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The variance of divisor sums in arithmetic progressions

  • Brad Rodgers EMAIL logo and Kannan Soundararajan
Published/Copyright: June 17, 2017

Abstract

We study the variance of sums of the k-fold divisor function dk(n) over sparse arithmetic progressions, with averaging over both residue classes and moduli. In a restricted range, we confirm an averaged version of a recent conjecture about the asymptotics of this variance. This result is closely related to moments of Dirichlet L-functions, and our proof relies on the asymptotic large sieve.


Communicated by Jan Bruinier


Award Identifier / Grant number: DMS 1500237

Funding statement: The second author is partially supported through a grant from the National Science Foundation (NSF DMS 1500237) and a Simons Investigator grant from the Simons Foundation.

Acknowledgements

We thank Adam Harper for a discussion which prompted us to think about this problem, and Régis de la Bretèche along with an anonymous referee for corrections. Some of the research for this paper was done while the first author was visiting Stanford University, which he thanks for its gracious hospitality.

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Received: 2016-11-5
Revised: 2017-4-20
Published Online: 2017-6-17
Published in Print: 2018-3-1

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