Euler Product Asymptotics for $L$-functions of Elliptic Curves
Arshay Sheth
TL;DR
This paper studies Euler-product asymptotics for $L$-functions of elliptic curves by analyzing partial Euler products in the right half of the critical strip under the Riemann Hypothesis for $L(E,s)$. It derives a precise expansion $\prod_{\substack{p\le x}}$ (local Euler factors) $= L(E,s) \exp(-r I_s(x) - R_s(x) + U_s(x) + O(\log x/x^{1/6}))$, with $I_s,R_s,U_s$ defined, and shows that there exists a finite-logarithmic-measure set $S$ such that $\prod_{p\le x} N_p/p \sim C (\log x)^r$ where $r=\mathrm{ord}_{s=1} L(E,s)$ and $C=\dfrac{r!}{L^{(r)}(E,1)} \sqrt{2} e^{r\gamma}$. This yields a robust link between the original OBSD conjecture and the modern BSD conjecture, recovering Goldfeld’s result and providing a partial converse, while leveraging an explicit-formula framework and a Gallagher-based refinement to control error terms. The work supplies a deeper understanding of how partial Euler products encode the rank and L-function behavior, with potential implications for the BSD–OBSD correspondence and related conjectures on Euler products. Overall, the paper advances the analytic study of Euler products for elliptic-curve L-functions and strengthens the connection between invariants predicted by BSD and their Euler-product manifestations.
Abstract
Let $E/\mathbb Q$ be an elliptic curve and for each prime $p$, let $N_p$ denote the number of points of $E$ modulo $p$. The original version of the Birch and Swinnerton-Dyer conjecture asserts that $\prod \limits _{p \leq x} \frac{N_p}{p} \sim C (\log x) ^{\text{rank}(E(\mathbb Q))}$ as $x \to \infty$. Goldfeld (1982) showed that this conjecture implies both the Riemann Hypothesis for $L(E, s)$ and the modern formulation of the conjecture i.e. that $\text{ord}_{s=1} L(E, s)= \text{rank}(E(\mathbb Q))$. In this paper, we prove that if we let $r=\text{ord} _{s=1}L(E, s)$, then under the assumption of the Riemann Hypothesis for $L(E, s)$, we have that $\prod \limits _{p \leq x} \frac{N_p}{p} \sim C (\log x)^r$ for all $x$ outside a set of finite logarithmic measure. As corollaries, we recover not only Goldfeld's result, but we also prove a result in the direction of the converse. Our method of proof is based on establishing the asymptotic behaviour of partial Euler products of $L(E, s)$ in the right-half of the critical strip.
