Estimates for trilinear and quadrilinear character sums
Étienne Fouvry
Université Paris-Saclay, Orsay Cedex, FranceIgor E. Shparlinski
University of New South Wales, Sydney, AustraliaPing Xi
Xi’an Jiaotong University, Xi’an, P. R. China

Abstract
We obtain new bounds on some trilinear and quadrilinear character sums, which are non-trivial starting from very short ranges of the variables. An application to an apparently new problem on oscillations of characters on differences between Farey fractions is given. Other applications include a modular analogue of a multiplicative hybrid problem of Iwaniec and Sárközy (1987) and the solvability of some prime type equations with constraints.
Cite this article
Étienne Fouvry, Igor E. Shparlinski, Ping Xi, Estimates for trilinear and quadrilinear character sums. Rev. Mat. Iberoam. (2025), published online first
DOI 10.4171/RMI/1530