English

The critical number of finite abelian groups

Number Theory 2008-10-20 v1

Abstract

Let G be an additive, finite abelian group. The critical number cr(G)\mathsf{cr}(G) of GG is the smallest positive integer \ell such that for every subset SG{0}S \subset G \setminus \{0\} with S|S| \ge \ell the following holds: Every element of GG can be written as a nonempty sum of distinct elements from SS. The critical number was first studied by P. Erd\H{o}s and H. Heilbronn in 1964, and due to the contributions of many authors the value of cr(G)\mathsf {cr}(G) is known for all finite abelian groups GG except for GZ/pqZG \cong \mathbb{Z}/pq\mathbb{Z} where p,qp,q are primes such that p+2p2+1<q<2pp+\lfloor2\sqrt{p-2}\rfloor+1<q<2p. We determine that cr(G)=p+q2\mathsf {cr}(G)=p+q-2 for such groups.

Keywords

Cite

@article{arxiv.0810.3223,
  title  = {The critical number of finite abelian groups},
  author = {Michael Freeze and Weidong Gao and Alfred Geroldinger},
  journal= {arXiv preprint arXiv:0810.3223},
  year   = {2008}
}