Published online by Cambridge University Press: 03 April 2018
Let $L(s,\unicode[STIX]{x1D712})$ be the Dirichlet
$L$-function associated to a non-principal primitive character
$\unicode[STIX]{x1D712}$ modulo
$q$ with
$3\leqslant q\leqslant 400\,000$. We prove a new explicit zero-free region for
$L(s,\unicode[STIX]{x1D712})$:
$L(s,\unicode[STIX]{x1D712})$ does not vanish in the region
$\mathfrak{Re}\,s\geqslant 1-1/(R\log (q\max (1,|\mathfrak{Im}\,s|)))$ with
$R=5.60$. This improves a result of McCurley where
$9.65$ was shown to be an admissible value for
$R$.