Abstract

We prove that for a large class of multiplicative functions, referred to as generalized divisor functions, it is possible to find a lower bound for the corresponding variance in arithmetic progressions. As a main corollary, we deduce such a result for any alpha -fold divisor function, for any complex number alpha not in {1}cup -mathbb {N}, even when considering a sequence of parameters alpha close in a proper way to 1. Our work builds on that of Harper and Soundararajan, who handled the particular case of k-fold divisor functions d_k(n), with kin mathbb {N}_{ge 2}.

Highlights

  • Let f be a complex arithmetic function

  • For the k-th divisor function dk (n) = e1e2...ek=n 1, which counts all the possible ways of decomposing n into a product of k positive integers, a conjecture on the asymptotic behaviour of its variance in arithmetic progressions has been suggested in the work of Keating et al [15]

  • For another instance of this see the paper of Gorodetsky and Rodgers [10], in which the authors provided a prediction on the behaviour of the variance in arithmetic progressions of the indicator function of sums of two squares

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Summary

Introduction

Let f be a complex arithmetic function. It is believed that many f are roughly uniformly distributed in arithmetic progressions, or equivalently that there is an. The present work has been conducted when the author was a first year PhD student at the University of Warwick. Data sharing not applicable to this article as no datasets were generated or analysed during the current study

B Daniele Mastrostefano
Statement of the main results
Lower bounding the integral over the minor arcs
Mean value of multiplicative functions under a coprimality condition
Twisting with Ramanujan’s sums
The contribution from small prime factors
The contribution from large prime factors
Combining the different pieces
11.1 Collecting the main results
11.3 The main term
11.4 Removal of some extra conditions
11.5 The estimate of the sum over s
11.6 The estimate of the sum over t
Full Text
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