On character sums over flat numbers

Abstract

Let $q⩾2$ be an integer, $\chi$ be any non-principal character mod $q$, and $H=H(q)⩽q.$ In this paper the authors prove some estimates for character sums of the form \[\mathcal{W}(χ,H;q)=\sum_{n\in\mathscr{F}(H)}χ(n),\] where \[\mathscr{F}(H)=\left\{n\in\mathbb{Z}|(n,q)=1,1\leqslant n,\bar{n}\leqslant q, |n-\bar{n}|\leqslant H\},\] $\bar{n}$ is defined by $n\bar{n}\equiv 1(\mathrm{mod}q).$

arXiv comment9 pages, with a complete proof of Theorem 3, Section 5. Accepted by J. Number Theory