michał Pilipczuk , Paweł Rzążewski , Erik Jan van Leeuwen , Bartosz Walczak

We prove the rather counterintuitive result that there exist finite transitive graphs H and integers k such that the Free Uniform Spanning Forest in the direct product of the k-regular tree and H has infinitely many trees almost surely.…

Probability · Mathematics 2021-01-26 Gábor Pete , Ádám Timár

A spanning tree $T$ of a connected graph $G$ is a subgraph of $G$ that is a tree covers all vertices of $G$. The leaf distance of $T$ is defined as the minimum of distances between any two leaves of $T$. A fractional matching of a graph $G$…

Combinatorics · Mathematics 2025-07-16 Sizhong Zhou

We prove that the uniform spanning forests of $\mathbb{Z}^d$ and $\mathbb{Z}^{\ell}$ have qualitatively different connectivity properties whenever $\ell >d \geq 4$. In particular, we consider the graph formed by contracting each tree of the…

Probability · Mathematics 2018-10-16 Tom Hutchcroft , Yuval Peres

We prove that in both the free and the wired uniform spanning forest (FUSF and WUSF) of any unimodular random rooted network (in particular, of any Cayley graph), it is impossible to distinguish the connected components of the forest from…

Probability · Mathematics 2018-05-01 Tom Hutchcroft , Asaf Nachmias

In this article we investigate the Uniform Spanning Forest ($\mathsf{USF}$) in the nearest-neighbour integer lattice $\mathbf{Z}^{d+1} = \mathbf{Z}\times \mathbf{Z}^d$ with an assignment of conductances that makes the underlying (Network)…

Probability · Mathematics 2020-09-03 Guillermo Martinez Dibene

Considering the wired uniform spanning forest on a nonunimodular transitive graph, we show that almost surely each tree of the wired uniform spanning forest is light. More generally we study the tilted volumes for the trees in the wired…

Probability · Mathematics 2020-12-04 Pengfei Tang

It is known that every graph of sufficiently large chromatic number and bounded clique number contains, as an induced subgraph, a subdivision of any fixed forest, and a subdivision of any fixed cycle. Equivalently, forests and triangles are…

Combinatorics · Mathematics 2021-05-24 Maria Chudnovsky , Alex Scott , Paul Seymour

Let $G$ be a graph and $a(G)$, LIF$(G)$ denote the maximum orders of an induced forest and an induced linear forest of $G$, respectively. It is well-known that if $G$ is an $r$-regular graph of order $n$, then $a(G) \geq \frac{2}{r+1}n$. In…

Combinatorics · Mathematics 2019-11-07 Saieed Akbari , Alireza Amanihamedani , Sepehr Mousavi , Hesam Nikpey , Soheil Sheybani