English

An improved lower bound for the union-closed set conjecture

Combinatorics 2023-06-21 v3

Abstract

Gilmer has recently shown that in any nonempty union-closed family F\mathcal F of subsets of a finite set, there exists an element contained in at least a proportion .01.01 of the sets of F\mathcal F. We improve the proportion from .01.01 to 352.38\frac{ 3 -\sqrt{5}}{2} \approx .38 in this result. An improvement to 12\frac{1}{2} would be the Frankl union-closed set conjecture. We follow Gilmer's method, replacing one key estimate by a sharp estimate. We then suggest a new addition to this method and sketch a proof that it can obtain a constant strictly greater than 352\frac{ 3 -\sqrt{5}}{2} . We also disprove a conjecture of Gilmer that would have implied the union-closed set conjecture.

Keywords

Cite

@article{arxiv.2211.11504,
  title  = {An improved lower bound for the union-closed set conjecture},
  author = {Will Sawin},
  journal= {arXiv preprint arXiv:2211.11504},
  year   = {2023}
}

Comments

9 pages

R2 v1 2026-06-28T06:22:34.598Z