{ "id": "1101.4715", "version": "v3", "published": "2011-01-25T04:12:31.000Z", "updated": "2011-03-30T08:02:51.000Z", "title": "Extremal incomplete sets in finite abelian groups", "authors": [ "Dan Guo", "Yongke Qu", "Guoqing Wang", "Qinghong Wang" ], "comment": "Swith some notations into ones which are more popular and put the materials of Appendix into the body. The present version is to appear in Ars Combinatoria", "categories": [ "math.CO", "math.NT" ], "abstract": "Let $G$ be a finite abelian group. The critical number ${\\rm cr}(G)$ of $G$ is the least positive integer $\\ell$ such that every subset $A\\subseteq G\\setminus\\{0\\}$ of cardinality at least $\\ell$ spans $G$, i.e., every element of $G$ can be written as a nonempty sum of distinct elements of $A$. The exact values of the critical number have been completely determined recently for all finite abelian groups. The structure of these sets of cardinality ${\\rm cr}(G)-1$ which fail to span $G$ has also been characterized except for the case that $|G|$ is an even number and the case that $|G|=pq$ with $p,q$ are primes. In this paper, we characterize these extremal subsets for $|G|\\geq 36$ is an even number, or $|G|=pq$ with $p,q$ are primes and $q\\geq 2p+3$.", "revisions": [ { "version": "v3", "updated": "2011-03-30T08:02:51.000Z" } ], "analyses": { "keywords": [ "finite abelian group", "extremal incomplete sets", "critical number", "extremal subsets", "exact values" ], "note": { "typesetting": "TeX", "pages": 0, "language": "en", "license": "arXiv", "status": "editable", "adsabs": "2011arXiv1101.4715G" } } }