The fractional chromatic number of the plane is at least 4

Máté Matolcsi, Imre Z. Ruzsa, Dániel Varga +1

We prove that the fractional chromatic number ${\chi }_f({\mathbb{R}}^2)$ of the unit distance graph of the Euclidean plane is greater than or equal to $4$. Interestingly, however, we canno…