Abstract
For set \(A\subset \mathbb{F}_p^*\) define by \(\mathsf{sf}(A)\) the size of the largest sum-free subset of A. Alon and Kleitman [3] showed that \(\mathsf{sf} (A) \ge |A|/3+O(|A|/p)\). We prove that if \(\mathsf{sf}(A)-|A|/3\) is small then the set A must be uniformly distributed on cosets of each large multiplicative subgroup. Our argument relies on irregularity of distribution of multiplicative subgroups on certain intervals in \(\mathbb{F}p\).
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Acknowledgements
We would like to thank Alexander Kalmynin for very useful conversation about distribution of quadratic residues and Mateusz for linguistic correction of the manuscript.
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Dedicated to the 80th birthday of Endre Szemerédi
The first named author is supported by National Science Centre, Poland grant 2019/35/B/ST1/00264.
Research supported by the grant of the Russian Government N 075-15-2019-1926.
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Schoen, T., Shkredov, I.D. L-functions and sum-free sets. Acta Math. Hungar. 161, 427–442 (2020). https://doi.org/10.1007/s10474-020-01055-0
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DOI: https://doi.org/10.1007/s10474-020-01055-0