Classical zero-free region constant

Description of constant

$C_{8} = R$ is the least constant such that there are no zeroes $\sigma+it$ of the Riemann zeta function with $\lvert t \rvert \geq 2$ and $\sigma > 1 - \frac{1}{R \log \lvert t \rvert}$.

Known upper bounds

Bound Reference Comments
$0$ Trivial  
$34.82$ [dlVP1899] Implies the prime number theorem
$19$ [RS1962]  
$9.64591$ [S1970]  
$8.463$ [F2002]  
$5.69693$ [K2005]  
$5.68371$ [JK2014]  
$5.5666305$ [MT2014]  
$5.558691$ [MTY2022]  

Known lower bounds

Bound Reference Comments
$2/\log \gamma_{1} \approx 0.755106$ - Optimal assuming RH

References