Turkish Journal of Science
Journal license

Journal

Turkish Journal of Science


Volume
& Issue

Volume 11, Issue 1


Published
on

February 26, 2026


Pages

12-21


DOI

Article

Hankel and Hermitian–Toeplitz Determinants for Einstein-Type Sakaguchi Functions

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Authors

Erhan Deniz Affiliation:
Department of Mathematics, Faculty of Science and Letters, Kafkas University, Kars, Tu¨rkiye
and Elif Aysegul Cin Affiliation:
Department of Mathematics, Faculty of Science and Letters, Kafkas University, Kars, Tu¨rkiye


Abstract

In this paper, we introduce and investigate two Sakaguchi-type subclasses of normalized analytic functions which are generated by subordination to the Einstein function

\[
E(z) = \frac{z}{e^{z} - 1}.
\]

The first class is defined through the Sakaguchi starlikeness expression, whereas the second one is obtained from the corresponding Sakaguchi convexity expression; accordingly, these classes are denoted by \(S_E^{*}\) and \(C_E\), respectively. For functions

\[
f(z) = z + \sum_{n=2}^{\infty} a_n z^{n}
\]

belonging to these classes, we determine bounds for the first three non-trivial Taylor coefficients and then use these coefficient relations to estimate the second-order Hankel determinants \(H_{2,1}(f)\) and \(H_{2,2}(f)\). We also obtain two-sided estimates for the Hermitian–Toeplitz determinants \(T_{2,1}(f)\) and \(T_{3,1}(f)\). The analysis is based on the Schwarz-function representation of subordination, coefficient comparison with the Einstein expansion, and the classical Carathéodory coefficient parametrization, which enables the relevant determinant functionals to be reduced to explicitly tractable functions of two real parameters.


Keywords

Analytic functions, univalent functions, Sakaguchi functions, Einstein function, Hankel determinant.


Citation

Deniz, E. & Cin, E. A. (2026). Hankel and hermitian–toeplitz determinants for einstein-type sakaguchi functions. Turkish Journal of Science, 11(1), 12–21. https://doi.org/10.66833/TJOS-2026-0002

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