Slightly improved zero-free half-planes for the quasi-Riemann hypothesis

Abstract: Recently, a uniform $\frac{7}{8}$ zero-free half-plane for finite-order Hecke $L$-functions over $\mathbb Q(\sqrt{-3})$ and its transfer to Dirichlet $L$-functions was given by OpenAI in [1]. In its proof, there are two chosen parameters $b=\frac{1}{8}, \ell=\frac{1}{6}$. In this note, via varying $b$ and $\ell$, following the same strategy, we slightly improve the bound $\frac{7}{8}=0.875$ to be $$B_{\mathrm r}=\frac{34999}{40000}=0.874975, (\text{when }b_{\mathrm r}=\frac{1}{8}, \ell_{\mathrm r}=\frac{1}{6} + \frac{1}{10000});$$ and [ \begin{gathered} B_{\mathrm{new}}=\frac{1507-2\sqrt{921}}{1653} =0.874957069799\ldots, (\text{when }b_{\mathrm{new}}=-\frac{4}{29}+\frac{230\sqrt{921}}{26709}, \ell_{\mathrm{new}}=\frac{33+8\sqrt{921}}{1653}). \end{gathered} ] This result has been formalized by Lean ([15]).