Amending the Lonely Runner Spectrum Conjecture

Abstract

Let $\lVert x \rVert$ be the absolute distance from $x$ to the nearest integer. For a set of distinct positive integer speeds $v_1, \ldots, v_n$, we define its maximum loneliness, also known as the gap $\delta$, to be
$$\text{ML}(v_1,\ldots,v_n) = \delta(v_1,\ldots,v_n) = \max_{t \in \mathbb{R}}\min_{1 \leq i \leq n} \lVert tv_i \rVert.$$
The Loneliness Spectrum Conjecture, recently proposed by Kravitz, asserts that $$\exists s \in \mathbb{N}, \text{ML}(v_1,\ldots,v_n) = \frac{s} {sn + 1} \text{ or } \text{ML}(v_1,\ldots,v_n) \geq \frac{1}{n}.$$
We disprove the Loneliness Spectrum Conjecture for $n = 4$ with an infinite family of counterexamples and propose an alternative conjecture. We confirm the amended conjecture for $n = 4$ whenever there exists a pair of speeds with a common factor of at least $3$ and prove some related results.