More (shifted) runners, less loneliness

Abstract

The shifted lonely runner conjecture was recently disproved by Blanco, Criado and Santos. We give quantitative bounds on its failure as the number of runners grows. The loneliness of a configuration is the maximum, over time, of the distance from the origin to the nearest runner. We write $1/(n+1+E_n)$ for the infimum of loneliness over configurations of $n$ runners on the unit circle with distinct positive integer velocities and arbitrary initial shifts. We prove $E_n\ge\lfloor n/287\rfloor$, which together with the elementary bound $E_n\leq n-1$ implies that $E_n$ grows linearly in $n$. We also show that $E_n\geq1$ for every $n\geq95$.