In 2003, Garunkštis provided a lower bound for the lower density of the universality theorem for the Riemann zeta-function. In this paper, we generalize this result for the hybrid joint universality theorem for Dirichlet $L$-functions whose moduli are prime numbers. Furthermore, by its application, we estimate a lower bound of the lower density of the universality theorem for Hurwitz zeta-functions with rational parameters.
We prove that the Dirichlet $L$-functions associated with Dirichlet characters in $\mathbb{F}_{q}[x]$ are universal. That is, given a modulus of high enough degree, $L$-functions with characters to this modulus can be found that approximate any given nonvanishing analytic function arbitrarily closely.
In the paper we introduce the new approach how to use an orthonormality relation of coefficients of Dirichlet series defining given L-functions from the Selberg class to prove joint universality.
Two remarks related with the mixed joint universality for a polynomial Euler product and a periodic Hurwitz zeta-function with a transcendental parameter are given. One is the mixed joint functional independence, and the other is a generalized universality, which includes several periodic Hurwitz zeta-functions.
We prove joint universality theorems on the half plane of absolute convergence for general classes of Dirichlet series with an Euler-product, where in addition to vertical shifts we also allow scaling. This generalizes our recent joint universality results for Dirichlet $L$-functions. In contrast to classical universality, we do not need that the Dirichlet series in question have an analytic continuation beyond their region of absolute convergence. Also we may allow weaker orthogonality conditions for pairs of Dirichlet series than in the previous joint universality results of Lee-Nakamura-Pań…
We give a new type of mixed discrete joint universality properties, which is satisfied by a wide class of zeta-functions. We study the universality for a certain modification of a Matsumoto zeta-function and a periodic Hurwitz zeta-function under certain arithmetic condition on the common difference of arithmetical progression and the shifting parameter. Also we generalize a known discrete universality result in our former paper and the new one as well.
We present the most general at this moment results on the discrete mixed joint value-distribution and the universality property for the class of Matsumoto zeta-functions and periodic Hurwitz zeta-functions under certain linear independence condition on the relevant parameters, such as common differences of arithmetic progressions, prime numbers etc.
For $0<α, λ\leq 1$, the Lerch zeta-function is defined by $L(s;α, λ)$$:= \sum_{n=0}^\infty e^{2πiλn} (n+α)^{-s}$, where $σ>1$. In this paper, we prove joint universality for Lerch zeta-functions with distinct $λ_1,\ldots,λ_m$ and transcendental $α$.
Joint extreme values of Dirichlet (L)-functions and their logarithmic derivatives
School of Mathematical Sciences, Key Laboratory of Intelligent Computing and Applications(Ministry of Education), Tongji University（同济大学数学科学学院，智能计算与应用教育部重点实验室）
We study analytic properties of the pair consisting of a rather general form of zeta-function with an Euler product and a periodic Hurwitz zeta-function with a transcendental parameter. We first survey briefly previous results, and then investigate the mixed joint discrete value distribution and prove the mixed joint discrete universality theorem for these functions, in the case when common differences of relevant arithmetic progressions are not necessarily the same. Also some generalizations are given. For this purpose, certain arithmetic conditions on the common differences are necessary.
We prove a mixed joint discrete universality theorem for a Matsumoto zeta-function $φ(s)$ (belonging to the Steuding subclass) and a periodic Hurwitz zeta-function $ζ(s,α;{\mathfrak{B}})$. For this purpose, certain independence condition for the parameter $α$ and the minimal step of discrete shifts of these functions is assumed. This paper is a continuation of authors' works [12] and [arXiv:1601.03795].
We prove a new case of mixed discrete joint universality theorem on approximation of certain target couple of analytic functions by the shifts of a pair consisting of the function belonging to wide class of Matsumoto zeta-functions and the periodic Hurwitz zeta-function. We work under the condition that the common difference of arithmetical progression satisfies a certain rational condition and the parameter is a transcendental number. The essential difference from the result in our previous article is that here we do not study the class of partial zeta-functions, but work with the class of th…
The property of zeta-functions on mixed joint universality in the Voronin's sense states that any two holomorphic functions can be approximated simultaneously with accuracy $ε>0$ by suitable vertical shifts of the pair consisting from the Riemann zeta- and Hurwitz zeta-functions. In [1], it was shown rather general result, i.e., an approximating pair was composed of the Matsumoto zeta-functions' class and the periodic Hurwitz zeta-function. In this paper, we prove that this set of shifts has a strict positive density for all but at most countably many $ε>0$. Also, we give the concluding remark…
We prove that, for every rational $d\ne 0,\pm 1$ and every compact set $K\subset\{s\in\mathbb{C}:1/2<\Re(s)<1\}$ with connected complement, any analytic non-vanishing functions $f_1,f_2$ on $K$ can be approximated, uniformly on $K$, by the shifts $ζ(s+iτ)$ and $ζ(s+idτ)$, respectively. As a consequence we deduce that the set of $τ$ satisfying $|ζ(s+iτ)-ζ(s+idτ)|<\varepsilon$ uniformly on $K$ has a positive lower density for every $d\ne 0$.
