Joint universality for dependent $L$-functions

TL;DR

This paper establishes joint universality results for dependent Dirichlet L-functions, showing they can simultaneously approximate arbitrary analytic functions under specific shifts, including a discrete version over positive integers.

Contribution

It extends universality theorems to dependent L-functions with shifts involving powers and logs, including a discrete analogue, broadening the scope of universality results.

Findings

Simultaneous approximation of analytic functions by shifted dependent L-functions.

Conditions on shifts ensure universality holds for various L-functions.

Discrete analogue over positive integers demonstrated.

Abstract

We prove that, for arbitrary Dirichlet $L$-functions $L(s;\chi_1),\ldots,L(s;\chi_n)$ (including the case when $\chi_j$ is equivalent to $\chi_l$ for $j\ne k$), suitable shifts of type $L(s+i\alpha_jt^{a_j}\log^{b_j}t;\chi_j)$ 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.