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TÜBİTAK

Turkish Journal of Mathematics

2019

Starlike functions

Articles 1 - 3 of 3

Full-Text Articles in Physical Sciences and Mathematics

A New Comprehensive Subclass Of Analytic Bi-Close-To-Convex Functions, Serap Bulut Jan 2019

A New Comprehensive Subclass Of Analytic Bi-Close-To-Convex Functions, Serap Bulut

Turkish Journal of Mathematics

In a very recent work, Şeker and Sümer Eker [On subclasses of bi-close-to-convex functions related to the odd-starlike functions. Palestine Journal of Mathematics 2017; 6: 215-221] defined two subclasses of analytic bi-close-to-convex functions related to the odd-starlike functions in the open unit disk $\mathbb{U}$. The main purpose of this paper is to generalize and improve the results of Şeker and Sümer Eker (in the aforementioned study) defining a comprehensive subclass of bi-close-to-convex functions. Also, we investigate the Fekete-Szegö type coefficient bounds for functions belonging to this new class.


Subclasses Of Uniformly Convex And Starlike Functions Associated Withbessel Functions, Muhammad Naeem, Saqib Hussain, Fethi̇ye Müge Sakar, Tahir Mahmood, Akhter Rasheed Jan 2019

Subclasses Of Uniformly Convex And Starlike Functions Associated Withbessel Functions, Muhammad Naeem, Saqib Hussain, Fethi̇ye Müge Sakar, Tahir Mahmood, Akhter Rasheed

Turkish Journal of Mathematics

In recent years, applications of Bessel differential equations have been commonly used in univalent functions theory. The main object of the present paper is to give some characteristic properties for some subclasses of uniformly starlike and convex functions which are defined here by means of the normalized form of the generalized Bessel function to be univalent in the open unit disc. Furthermore, we also establish some results of these subclasses related to a particular integral operator. Some corresponding consequences of our main results are also considered.


Some Properties For A Class Of Analytic Functions Defined By A Higher-Order Differential Inequality, Oqlah Alrefai Jan 2019

Some Properties For A Class Of Analytic Functions Defined By A Higher-Order Differential Inequality, Oqlah Alrefai

Turkish Journal of Mathematics

Let $\mathcal{B}_p(\alpha,\beta, \lambda;j)$ be the class consisting of functions $f(z)= z^p+\sum_{k=p+1}^{\infty}a_k z^{k},\; p\in \mathbb{N}$ which satisfy $ \mathrm{Re}\left\{\alpha\frac{f^{(j)}(z)}{z^{p-j}}+\beta\frac{f^{(j+1)}(z)}{z^{p-j-1}}+\left(\frac{\beta-\alpha}{2}\right)\frac{f^{(j+2)}(z)}{z^{p-j-2}}\right\}>\lambda,\;\;(z\in \mathbb{U}=\{z:\; z (5-12\ln 2)/(44-48\ln 2)\approx -0.309$ is sufficient condition for any normalized analytic function $f$ to be starlike in $\mathbb{U}$. The results improve and include a number of known results as their special cases.