English

On traces of randomly rolling polytopes

Combinatorics 2026-08-06 v1

Abstract

Let P\mathcal{P} be a three-dimensional convex polytope resting with one of its faces on the plane. At each step, P\mathcal{P} is allowed to roll over a randomly selected edge of the face currently lying on the plane, until the adjacent face comes to rest on the plane. The trace of P\mathcal{P} is the set of all points of the plane that can be reached by a vertex of P\mathcal{P}, starting from a fixed initial position and performing a finite sequence of rolls. We prove that if the trace of P\mathcal{P} has a convergent subsequence, then, with probability one, the set of points reached by the vertices of a randomly rolling copy of P\mathcal{P} is everywhere dense in the plane. This settles a conjecture of Hegyv\'ari.

Keywords

Cite

@article{arxiv.2608.05721,
  title  = {On traces of randomly rolling polytopes},
  author = {Kenneth Moore and János Pach},
  journal= {arXiv preprint arXiv:2608.05721},
  year   = {2026}
}

Comments

15 pages, 2 figures