We use subsequence and moving average ergodic theorems applied to Boole's transformation and its variants and their invariant measures on the real line to give new characterisations of the Lindelh{ö}f Hypothesis and the Riemann hypothesis. These ideas are then used to study the value distribution of Dirichlet L series, and the zeta functions of Dedekind, Hurwitz and Riemann and their derivatives. This builds on earlier work of R. L. using Birkhoff's ergodic theorem and probability theory.
We prove that, for arbitrary Dirichlet $L$-functions $L(s;χ_1),\ldots,L(s;χ_n)$ (including the case when $χ_j$ is equivalent to $χ_l$ for $j\ne k$), suitable shifts of type $L(s+iα_jt^{a_j}\log^{b_j}t;χ_j)$ can simultaneously approximate any given analytic functions on a simply connected compact subset of the right open half of the critical strip, provided the pairs $(a_j,b_j)$ are distinct and satisfy certain conditions. Moreover, we consider a discrete analogue of this problem where $t$ runs over the set of positive integers.
The class of Dirichlet series associated with a periodic arithmetical function $f$ includes the Riemann zeta-function as well as Dirichlet $L$-functions to residue class characters. We study the value-distribution of these Dirichlet series $L(s;f)$, resp. their analytic continuation in the neighborhood of the critical line (which is the abscissa of symmetry of the related Riemann-type functional equation). In particular, for a fixed complex number $a\neq 0$, we prove for an even or odd periodic $f$ the number of $a$-points of the $Δ$-factor of the functional equation, prove the existence of th…
We prove effective results on when a function can be approximated by a Dirichlet polynomial with bounded coefficients. Assuming that Φ(n) is an increasing function we prove that the set of polynomials {\sum_{n=2}^N a_n n^{it-1}: N \geq 2, |a_n| \leq Φ(n)}, is dense in L^2(0,H) if and only if \sum_{n=2}^\infty \frac{\log Φ(n)} {n \log^2 n} = \infty. We also prove variants of this result for generalized Dirichlet polynomials. The main tools are theorems of Paley and Wiener related to quasianalyticity and the Pechersky rearrangement theorem. We use this result to give precise conditions on when a…
We study universality properties of the Epstein zeta function $E_n(L,s)$ for lattices $L$ of large dimension $n$ and suitable regions of complex numbers $s$. Our main result is that, as $n\to\infty$, $E_n(L,s)$ is universal in the right half of the critical strip as $L$ varies over all $n$-dimensional lattices $L$. The proof uses an approximation result for Dirichlet polynomials together with a recent result on the distribution of lengths of lattice vectors in a random lattice of large dimension and a strong uniform estimate for the error term in the generalized circle problem. Using the same …
We study the value-distribution of the Riemann zeta-function and related functions on and near the critical line. Amongst others, we focus on the following: The critical line is a natural boundary of the Voronin-type universality property of the Riemann zeta-function. We study a modified concept of `universality' at the critical line: roughly speaking, we add a scaling factor to the vertical shifts that appear in Voronin's universality theorem. Levinson showed that almost all a-points of the Riemann zeta-function lie in a certain funnel-shaped region around the critical line. We rely on argume…
We prove, assuming the Riemann Hypothesis, that \int_{T}^{2T} |ζ(1/2+it)|^{2k} dt \ll_{k} T log^{k^{2}} T for any fixed k \geq 0 and all large T. This is sharp up to the value of the implicit constant. Our proof builds on well known work of Soundararajan, who showed, assuming the Riemann Hypothesis, that \int_{T}^{2T} |ζ(1/2+it)|^{2k} dt \ll_{k,ε} T log^{k^{2}+ε} T for any fixed k \geq 0 and ε> 0. Whereas Soundararajan bounded \log|ζ(1/2+it)| by a single Dirichlet polynomial, and investigated how often it attains large values, we bound \log|ζ(1/2+it)| by a sum of many Dirichlet polynomials and…
This paper studies zeta functions of the form $\sum_{n=1}^{\infty} χ(n) n^{-s}$, with $χ$ a completely multiplicative function taking only unimodular values. We denote by $σ(χ)$ the infimum of those $α$ such that the Dirichlet series $\sum_{n=1}^{\infty} χ(n) n^{-s}$ can be continued meromorphically to the half-plane $\operatorname{Re} s>α$, and denote by $ζ_χ(s)$ the corresponding meromorphic function in $\operatorname{Re} s>σ(χ)$. We construct $ζ_χ(s)$ that have $σ(χ)\le 1/2$ and are universal for zero-free analytic functions on the half-critical strip $1/2<\operatorname{Re} s <1$, with zero…
