A1 Refereed original research article in a scientific journal
On a certain subclass of strongly starlike functions
Authors: Kargar, Rahim; Sokół, Janusz; Mahzoon, Hesam
Publisher: Springer Nature
Publication year: 2026
Journal: Analysis and Mathematical Physics
Article number: 37
Volume: 16
ISSN: 1664-2368
eISSN: 1664-235X
DOI: https://doi.org/10.1007/s13324-026-01188-5
Publication's open availability at the time of reporting: Open Access
Publication channel's open availability : Partially Open Access publication channel
Web address : https://doi.org/10.1007/s13324-026-01188-5
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/523417371
Self-archived copy's licence: CC BY
Self-archived copy's version: Publisher`s PDF
Let S*(α1, α2), where α1, α2 ∈ (0, 1], represent the class of functions f that are analytic in the open unit disk D, normalized by f (0) = f ' (0) − 1 = 0, and satisfying the following double-sided inequality:
−πα1 / 2 < arg {zf ' (z) / f (z)} < πα2 / 2 , (z ∈ D).
In this manuscript, we estimate the coefficients and logarithmic coefficients associated with functions that belong to the class S*(α1, α2). As a result, we provide a general bound for the coefficients of a strongly starlike function, which has been an open question until now. Finally, we derive upper and lower bounds for the expression Re{zf '(z) / f (z)}, where f ∈ S*(α1, α2).
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Funding information in the publication:
Open Access funding provided by University of Turku (including Turku University Central Hospital).
