English

On the few products, many sums problem

Combinatorics 2017-12-04 v1

Abstract

We prove new results on additive properties of finite sets AA with small multiplicative doubling AAMA|AA|\leq M|A| in the category of real/complex sets as well as multiplicative subgroups in the prime residue field. The improvements are based on new combinatorial lemmata, which may be of independent interest. Our main results are the inequality AA3AA5A10, |A-A|^3|AA|^5 \gtrsim |A|^{10}, over the reals, "redistributing" the exponents in the textbook Elekes sum-product inequality and the new best known additive energy bound E(A)MA49/20\mathsf E(A)\lesssim_M |A|^{49/20}, which aligns, in a sense to be discussed, with the best known sum set bound A+AMA8/5|A+A|\gtrsim_M |A|^{8/5}. These bounds, with M=1M=1, also apply to multiplicative subgroups of Fp×\mathbb F^\times_p, whose order is O(p)O(\sqrt{p}). We adapt the above energy bound to larger subgroups and obtain new bounds on gaps between elements in cosets of subgroups of order Ω(p)\Omega(\sqrt{p}).

Keywords

Cite

@article{arxiv.1712.00410,
  title  = {On the few products, many sums problem},
  author = {Brendan Murphy and Misha Rudnev and Ilya D. Shkredov and Yurii N. Shteinikov},
  journal= {arXiv preprint arXiv:1712.00410},
  year   = {2017}
}

Comments

27pp

R2 v1 2026-06-22T23:03:57.328Z