Let
be a function
defined as the product of
and
, where
is a primitive
character. We determine the positivity and negativity properties of the real part of the logarithmic
derivative of
in the zero-free region. This result establishes an equivalence relation for the
generalized Riemann hypothesis. Furthermore, we prove that the modulus of
is
strictly increasing (respectively, decreasing) in the zero-free right (respectively, left)
half-plane along every circle centered at the intersection of the real axis and the
vertical boundary line of the zero-free right (respectively, left) half-plane.
Using this result, we propose a new criterion for the generalized Riemann
hypothesis.
Keywords
Riemann $\xi$-function, monotonicity, Riemann hypothesis,
Dirichlet character