A discrete mean value of the Riemann zeta function

Abstract

In this work, we estimate the sum \begin{align*} \sum_{0 < \Im(\rho) \leq T} \zeta(\rho+\alpha)X(\rho) Y(1\!-\! \rho) \end{align*} over the nontirival zeros $\rho$ of the Riemann zeta funtion where $\alpha$ is a complex number with $\alpha\ll 1/\log T$ and $X(\cdot)$ and $Y(\cdot)$ are some Dirichlet polynomials. Moreover, we estimate the discrete mean value above for higher derivatives where $\zeta(\rho+\alpha)$ is replaced by $\zeta^{(m)}(\rho)$ for all $m\in\mathbb{N}$. The formulae we obtain generalize a number of previous results in the literature. As an application, assuming the Riemann Hypothesis we obtain the lower bound \begin{align*} \sum_{0 < \Im(\rho) < T} | \zeta^{(m)}(\rho)|^{2k} \gg T(\log T)^{k^2+2km+1} \quad \quad (k,m\in\mathbb{N}) \end{align*} which was previously known under the Generalized Riemann Hypothesis, in the case $m=1$.