The quasi-Riemann hypothesis asserts that the Riemann zeta function has a fixed zero-free half-plane
for some real number
. Thus one constant
must work at every height
, unlike classical zero-free
regions whose boundaries approach
. The pole at
is not a zero and is excluded when stating nonvanishing.
The Riemann hypothesis implies this assertion
with
,
but the quasi-Riemann hypothesis does not require that value (Davenport 1980, Billington
et al. 2025).
A stronger uniform version asks for the same for all Dirichlet
L-series, independently of the number
theoretic character, its modulus, and the height. The generalized
Riemann hypothesis would give
in this version as well.