Generalisations of the Landau--Gonek Theorem and applications to mean values of zeta
Benjamin Durkan, Christopher Hughes, Andrew Pearce-Crump
TL;DR
The work generalizes Landau–Gonek-style sums by weighting the non-trivial zeros of the Riemann zeta function with the functional equation factor $\chi(\rho)$ and the term $X^{\rho}$, establishing a uniform asymptotic for the three regimes of $X$ relative to the height $T$. The authors develop a stationary-phase-based analysis of a pivotal integral $J(\sigma,r,T)$ and a contour-analytic evaluation of the explicit formula, then leverage the approximate functional equation to control discrete moments of $\zeta$ and its derivatives. The main result, Theorem mainthm, yields explicit, region-dependent main terms and sharp error bounds, enabling rigorous proofs of Shanks' conjecture and its generalisation via mean-value arguments. This advances the understanding of how the arithmetic nature of $X$ influences zero-sum formulas and discrete moments, with implications for precise evaluations of $\zeta$-moments and zeta-derivative sums.
Abstract
The Landau--Gonek Theorem evaluates $X^ρ$ summed over the non-trivial zeros of the Riemann zeta function. Their result shows great sensitivity to the arithmetic nature of $X$. We prove a related result concerning the sum of $χ(ρ) X^ρ$ over the zeros of zeta, where $χ(s)$ is the term arising in the functional equation for the zeta function. Again, this result depends deeply on whether $X$ is an integer or not. We show the result splits into three cases, depending on whether $X$ is smaller than $T$, about the same size as $T$, or bigger than $T$. The reason this result is useful is that it easily permits the calculation of discrete moments of the Riemann zeta function via the approximate functional equation. As an application of this result, we provide an alternative proof of Shanks' conjecture.
