Abstract:
Let $r = m(\rho)$ denote the multiplicity of the complex
zero $\rho = \beta + i\gamma$ of the Riemann zeta-function $\zeta(s)$. The present work,
which is a continuation of [1], brings forth several results involving $m(\rho)$.
It is seen that the problem can be reduced to the estimation of integrals of the zeta-function
over “very short” intervals. This is related to the “Karatsuba conjectures” (see [2]),
related to the quantity
$$
F(T,\Delta)\,:=\,\max_{t\in[T,\, T+\Delta]} |\zeta({\textstyle\frac12}+it)|
\qquad 0 < \Delta\,=\,\Delta(T) \le 1.
$$
By the complex integration technique, a new, explicit bound for
$m(\beta+i\gamma)$ is also derived, which is relevant when $\beta$ is close to unity. As a corollary, it follows that, for
$\tfrac{5}{6}\le\beta < 1$ and $\gamma\ge\gamma_1$, we have
$$
m(\beta+i\gamma)\,\le\,4\log\log\gamma + 20(1-\beta)^{3/2}\log \gamma.
$$
[1] A. Ivić, On the multiplicity of zeros of the zeta-function.
Bulletin CXVIII de l'Académie Serbe des Sciences et des Arts – 1999,
Classe des Sciences mathématiques et naturelles,
Sciences mathématiques. №. 24. P. 119–131.
[2] A.A. Karatsuba, On lower bounds for the Riemann zeta-function. Dokl. Math. 63:1 (2001). P. 9 – 10
(translation from: Dokl. Akad. Nauk. 376:1 (2001). P. 15 – 16).