On the cardinality of sumsets in torsion‐free groups

Let A, B be finite subsets of a torsion‐free group G. We prove that, for every positive integer k, there is a c(k) such that if |B| ⩾ c(k), then the inequality |AB| ⩾ |A|+|B|+k holds unless a left translate of A is contained in a cyclic subgroup. We obtain c(k) < c0k6 for arbitrary torsion‐free g...

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Veröffentlicht in:The Bulletin of the London Mathematical Society 2012-10, Vol.44 (5), p.1034-1041
Hauptverfasser: Böröczky, Károly J., Pálfy, Péter P., Serra, Oriol
Format: Artikel
Sprache:eng
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Zusammenfassung:Let A, B be finite subsets of a torsion‐free group G. We prove that, for every positive integer k, there is a c(k) such that if |B| ⩾ c(k), then the inequality |AB| ⩾ |A|+|B|+k holds unless a left translate of A is contained in a cyclic subgroup. We obtain c(k) < c0k6 for arbitrary torsion‐free groups, and c(k)
ISSN:0024-6093
1469-2120
DOI:10.1112/blms/bds032