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Shrub-depth and rank-depth are dense analogues of the tree-depth of a graph. It is well known that a graph has large tree-depth if and only if it has a long path as a subgraph. We prove an analogous statement for shrub-depth and rank-depth,…

Combinatorics · Mathematics 2022-10-05 O-joung Kwon , Rose McCarty , Sang-il Oum , Paul Wollan

We introduce the tree-decomposition-based graph parameter Odd-Cycle-Packing-treewidth (OCP-tw) as a width parameter that asks to decompose a given graph into pieces of bounded odd cycle packing number. The parameter OCP-tw is monotone under…

Combinatorics · Mathematics 2025-11-14 Mujin Choi , Maximilian Gorsky , Gunwoo Kim , Caleb McFarland , Sebastian Wiederrecht

We prove that, for every $k=1,2,...,$ every shortest-path metric on a graph of pathwidth $k$ embeds into a distribution over random trees with distortion at most $c$ for some $c=c(k)$. A well-known conjecture of Gupta, Newman, Rabinovich,…

Metric Geometry · Mathematics 2012-10-09 James R. Lee , Anastasios Sidiropoulos

Albertson and Berman conjectured that every planar graph has an induced forest on half of its vertices. The best known lower bound, due to Borodin, is that every planar graph has an induced forest on two fifths of its vertices. In a related…

Combinatorics · Mathematics 2026-03-19 Glencora Borradaile , Hung Le , Melissa Sherman-Bennett

We prove that any \(2\)-connected graph \(G\) on \(n\) vertices with minimum degree \(\delta(G) \ge \frac{n}{4}+2\) contains a \(2\)-connected subgraph of order \(k\) for every integer \(k\) with \(4 \le k \le n\). This improves a previous…

Combinatorics · Mathematics 2026-03-13 Haiyang Liu , Bo Ning

We prove an asymptotically tight bound on the extremal density guaranteeing subdivisions of bounded-degree bipartite graphs with a mild separability condition. As corollaries, we answer several questions of Reed and Wood on embedding sparse…

Combinatorics · Mathematics 2023-03-22 John Haslegrave , Jaehoon Kim , Hong Liu

The treewidth of a graph is an important invariant in structural and algorithmic graph theory. This paper studies the treewidth of line graphs. We show that determining the treewidth of the line graph of a graph $G$ is equivalent to…

Combinatorics · Mathematics 2014-09-25 Daniel J. Harvey , David R. Wood

Given an edge-weighted graph $G=(V,E)$ and a set $E_0\subset E$, the incremental network design problem with minimum spanning trees asks for a sequence of edges $e'_1,\ldots,e'_T\in E\setminus E_0$ minimizing $\sum_{t=1}^Tw(X_t)$ where…

Combinatorics · Mathematics 2017-02-09 Konrad Engel , Thomas Kalinowski , Martin W. P. Savelsbergh

We show that there exists a graph $G$ with $O(n)$ nodes, where any forest of $n$ nodes is a node-induced subgraph of $G$. Furthermore, for constant arboricity $k$, the result implies the existence of a graph with $O(n^k)$ nodes that…

Data Structures and Algorithms · Computer Science 2016-02-17 Stephen Alstrup , Søren Dahlgaard , Mathias Bæk Tejs Knudsen

In this paper, we prove that there exists an absolute constant $g_0$ such that, for every integer $k\ge 3$, every graph $G$ with $\delta(G)\ge k$ and $g(G)\ge g_0$ contains an induced subdivision of $K_{k+1}$. This answers, in a strong…

Combinatorics · Mathematics 2026-05-19 Peiru Kuang , Yan Wang

The graph parameter treedepth is minor-monotone; hence, the class of graphs with treedepth at most $k$ is minor-closed. By the Graph Minor Theorem, such a class is characterized by a finite set of forbidden minors. A conjecture of…

Discrete Mathematics · Computer Science 2025-12-02 Kolja Kühn

For a real c \geq 1 and an integer n, let f(n,c) denote the maximum integer f so that every graph on n vertices contains an induced subgraph on at least f vertices in which the maximum degree is at most c times the minimum degree. Thus, in…

Combinatorics · Mathematics 2008-02-25 Noga Alon , Michael Krivelevich , Benny Sudakov

We say that a graph $F$ can be embedded into a graph $G$ if $G$ contains an isomorphic copy of $F$ as a subgraph. Guo and Volkmann \cite{GV} conjectured that if $G$ is a connected graph with at least $n$ vertices and minimum degree at least…

Combinatorics · Mathematics 2022-01-03 Zilong Yan , Yuejian Peng

We apply a recent duality theorem for tangles in abstract separation systems to derive tangle-type duality theorems for width-parameters in graphs and matroids. We further derive a duality theorem for the existence of clusters in large data…

Combinatorics · Mathematics 2020-01-24 Reinhard Diestel , Sang-il Oum

In this paper, we consider a structural and geometric property of graphs, namely the presence of large expanders. The problem of finding such structures was first considered by Krivelevich [SIAM J. Disc. Math. 32 1 (2018)]. Here, we show…

Combinatorics · Mathematics 2023-02-22 Baptiste Louf , Fiona Skerman

Given an undirected $n$-vertex graph $G(V,E)$ and an integer $k$, let $T_k(G)$ denote the random vertex induced subgraph of $G$ generated by ordering $V$ according to a random permutation $\pi$ and including in $T_k(G)$ those vertices with…

Discrete Mathematics · Computer Science 2018-01-29 Uriel Feige , Jonathan Hermon , Daniel Reichman

For a graph G, let t(G) denote the maximum number of vertices in an induced subgraph of G that is a tree. In this paper, we study the problem of bounding t(G) for graphs which do not contain a complete graph K_r on r vertices. This problem…

Combinatorics · Mathematics 2008-10-25 Jacob Fox , Po-Shen Loh , Benny Sudakov

The induced arboricity of a graph $G$ is the smallest number of induced forests covering the edges of $G$. This is a well-defined parameter bounded from above by the number of edges of $G$ when each forest in a cover consists of exactly one…

Combinatorics · Mathematics 2017-06-01 Maria Axenovich , Daniel Goncalves , Jonathan Rollin , Torsten Ueckerdt

The bidimensionality of a set of vertices $X$ in a graph $G$ is the maximum $k$ for which $G$ contains as a $X$-rooted minor the $(k \times k)$-grid. This notion allows for the following version of the Graph Minors Structure Theorem (GMST)…

Combinatorics · Mathematics 2026-05-27 Dimitrios M. Thilikos , Sebastian Wiederrecht

Chudnovsky, Kim, Oum, and Seymour recently established that any prime graph contains one of a short list of induced prime subgraphs [1]. In the present paper we reprove their theorem using many of the same ideas, but with the key…

Logic · Mathematics 2015-11-10 M. Malliaris , C. Terry