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Joint discrete universality for $L$-functions from the Selberg class and periodic Hurwitz zeta-functions
A. Balčiūnasa, R. Macaitienėbc, D. Šiaučiūnasb a Vilnius University, Lithuania
b Research Institute,
Šiauliai University, Lithuania
c Šiauliai State College, Lithuania
Abstract:
The Selberg class $\mathcal{S}$ contains Dirichlet series
$$
\mathcal{L}(s)= \sum_{m=1}^\infty \frac{a(m)}{m^s}, \quad s=\sigma+it,
$$
such that, for every $\varepsilon>0$, $a(m)\ll_\varepsilon m^\varepsilon$; there exists an integer $k\geqslant 0$ such that $(s-1)^k \mathcal{L}(s)$ is an entire function of finite order; the functions $\mathcal{L}$ satisfy a functional equation connecting $s$ with $1-s$, and have a product representation over prime numbers. Steuding introduced a subclass $\widetilde{\mathcal{S}}$ of $\mathcal{S}$ with additional condition
$$
\lim_{x\to\infty} \left(\sum_{p\leqslant x} 1\right)^{-1} \sum_{p\leqslant x}|a(p)|^2=\kappa>0,
$$
where $p$ runs prime numbers.
Let $\alpha$, $0<\alpha\leqslant 1$, be a fixed parameter, and $\mathfrak{a}=\{a_m: m\in \mathbb{N}_0\}$ be a periodic sequence of complex numbers. The second object of the paper is the periodic Hurwitz zeta-function $\zeta(s,\alpha;\mathfrak{a})$ which is defined, for $\sigma>1$, by the Dirichlet series
$$
\zeta(s,\alpha; \mathfrak{a})=\sum_{m=0}^\infty \frac{a_m}{(m+\alpha)^s},
$$
and is meromorphically continued to the whole complex plane.
The paper is devoted to the discrete universality of the collection
$$
\left(\mathcal{L}(\widetilde{s}), \zeta(s,\alpha_1; \mathfrak{a}_{11}), \dots,\zeta(s,\alpha_1; \mathfrak{a}_{1l_1}), \dots, \zeta(s,\alpha_r; \mathfrak{a}_{r1}), \dots, \zeta(s,\alpha_r; \mathfrak{a}_{rl_r})\right),
$$
where $\mathcal{L}(\widetilde{s})\in \widetilde{S}$, and $\zeta(s,\alpha_j; \mathfrak{a}_{jl_j})$ are periodic Hurwitz zeta-functions, i. e., to the simultaneous approximation of a collection
$$
\left(f(\widetilde{s}), f_{11}(s),\dots, f_{1l_1}(s), \dots, f_{r1}(s), \dots, f_{rl_r}(s)\right)
$$
of analytic functions from a wide class by a collection of shifts
\begin{align*}
\big(\mathcal{L}(\widetilde{s}+ikh), &\zeta(s+ikh_1,\alpha_1; \mathfrak{a}_{11}), \dots,\zeta(s+ikh_1,\alpha_1; \mathfrak{a}_{1l_1}), \dots, \\ &
\zeta(s+ikh_r,\alpha_r; \mathfrak{a}_{r1}), \dots, \zeta(s+ikh_r,\alpha_r; \mathfrak{a}_{rl_r})\big),
\end{align*}
where $h, h_1, \dots, h_r$ are positive numbers, is considered. For this, the linear independence over the field of rational numbers for the set
$$
\left\{\left(h\log p: p\in \mathbb{P}\right), \left( h_j\log(m+\alpha_j): m\in \mathbb{N}_0,\, j=1,\dots, r\right), 2\pi\right\},
$$
where $\mathbb{P}$ denotes the set of all prime numbers, is applied.
Keywords:
Dirichlet series, Hurwitz zeta-function, periodic Hurwitz zeta-function, Selberg class, universality, weak convergence.
Received: 09.01.2019 Accepted: 10.04.2019
Citation:
A. Balčiūnas, R. Macaitienė, D. Šiaučiūnas, “Joint discrete universality for $L$-functions from the Selberg class and periodic Hurwitz zeta-functions”, Chebyshevskii Sb., 20:1 (2019), 46–65
Linking options:
https://www.mathnet.ru/eng/cheb717 https://www.mathnet.ru/eng/cheb/v20/i1/p46
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Abstract page: | 103 | Full-text PDF : | 20 | References: | 18 |
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