English

Large subsets avoiding algebraic patterns

Combinatorics 2026-03-16 v2

Abstract

We prove the existence of a subset of the torus with large sumsets and avoiding all linear patterns. This extends a result of K\"orner, who had shown that for any integer q1q \geq 1, there exists a subset KK of R/Z\mathbb R/\mathbb Z satisfying no non-trivial linear relations of order 2q12q-1 and such that q.Kq.K has positive Lebesgue measure. Our method is based on transfinite induction, which also allows us to produce large sets in different senses (cardinality, outer Lebesgue measure or Hausdorff dimension) avoiding families of algebraic patterns, for example Sidon sets in infinite abelian groups with small 22 and 33-torsion or sets with no repeated distances in Rn\mathbb R^n. We also discuss questions of measurability of such sets and the role of the axiom of choice in our constructions.

Keywords

Cite

@article{arxiv.2503.22630,
  title  = {Large subsets avoiding algebraic patterns},
  author = {Alexandre Bailleul and Robin Riblet},
  journal= {arXiv preprint arXiv:2503.22630},
  year   = {2026}
}

Comments

15 pages. Fixed an incorrect argument about measurability and a few typos. Sections were rearranged