Vanishing, Unbounded and Angular Shifts on the Quotient of the Difference and the Derivative of a Meromorphic Function

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Main Authors: Asikainen, Lasse, Chen, Yu, Korhonen, Risto
Format: Preprint
Published: 2025
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author Asikainen, Lasse
Chen, Yu
Korhonen, Risto
author_facet Asikainen, Lasse
Chen, Yu
Korhonen, Risto
contents We show that for a vanishing period difference operator of a meromorphic function \( f \), there exist the following estimates regarding proximity functions, \[ \lim_{η\to 0} m_η\left(r, \frac{Δ_ηf - aη}{f' - a} \right) = 0 \] and \[ \lim_{r \to \infty} m_η\left(r, \frac{Δ_ηf - aη}{f' - a} \right) = 0, \] where \( Δ_ηf = f(z + η) - f(z) \), and \( |η| \) is less than an arbitrarily small quantity \( α(r) \) in the second limit. Then, under certain assumptions on the growth, restrictions on the period tending to infinity, and on the value distribution of a meromorphic function \( f(z) \), we have \[ m\left(r, \frac{Δ_ωf - aω}{f' - a} \right) = S(r, f'), \] as \( r \to \infty \), outside an exceptional set of finite logarithmic measure. Additionally, we provide an estimate for the angular shift under certain conditions on the shift and the growth. That is, the following Nevanlinna proximity function satisfies \[ m\left(r, \frac{f(e^{iω(r)}z) - f(z)}{f'} \right) = S(r, f), \] outside an exceptional set of finite logarithmic measure. Furthermore, the above estimates yield additional applications, including deficiency relations between \( Δ_ηf \) (or \( Δ_ωf \)) and \( f' \), as well as connections between \( η/ω\)-separated pair indices and \( δ(0, f') \).
format Preprint
id arxiv_https___arxiv_org_abs_2505_21150
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Vanishing, Unbounded and Angular Shifts on the Quotient of the Difference and the Derivative of a Meromorphic Function
Asikainen, Lasse
Chen, Yu
Korhonen, Risto
Complex Variables
30D35
We show that for a vanishing period difference operator of a meromorphic function \( f \), there exist the following estimates regarding proximity functions, \[ \lim_{η\to 0} m_η\left(r, \frac{Δ_ηf - aη}{f' - a} \right) = 0 \] and \[ \lim_{r \to \infty} m_η\left(r, \frac{Δ_ηf - aη}{f' - a} \right) = 0, \] where \( Δ_ηf = f(z + η) - f(z) \), and \( |η| \) is less than an arbitrarily small quantity \( α(r) \) in the second limit. Then, under certain assumptions on the growth, restrictions on the period tending to infinity, and on the value distribution of a meromorphic function \( f(z) \), we have \[ m\left(r, \frac{Δ_ωf - aω}{f' - a} \right) = S(r, f'), \] as \( r \to \infty \), outside an exceptional set of finite logarithmic measure. Additionally, we provide an estimate for the angular shift under certain conditions on the shift and the growth. That is, the following Nevanlinna proximity function satisfies \[ m\left(r, \frac{f(e^{iω(r)}z) - f(z)}{f'} \right) = S(r, f), \] outside an exceptional set of finite logarithmic measure. Furthermore, the above estimates yield additional applications, including deficiency relations between \( Δ_ηf \) (or \( Δ_ωf \)) and \( f' \), as well as connections between \( η/ω\)-separated pair indices and \( δ(0, f') \).
title Vanishing, Unbounded and Angular Shifts on the Quotient of the Difference and the Derivative of a Meromorphic Function
topic Complex Variables
30D35
url https://arxiv.org/abs/2505.21150