Sum-product inequalities with perturbation
Combinatorics
2009-07-02 v1 Number Theory
Abstract
Suppose that A is a set of n real numbers, each at least 1 apart. Define the ``perturbed sum and product sets'' S and P to be the sums a + b + f(a,b) and products (a+g(a,b))(b+h(a,b)), where f, g, and h satisfy certain upper bounds in terms of the n, |a| and |b|. We develop almost best possible lower bounds on |P| + |S|, using the largest possible sizes of the ``perturbation parameters'' f(a,b), g(a,b) and h(a,b). Our proof uses Elekes's idea for bounding |A+A|+|A.A| from below, in combination with the Szemeredi-Trotter curve theorem (actually, a minor generalization of it) of Szekely, applied to certain polygonal arcs.
Cite
@article{arxiv.0907.0175,
title = {Sum-product inequalities with perturbation},
author = {Spencer Backman and Ernie Croot and Derrick Hart and Mariah Hamel},
journal= {arXiv preprint arXiv:0907.0175},
year = {2009}
}
Comments
11 pages