Spencer's Single Lonely Runner Conjecture

Let V={v1,,vn}V=\{v_1,\dots,v_n\} be an nn-set of pairwise distinct real speeds, and let x\|x\| denote the distance from xx to the nearest integer. Single Lonely Runner Conjecture. For every nNn\in\mathbb{N} and every such VV, there exist i[n]i\in[n] and tRt\in\mathbb{R} such that

minjit(vjvi)1n.\min_{j\neq i}\|t(v_j-v_i)\|\geq\frac{1}{n}.

This weakening, attributed to Joel Spencer, asks only for one runner to become lonely rather than requiring the assertion for every runner. It is presented as an open problem in the survey.

Sources & referencesView supporting material

Primary source

Guillem Perarnau and Oriol Serra, “The Lonely Runner Conjecture turns 60”, arXiv:2409.20160 (2025).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.