Geometric Function Theory and Applications―Festschrift for Grigore-Stefan Salagean's 75th Birthday

A special issue of Mathematics (ISSN 2227-7390). This special issue belongs to the section "Algebra, Geometry and Topology".

Deadline for manuscript submissions: 31 May 2025 | Viewed by 1623

Special Issue Editors


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Guest Editor
Department of Mathematics, Technical University of Cluj-Napoca, 400114 Cluj-Napoca, Romania
Interests: complex analysis; geometric function theory; special functions
Special Issues, Collections and Topics in MDPI journals

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Guest Editor
Department of Computing, Mathematics and Electronics, "1 Decembrie 1918" University of Alba Iulia, 510009 Alba Iulia, Romania
Interests: complex analysis; geometric function theory; integral operators
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleague,

This Special Issue is dedicated to Prof. Grigore-Stefan Salagean’s on the occasion of his 75th birthday.

Professor Salagean worked at Babes-Bolyai University, focusing on complex analysis. He has taught many doctoral and postdoctoral students.

Professor Salagean is one of the most distinguished professors in the field of complex variables. He has published books; monographs; edited volumes; book chapters; papers in international conference proceedings; and articles in various peer-reviewed international scientific research journals. He has also contributed forewords and prefaces to many books and journals.

The aim of this Special Issue is to bring together leading experts alongside young researchers studying topics related to univalent and geometric function theory and to present their recent research to the mathematical community.

This Special Issue, devoted to the topic of the “Geometric Function Theory and Applications”, will collate the latest research achievements of scholars studying the complex-valued functions of one or several variables.

Geometric function theory (GFT) is one of the most important branches of complex analysis. Its purpose is to relate the analytic properties of conformal maps to the geometric properties of their images, and it has many applications in various fields of mathematics, including special functions, dynamical systems, analytic number theory, fractional calculus, and probability distributions.

The purpose of this Special Issue is to bring together original research and review articles focusing on the latest developments in this research area and on applications of geometric function theory within other fields of research. Such articles not only provide new methods and results but may also have a great impact on the concept of symmetry.

Our goal is to promote and reinforce continued efforts to produce new results in these areas.

Topics that are invited for submission include (but are not limited to) the following:

  • Theory-differential and integral operators
  • Univalent and multivalent functions
  • Analysis of metric spaces
  • Spaces of analytic and meromorphic functions
  • Value distribution theory
  • Differential subordinations and superordinations
  • Applications of special functions in geometric function theory
  • Quasi-conformal mappings
  • Entire and meromorphic functions
  • Fuzzy differential subordinations and superordinations
  • Riemann surfaces
  • Generalized function theory
  • Bi-complex variable theory
  • Applications of quantum calculus in geometric function theory
  • Approximation theory
  • Universal functions
  • Harmonic univalent functions
  • Geometric function theory in several complex variables

Dr. Luminita-Ioana Cotirla
Prof. Dr. Valer-Daniel Breaz
Guest Editors

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Keywords

  • geometric function theory
  • complex analysis
  • special functions

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Published Papers (3 papers)

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Research

14 pages, 322 KiB  
Article
Coefficient Functionals of Sakaguchi-Type Starlike Functions Involving Caputo-Type Fractional Derivatives Subordinated to the Three-Leaf Function
by Kholood M. Alsager, Sheza M. El-Deeb, Gangadharan Murugusundaramoorthy and Daniel Breaz
Mathematics 2024, 12(14), 2273; https://doi.org/10.3390/math12142273 - 20 Jul 2024
Viewed by 421
Abstract
A challenging part of studying geometric function theory is figuring out the sharp boundaries for coefficient-related problems that crop up in the Taylor–Maclaurin series of univalent functions. Using Caputo-type fractional derivatives to define the families of Sakaguchi-type starlike functions with respect to symmetric [...] Read more.
A challenging part of studying geometric function theory is figuring out the sharp boundaries for coefficient-related problems that crop up in the Taylor–Maclaurin series of univalent functions. Using Caputo-type fractional derivatives to define the families of Sakaguchi-type starlike functions with respect to symmetric points, this article aims to investigate the first three initial coefficient estimates, the bounds for various problems such as Fekete–Szegő inequality, and the Zalcman inequalities, by subordinating to the function of the three leaves domain. Fekete–Szegő-type inequalities and initial coefficients for functions of the form H1 and ζH(ζ) and 12logHζζ connected to the three leaves functions are also discussed. Full article
15 pages, 309 KiB  
Article
Radii of γ-Spirallike of q-Special Functions
by Sercan Kazımoğlu
Mathematics 2024, 12(14), 2261; https://doi.org/10.3390/math12142261 - 19 Jul 2024
Viewed by 301
Abstract
The geometric properties of q-Bessel and q-Bessel-Struve functions are examined in this study. For each of them, three different normalizations are applied in such a way that the resulting functions are analytic in the unit disk of the complex plane. For [...] Read more.
The geometric properties of q-Bessel and q-Bessel-Struve functions are examined in this study. For each of them, three different normalizations are applied in such a way that the resulting functions are analytic in the unit disk of the complex plane. For these normalized functions, the radii of γ-spirallike and convex γ-spirallike of order σ are determined using their Hadamard factorization. These findings extend the known results for Bessel and Struve functions. The characterization of entire functions from the Laguerre-Pólya class plays an important role in our proofs. Additionally, the interlacing property of zeros of q-Bessel and q-Bessel-Struve functions and their derivatives is useful in the proof of our main theorems. Full article
19 pages, 310 KiB  
Article
Fractional Differential Operator Based on Quantum Calculus and Bi-Close-to-Convex Functions
by Zeya Jia, Alina Alb Lupaş, Haifa Bin Jebreen, Georgia Irina Oros, Teodor Bulboacă and Qazi Zahoor Ahmad
Mathematics 2024, 12(13), 2026; https://doi.org/10.3390/math12132026 - 29 Jun 2024
Viewed by 368
Abstract
In this article, we first consider the fractional q-differential operator and the λ,q-fractional differintegral operator Dqλ:AA. Using the λ,q-fractional differintegral operator, we define two new subclasses of analytic functions: [...] Read more.
In this article, we first consider the fractional q-differential operator and the λ,q-fractional differintegral operator Dqλ:AA. Using the λ,q-fractional differintegral operator, we define two new subclasses of analytic functions: the subclass S*q,β,λ of starlike functions of order β and the class CΣλ,qα of bi-close-to-convex functions of order β. We explore the results on coefficient inequality and Fekete–Szegö problems for functions belonging to the class S*q,β,λ. Using the Faber polynomial technique, we derive upper bounds for the nth coefficient of functions in the class of bi-close-to-convex functions of order β. We also investigate the erratic behavior of the initial coefficients in the class CΣλ,qα of bi-close-to-convex functions. Furthermore, we address some known problems to demonstrate the connection between our new work and existing research. Full article
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