English

Some questions on entangled linear orders

Logic 2026-04-22 v2 Combinatorics

Abstract

Entangled linear orders were first introduced by Abraham and Shelah. Todor\v{c}evi\'c showed that these linear orders exist under CH\mathsf{CH}. We prove the following results: (1) If CH\mathsf{CH} holds, then, for every n>0n > 0, there is an nn-entangled linear order which is not (n+1)(n+1)-entangled. (2) If CH\mathsf{CH} holds, then there are two homeomorphic sets of reals A,BRA, B \subseteq \mathbb{R} such that AA is entangled but BB is not 22-entangled. (3) If RL\mathbb{R}\subseteq \mathrm{L}, then there is an entangled Π11\Pi_1^1 set of reals. (4) If \diamondsuit holds, then there is a 22-entangled non-separable linear order.

Keywords

Cite

@article{arxiv.2507.17503,
  title  = {Some questions on entangled linear orders},
  author = {Raphaël Carroy and Maxwell Levine and Lorenzo Notaro},
  journal= {arXiv preprint arXiv:2507.17503},
  year   = {2026}
}

Comments

27 pages

R2 v1 2026-07-01T04:15:15.777Z