Hardy-Littlewood-Riesz type equivalent criteria for the Generalized Riemann hypothesis

TL;DR

This paper establishes an equivalence between the generalized Riemann hypothesis and a specific asymptotic bound involving Dirichlet characters, the Möbius function, and exponential decay, extending classical bounds by Riesz and Hardy-Littlewood.

Contribution

It introduces a new criterion for the generalized Riemann hypothesis based on a generalized bound involving exponential sums with Dirichlet characters and the Möbius function.

Findings

The generalized Riemann hypothesis is equivalent to a specific asymptotic bound.

The bound extends classical results by Riesz and Hardy-Littlewood.

The criterion involves exponential sums with Dirichlet characters and the Möbius function.

Abstract

In the present paper, we prove that the generalized Riemann hypothesis for the Dirichlet $L$-function $L(s,\chi)$ is equivalent to the following bound: Let $k \geq 1$ and $\ell$ be positive real numbers. For any $\epsilon >0$, we have \begin{align*} \sum_{n=1}^{\infty} \frac{\chi(n) \mu(n)}{n^{k}} \exp \left(- \frac{ x}{n^{\ell}}\right) = O_{\epsilon,k,\ell} \bigg(x^{-\frac{k}{\ell}+\frac{1}{2 \ell} + \epsilon }\bigg), \quad \mathrm{as}\,\, x \rightarrow \infty, \end{align*} where $\chi$ is a primitive Dirichlet character modulo $q$, and $\mu(n)$ denotes the M\"{o}bius function. This bound generalizes the previous bounds given by Riesz, and Hardy-Littlewood.