{ "id": "0810.3223", "version": "v1", "published": "2008-10-17T19:03:21.000Z", "updated": "2008-10-17T19:03:21.000Z", "title": "The critical number of finite abelian groups", "authors": [ "Michael Freeze", "Weidong Gao", "Alfred Geroldinger" ], "categories": [ "math.NT" ], "abstract": "Let G be an additive, finite abelian group. The critical number $\\mathsf{cr}(G)$ of $G$ is the smallest positive integer $\\ell$ such that for every subset $S \\subset G \\setminus \\{0\\}$ with $|S| \\ge \\ell$ the following holds: Every element of $G$ can be written as a nonempty sum of distinct elements from $S$. 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 $\\mathsf {cr}(G)$ is known for all finite abelian groups $G$ except for $G \\cong \\mathbb{Z}/pq\\mathbb{Z}$ where $p,q$ are primes such that $p+\\lfloor2\\sqrt{p-2}\\rfloor+1