# Sums of Kloosterman sums in arithmetic progressions, and the error term in the dispersion method

Abstract : We prove a bound for quintilinear sums of Kloosterman sums, with congruence conditions on the "smooth" summation variables. This generalizes classical work of Deshouillers and Iwaniec, and is key to obtaining power-saving error terms in applications, notably the dispersion method. As a consequence, assuming the Riemann hypothesis for Dirichlet $L$-functions, we prove a power-saving error term in the Titchmarsh divisor problem of estimating $\sum_{p\leq x}\tau(p-1)$. Unconditionally, we isolate the possible contribution of Siegel zeroes, showing it is always negative. Extending work of Fouvry and Tenenbaum, we obtain power-saving in the asymptotic formula for $\sum_{n\leq x}\tau_k(n)\tau(n+1)$, reproving a result announced by Bykovski\u{i} and Vinogradov by a different method. The gain in the exponent is shown to be independent of $k$ if a generalized Lindel\"of hypothesis is assumed.
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Journal articles

Cited literature [22 references]

https://hal.archives-ouvertes.fr/hal-01302604
Contributor : Sary Drappeau <>
Submitted on : Thursday, April 14, 2016 - 4:10:34 PM
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Sary Drappeau. Sums of Kloosterman sums in arithmetic progressions, and the error term in the dispersion method. Proceedings of the London Mathematical Society, London Mathematical Society, 2017, 114 (4), pp.684-732. ⟨10.1112/plms.12022⟩. ⟨hal-01302604⟩

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