First Moment of Quadratic Hecke $L$-Functions with Lower Order Term
Peng Gao, Liangyi Zhao
TL;DR
This paper analyzes the first moment of the family of primitive quadratic Hecke L-functions in the Gaussian field $K=\mathbb{Q}(i)$ using the double Dirichlet series method. Under RH and the Lindelöf hypothesis, it proves meromorphic continuation and identifies explicit residue terms that generate a main term with secondary components in the asymptotics of the smoothed first moment, with an error term that is $O(X^{\varepsilon})$ smaller than the main contribution. The authors derive a central-value formula with a sharp $X^{1/4+\varepsilon}$-type error under GRH and show a distinct behavior for square-free conductors versus all conductors via a contour-shifting argument and careful residue calculations. The approach connects function-field intuition (as seen in Florea) with number-field phenomena (via Gaussian fields) and highlights the power of double Dirichlet series in isolating main and secondary terms for families of $L$-functions.
Abstract
We evaluate the first moment of the family of primitive quadratic Hecke $L$-functions in the Gaussian field using the method of double Dirichlet series under the Riemann hypothesis and the Lindelöf hypothesis. We obtain asymptotic formulas with secondary main terms and error terms of size that is one quarter of that of the main term.
