English
Related papers

Related papers: Cops and robbers on $2K_2$-free graphs

200 papers

The lower bound W(K_{2n})>=3n-2 is proved for the greatest possible number of colors in an interval edge coloring of the complete graph K_{2n}.

Discrete Mathematics · Computer Science 2007-12-18 Rafael R. Kamalian , Petros A. Petrosyan

The game of Cops and Robber is a pursuit-evasion game which is usually played on a connected graph. In the game, a set of cops and a robber move around the vertices of a graph along edges, where the cops aim to capture the robber, while the…

Combinatorics · Mathematics 2021-07-27 Pinkaew Siriwong , Ratinan Boonklurb , Henry Liu , Sirirat Singhun

We prove that every subcubic triangle-free graph has fractional chromatic number at most 14/5, thus confirming a conjecture of Heckman and Thomas [A new proof of the independence ratio of triangle-free cubic graphs. Discrete Math. 233…

Combinatorics · Mathematics 2017-05-17 Zdeněk Dvořák , Jean-Sébastien Sereni , Jan Volec

We introduce the game of Cops and Eternal Robbers played on graphs, where there are infinitely many robbers that appear sequentially over distinct plays of the game. A positive integer $t$ is fixed, and the cops are required to capture the…

Discrete Mathematics · Computer Science 2020-03-11 Anthony Bonato , Melissa Huggan , Trent Marbach , Fionn Mc Inerney

Problem of finding an optimal upper bound for the chromatic no. of a (3 Times K1)-free graph is still open and pretty hard. Here we prove that for a (3 Times K1)-free graph G with maximum degree greater than or equal to 8, {\chi} is less…

Combinatorics · Mathematics 2017-02-28 Medha Dhurandhar

The cops and robbers game has been extensively studied under the assumption of optimal play by both the cops and the robbers. In this paper we study the problem in which cops are chasing a drunk robber (that is, a robber who performs a…

Discrete Mathematics · Computer Science 2017-01-09 Athanasios Kehagias , Pawel Pralat

We investigate extremal graphs related to the game of Cops and Robbers. We focus on graphs where a single cop can catch the robber; such graphs are called cop-win. The capture time of a cop-win graph is the minimum number of moves the cop…

Combinatorics · Mathematics 2019-03-21 David Offner , Kerry Ojakian

We investigate multiple variants of the game Cops and Robbers. Playing it on an $n \times n$ toroidal chess graph, the game is varied by defining moves for cops and robbers differently, always mimicking moves of certain chess pieces. In…

Combinatorics · Mathematics 2018-10-26 Allyson Hahn , Neil R. Nicholson

For a graph $G$, let $f_2(G)$ denote the largest number of vertices in a $2$-regular subgraph of $G$. We determine the minimum of $f_2(G)$ over $3$-regular $n$-vertex simple graphs $G$. To do this, we prove that every $3$-regular multigraph…

Combinatorics · Mathematics 2019-03-22 Ilkyoo Choi , Ringi Kim , Alexandr Kostochka , Boram Park , Douglas B. West

We provide a sublinear bound on the cop throttling number of a connected graph. Related to the graph searching game Cops and Robbers, the cop throttling number, written $\mathrm{th}_c(G)$, is given by…

Combinatorics · Mathematics 2019-01-28 Anthony Bonato , Sean English

A 2-hued coloring of a graph $G$ (also known as conditional $(k, 2)$-coloring and dynamic coloring) is a coloring such that for every vertex $v\in V(G)$ of degree at least $2$, the neighbors of $v$ receive at least $2$ colors. The smallest…

Combinatorics · Mathematics 2017-02-06 Arash Ahadi , Ali Dehghan

We consider a variation of Cops and Robber, introduced in [D. Cox and A. Sanaei, The damage number of a graph, [Aust. J. of Comb. 75(1) (2019) 1-16] where vertices visited by a robber are considered damaged and a single cop aims to minimize…

Combinatorics · Mathematics 2024-12-19 Melissa A. Huggan , Margaret-Ellen Messinger , Amanda Porter

Let $\mathcal{C}_k(n)$ be the family of all connected $k$-chromatic graphs of order $n$. Given a natural number $x\geq k$, we consider the problem of finding the maximum number of $x$-colorings among graphs in $\mathcal{C}_k(n)$. When…

Combinatorics · Mathematics 2018-05-25 Aysel Erey

The cop throttling number of a graph, introduced in 2018 by Breen et al., optimizes the balance between the number of cops used and the number of rounds required to catch the robber in a game of Cops and Robbers. In 2019, Cox and Sanaei…

Combinatorics · Mathematics 2020-07-14 Joshua Carlson , Robin Eagleton , Jesse Geneson , John Petrucci , Carolyn Reinhart , Preetul Sen

A graph is called $2K_2$-free if it does not contain two independent edges as an induced subgraph. Broersma, Patel, and Pyatkin showed that every 25-tough $2K_2$-free graph with at least three vertices is hamiltonian. In this paper, we…

Combinatorics · Mathematics 2017-06-29 Songling Shan

We consider a variant of Cops and Robbers wherein each edge traversed by the robber is deleted from the graph. The focus is on determining the minimum number of cops needed to capture a robber on a graph $G$, called the {\em bridge-burning…

Combinatorics · Mathematics 2018-12-27 William B. Kinnersley , Eric Peterson

We study the problem of cops and robbers on the grid where the robber is allowed to move faster than the cops. It is well known that two cops are necessary and sufficient to catch the robber on any finite grid when the robber has unit…

Combinatorics · Mathematics 2017-06-06 Paul Balister , Béla Bollobás , Bhargav Narayanan , Amy Shaw

We consider the effect on the length of the game of Cops and Robbers when more cops are added to the game play. In Overprescribed Cops and Robbers, as more cops are added, the capture time (the minimum length of the game assuming optimal…

Combinatorics · Mathematics 2016-11-24 Anthony Bonato , Xavier Pérez-Giménez , Paweł Prałat , Benjamin Reiniger

We consider the following generalized Tur\'an problem: For $2 \le s \le t$, what is the maximum number of triangles in a $K_{1,s,t}$-free graph on $n$ vertices? The previously best known lower and upper bounds are $\Omega(n^2)$ and…

Combinatorics · Mathematics 2025-08-15 Asier Calbet , Ritesh Goenka

The well-known 1-2-3 Conjecture asserts that the edges of every graph without isolated edges can be weighted with $1$, $2$ and $3$ so that adjacent vertices receive distinct weighted degrees. This is open in general. We prove that every…

Combinatorics · Mathematics 2018-03-21 Julien Bensmail , Jakub Przybyło