Thomas Bellitto ; Arnaud Pêcher ; Antoine Sédillot - On the density of sets of the Euclidean plane avoiding distance 1

dmtcs:5153 - Discrete Mathematics & Theoretical Computer Science, August 31, 2021, vol. 23 no. 1 - https://doi.org/10.46298/dmtcs.5153
On the density of sets of the Euclidean plane avoiding distance 1

Authors: Thomas Bellitto ; Arnaud Pêcher ; Antoine Sédillot

A subset $A \subset \mathbb R^2$ is said to avoid distance $1$ if: $\forall x,y \in A, \left\| x-y \right\|_2 \neq 1.$ In this paper we study the number $m_1(\mathbb R^2)$ which is the supremum of the upper densities of measurable sets avoiding distance 1 in the Euclidean plane. Intuitively, $m_1(\mathbb R^2)$ represents the highest proportion of the plane that can be filled by a set avoiding distance 1. This parameter is related to the fractional chromatic number $\chi_f(\mathbb R^2)$ of the plane. We establish that $m_1(\mathbb R^2) \leq 0.25647$ and $\chi_f(\mathbb R^2) \geq 3.8991$.


Volume: vol. 23 no. 1
Section: Combinatorics
Published on: August 31, 2021
Submitted on: January 31, 2019
Keywords: Mathematics - Metric Geometry,Computer Science - Discrete Mathematics,Mathematics - Combinatorics


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