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Related papers: A Conjecture on $H_3(1)$ For Certain Starlike Func…

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In 2011, Sok\'{o}{\l} (Comput. Math. Appl. 62, 611--619) introduced and studied the class $\mathcal{SK}(\alpha)$ as a certain subclass of starlike functions, consists of all functions $f$ ($f(0)=0=f'(0)-1$) which satisfy in the following…

Complex Variables · Mathematics 2018-04-19 R. Kargar , H. Mahzoon , N. Kanzi

Marx and Strohh\"acker showed around in 1933 that $f(z)/z$ is subordinate to $1/(1-z)$ for a normalized convex function $f$ on the unit disk $|z|<1.$ Brickman, Hallenbeck, MacGregor and Wilken proved in 1973 further that $f(z)/z$ is…

Complex Variables · Mathematics 2015-02-19 Toshiyuki Sugawa , Li-Mei Wang

For the classes of analytic functions $f$ defined on the unit disk satisfying $$\frac{z {f}'(z)}{f(z) - f(-z)} \prec \varphi(z) \quad \text{and} \quad \frac{(2 z {f}'(z))'}{(f(z) - f(-z))'} \prec \varphi(z),$$ denoted by…

Complex Variables · Mathematics 2022-10-25 Surya Giri , S. Sivaprasad Kumar

In this study, we deal with the sharp bounds of certain Toeplitz determinants whose entries are the logarithmic coefficients of analytic univalent functions $f$ such that the quantity $z f'(z)/f(z)$ takes values in a specific domain lying…

Complex Variables · Mathematics 2023-03-28 Surya Giri , S. Sivaprasad Kumar

In the present investigation, we study the class of Sigmoid starlike functions, given by $\mathcal{S}^*_{SG}=\{f\in\mathcal{A}: {zf'(z)}/{f(z)}\prec 2/(1+e^{-z})\}$ in context of estimating the sharp radius constants associated with several…

Complex Variables · Mathematics 2022-08-03 Priyanka Goel , S. Sivaprasad Kumar

This paper establishes sharp bounds for the second and third-order Toeplitz determinants associated with starlike functions $f$ in the unit disk such that $f(z)-z$ has a zero of order $k+1$ at $z=0$. These bounds are further extended to…

Complex Variables · Mathematics 2026-01-07 Surya Giri , S. Sivaprasad Kumar

Let $f$ and $g$ be analytic functions on the open unit disk of the complex plane with $f/g$ belonging to the class $\mathcal{P} $ of functions with positive real part consisting of functions $p$ with $p(0)=1$ and $\operatorname{Re} p(z)>0$…

Complex Variables · Mathematics 2020-06-23 Ahmad Sulaiman Ahmad El-Faqeer , Maisarah Haji Mohd , V. Ravichandran , Shamani Supramaniam

It is crucial to explore the sharp bounds of logarithmic coefficients and the Hankel determinant involving logarithmic coefficients as part of coefficient problems in various function classes. Our primary objective in this study is to…

Complex Variables · Mathematics 2025-02-06 Sanju Mandal , Molla Basir Ahamed

In the past several subclasses of starlike functions are defined involving real part and modulus of certain expressions of functions under study, combined by way of an inequality. In the similar fashion, we introduce a new class…

Complex Variables · Mathematics 2021-08-25 S. Sivaprasad Kumar , Shagun Banga

Recent advances in image and signal processing have drawn on geometric function theory, particularly coefficient estimate problems. Motivated by their significance, we introduce a class of starlike functions related to a balloon-shaped…

Complex Variables · Mathematics 2026-02-19 S. Sivaprasad Kumar , A. Tripathi

We determine sharp bounds on some Hankel determinants involving initial coefficients, inverse coefficients, and logarithmic inverse coefficients for two subclasses of Sakaguchi functions which are associated with the right half of the…

Complex Variables · Mathematics 2023-08-23 Sushil Kumar , Rakesh Kumar Pandey , Pratima Rai

A starlike univalent function $f$ is characterized by the function $zf'(z)/f(z)$; several subclasses of these functions were studied in the past by restricting the function $zf'(z)/f(z)$ to take values in a region $\Omega$ on the right-half…

Complex Variables · Mathematics 2021-01-06 Shalu Yadav , Kanika Sharma , V. Ravichandran

In 1984, Clunie and Sheil-Small proved that a sense-preserving harmonic function whose analytic part is convex, is univalent and close-to-convex. In this paper, certain cases are discussed under which the conclusion of this result can be…

Complex Variables · Mathematics 2013-11-12 Sumit Nagpal , V. Ravichandran

This paper aims to pursue some classes of normalized analytic functions $f$ with fixed second coefficient defined on open unit disk, such that ${(1+z)^2f(z)}/{z}$ and ${(1+z)f(z)}/{z}$ are functions having positive real part. The radius of…

Complex Variables · Mathematics 2022-03-17 Sushil Kumar , Swati Anand , Naveen Kumar Jain

For an analytic function f(z)=z+\sum_{n=2}^\infty a_n z^n satisfying the inequality \sum_{n=2}^\infty n(n-1)|a_n|\leq \beta, sharp bound on $\beta$ is determined so that $f$ is either starlike or convex of order $\alpha$. Several other…

Complex Variables · Mathematics 2012-08-02 Rosihan M. Ali , Moradi Nargesi Mahnaz , V. Ravichandran

For $-1\leq B<A\leq 1$, let $\mathcal{S}^*(A,B)$ denote the class of Janowski starlike functions which satisfy the subordination relation $zf'(z)/f(z)\prec (1+Az)/(1+Bz)$. In the present article, we determine the sharp of pre-Schwarzian…

Complex Variables · Mathematics 2021-11-22 Md Firoz Ali , Sanjit Pal

For $f\in \mathcal{S}$, the class of normalized functions, analytic and univalent in the unit disk $\mathbb{D}$ and given by $f(z)=z+\sum_{n=2}^{\infty} a_n z^n$ for $z\in \mathbb{D}$, we give an upper bound for the coefficient difference…

Complex Variables · Mathematics 2021-11-22 Milutin Obradovic , Derek K. Thomas , Nikola Tuneski

This paper presents several results concerning second and third-order differential subordination for the class $\mathcal{S}^{*}_{e}:=\{f\in \mathcal{A}:zf'(z)/f(z)\prec e^z\}$, which represents the class of starlike functions associated…

Complex Variables · Mathematics 2024-01-09 Neha Verma , S. Sivaprasad Kumar

We consider three classes of functions defined using the class $\mathcal{P}$ of all analytic functions $p(z)=1+cz+\dotsb$ on the open unit disk having positive real part and study several radius problems for these classes. The first class…

Complex Variables · Mathematics 2020-07-21 Adam Lecko , V. Ravichandran , Asha Sebastian

In the present investigation, we introduce a new subclass of starlike functions defined by $\mathcal{S}^{*}_{\tau}:=\{f\in \mathcal{A}:zf'(z)/f(z) \prec 1+\arctan z=:\tau(z)\}$, where $\tau(z)$ maps the unit disk $\mathbb {D}:= \{z\in…

Complex Variables · Mathematics 2023-12-27 S. Sivaprasad Kumar , Neha Verma