English

On two questions about restricted sumsets in finite abelian groups

Number Theory 2016-07-20 v1

Abstract

Let GG be an abelian group of finite order nn, and let hh be a positive integer. A subset AA of GG is called {\em weakly hh-incomplete}, if not every element of GG can be written as the sum of hh distinct elements of AA; in particular, if AA does not contain hh distinct elements that add to zero, then AA is called {\em weakly hh-zero-sum-free}. We investigate the maximum size of weakly hh-incomplete and weakly hh-zero-sum-free sets in GG, denoted by Ch(G)C_h(G) and Zh(G)Z_h(G), respectively. Among our results are the following: (i) If GG is of odd order and (n1)/2hn2(n-1)/2 \leq h \leq n-2, then Ch(G)=Zh(G)=h+1C_h(G)=Z_h(G)=h+1, unless GG is an elementary abelian 3-group and h=n3h=n-3; (ii) If GG is an elementary abelian 2-group and n/2hn2n/2 \leq h \leq n-2, then Ch(G)=Zh(G)=h+2C_h(G)=Z_h(G)=h+2, unless h=n4h=n-4.

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Cite

@article{arxiv.1607.05718,
  title  = {On two questions about restricted sumsets in finite abelian groups},
  author = {Béla Bajnok and Samuel Edwards},
  journal= {arXiv preprint arXiv:1607.05718},
  year   = {2016}
}

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15 pages