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We prove that every 3-connected planar graph on $n$ vertices contains an induced path on $\Omega(\log n)$ vertices, which is best possible and improves the best known lower bound by a multiplicative factor of $\log \log n$. We deduce that…

Combinatorics · Mathematics 2016-12-20 Louis Esperet , Laetitia Lemoine , Frédéric Maffray

A path cover of a graph is a set of disjoint paths so that every vertex in the graph is contained in one of the paths. The path cover number $p(G)$ of graph $G$ is the cardinality of a path cover with the minimum number of paths. Reed in…

Combinatorics · Mathematics 2018-06-20 Gexin Yu

Let $D$ be a digraph. A collection of disjoint sets of vertices (respec., collection of disjoint subdigraphs) $\mathcal{H}$ of $D$ and a vertex subset (or subdigraph) $Q$ of $D$ are orthogonal if every set (respec., subdigraph) $H \in…

Combinatorics · Mathematics 2026-05-12 Caroline A. de Paula Silva , Cândida Nunes da Silva , Orlando Lee

For a simple graph $G$, the $3$-distance graph, $D_3(G)$, is a graph with the vertex set $V(G)$ and two vertices are adjacent if and only if their distance is $3$ in the graph $G$. For a connected graph $G$, we provide some conditions for…

Combinatorics · Mathematics 2024-03-12 S. R. Musawi , S. H. Jafari

In this paper we consider Contact graphs of Paths on a Grid (CPG graphs), i.e. graphs for which there exists a family of interiorly disjoint paths on a grid in one-to-one correspondence with their vertex set such that two vertices are…

Computational Geometry · Computer Science 2018-09-07 Zakir Deniz , Esther Galby , Andrea Munaro , Bernard Ries

Let $G$ be a graph of order $n$. A path decomposition $\mathcal{P}$ of $G$ is a collection of edge-disjoint paths that covers all the edges of $G$. Let $p(G)$ denote the minimum number of paths needed in a path decomposition of $G$. Gallai…

Combinatorics · Mathematics 2023-10-19 Xiaohong Chen , Baoyindureng Wu

We make progress toward a characterization of the graphs $H$ such that every connected $H$-free graph has a longest path transversal of size $1$. In particular, we show that the graphs $H$ on at most $4$ vertices satisfying this property…

Combinatorics · Mathematics 2025-04-23 James A. Long , Kevin G. Milans , Andrea Munaro

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

Let $G$ be a graph of order $n$. A path decomposition $\mathcal{P}$ of $G$ is a collection of edge-disjoint paths that covers all the edges of $G$. Let $p(G)$ denote the minimum number of paths needed in a path decomposition of $G$. Gallai…

Combinatorics · Mathematics 2023-10-18 Xiaohong Chen , Baoyindureng Wu

Gallai's path decomposition conjecture states that if $G$ is a connected graph on $n$ vertices, then the edges of $G$ can be decomposed into at most $\lceil \frac{n }{2} \rceil$ paths. A graph is said to be an odd semi-clique if it can be…

Combinatorics · Mathematics 2024-02-14 Nevil Anto , Manu Basavaraju

A famous conjecture by Itai and Zehavi states that, for every $d$-vertex-connected graph $G$ and every vertex $r$ in $G$, there are $d$ spanning trees of $G$ such that, for every vertex $v$ in $G\setminus \{r\}$, the paths between $r$ and…

Combinatorics · Mathematics 2025-07-01 Lawrence Hollom , Lyuben Lichev , Adva Mond , Julien Portier , Yiting Wang

Flip graphs of non-crossing configurations in the plane are widely studied objects, e.g., flip graph of triangulations, spanning trees, Hamiltonian cycles, and perfect matchings. Typically, it is an easy exercise to prove connectivity of a…

Computational Geometry · Computer Science 2024-07-08 Linda Kleist , Peter Kramer , Christian Rieck

Consider a connected graph $G$ and let $T$ be a spanning tree of $G$. Every edge $e \in G-T$ induces a cycle in $T \cup \{e\}$. The intersection of two distinct such cycles is the set of edges of $T$ that belong to both cycles. The MSTCI…

Combinatorics · Mathematics 2024-04-23 Manuel Dubinsky , César Massri , Gabriel Taubin

In this paper, we prove a tight minimum degree condition in general graphs for the existence of paths between two given endpoints, whose lengths form a long arithmetic progression with common difference one or two. This allows us to obtain…

Combinatorics · Mathematics 2021-01-27 Jun Gao , Qingyi Huo , Chun-Hung Liu , Jie Ma

We shall study degree-monotone paths in graphs, a problem inspired by the celebrated theorem of Erd{\H{o}}s-Szekeres concerning the longest monotone subsequence of a given sequence of numbers. A path P in a graph G is said to be a degree…

Combinatorics · Mathematics 2014-05-09 Yair Caro , Josef Lauri , Christina Zarb

Given a finite set $ S $ of points, we consider the following reconfiguration graph. The vertices are the plane spanning paths of $ S $ and there is an edge between two vertices if the two corresponding paths differ by two edges (one…

Computational Geometry · Computer Science 2024-07-02 Valentino Boucard , Guilherme D. da Fonseca , Bastien Rivier

Dirac showed that in a $(k-1)$-connected graph there is a path through each $k$ vertices. The path $k$-connectivity $\pi_k(G)$ of a graph $G$, which is a generalization of Dirac's notion, was introduced by Hager in 1986. In this paper, we…

Combinatorics · Mathematics 2016-03-15 Yaping Mao

An extension of an induced path $P$ in a graph $G$ is an induced path $P'$ such that deleting the endpoints of $P'$ results in $P$. An induced path in a graph is said to be avoidable if each of its extensions is contained in an induced…

Combinatorics · Mathematics 2021-10-22 Vladimir Gurvich , Matjaž Krnc , Martin Milanič , Mikhail Vyalyi

The problem of finding paths in temporal graphs has been recently considered due to its many applications. In this paper we consider a variant of the problem that, given a vertex-colored temporal graph, asks for a path whose vertices have…

Data Structures and Algorithms · Computer Science 2021-09-06 Riccardo Dondi , Mohammad Mehdi Hosseinzadeh

A long-standing conjecture of Thomassen says that every longest cycle of a $3$-connected graph has a chord. Thomassen (2018) proved that if $G$ is $2$-connected and cubic, then any longest cycle must have a chord. He also showed that if $G$…

Combinatorics · Mathematics 2025-02-18 Haidong Wu , Shunzhe Zhang