Stratification and averaging for exponential sums: bilinear forms with generalized Kloosterman sums

Fuente: arXiv
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Autores principales: Kowalski, E., Michel, Ph., Sawin, W.
Formato: Preprint
Publicado: 2018
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author Kowalski, E.
Michel, Ph.
Sawin, W.
author_facet Kowalski, E.
Michel, Ph.
Sawin, W.
contents We prove non-trivial bounds for bilinear forms with hyper-Kloosterman sums with characters modulo a prime $q$ which, for both variables of length $M$, are non-trivial as soon as $M\geq q^{3/8+δ}$ for any $δ>0$. This range, which matches Burgess's range, is identical with the best results previously known only for simpler exponentials of monomials. The proof combines refinements of the analytic tools from our previous paper and new geometric methods. The key geometric idea is a comparison statement that shows that even when the "sum-product" sheaves that appear in the analysis fail to be irreducible, their decomposition reflects that of the "input" sheaves, except for parameters in a high-codimension subset. This property is proved by a subtle interplay between étale cohomology in its algebraic and diophantine incarnations. We prove a first application concerning the first moment of a family of $L$-functions of degree $3$.
format Preprint
id arxiv_https___arxiv_org_abs_1802_09849
institution arXiv
publishDate 2018
record_format arxiv
spellingShingle Stratification and averaging for exponential sums: bilinear forms with generalized Kloosterman sums
Kowalski, E.
Michel, Ph.
Sawin, W.
Number Theory
Algebraic Geometry
11T23, 11L05, 11Mxx, 11N37, 11N75, 11F66, 14F20, 14D05
We prove non-trivial bounds for bilinear forms with hyper-Kloosterman sums with characters modulo a prime $q$ which, for both variables of length $M$, are non-trivial as soon as $M\geq q^{3/8+δ}$ for any $δ>0$. This range, which matches Burgess's range, is identical with the best results previously known only for simpler exponentials of monomials. The proof combines refinements of the analytic tools from our previous paper and new geometric methods. The key geometric idea is a comparison statement that shows that even when the "sum-product" sheaves that appear in the analysis fail to be irreducible, their decomposition reflects that of the "input" sheaves, except for parameters in a high-codimension subset. This property is proved by a subtle interplay between étale cohomology in its algebraic and diophantine incarnations. We prove a first application concerning the first moment of a family of $L$-functions of degree $3$.
title Stratification and averaging for exponential sums: bilinear forms with generalized Kloosterman sums
topic Number Theory
Algebraic Geometry
11T23, 11L05, 11Mxx, 11N37, 11N75, 11F66, 14F20, 14D05
url https://arxiv.org/abs/1802.09849