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Some of important univalence criteria for a non-constant meromorphic function $f(z)$ on the unit disk $\ID$ involve its pre-Schwarzian or Schwarzian derivative. We consider an appropriate norm for the pre-Schwarzian derivative, and discuss…

Complex Variables · Mathematics 2012-03-20 S. Ponnusamy , S. K. Sahoo , T. Sugawa

Consider the family of locally univalent analytic functions $h$ in the unit disk $|z|<1$ with the normalization $h(0)=0$, $h'(0)=1$ and satisfying the condition $${\real} \left( \frac{z h''(z)}{\alpha h'(z)}\right) <\frac{1}{2} ~\mbox{ for…

Complex Variables · Mathematics 2024-07-23 Liulan Li , Saminthan Ponnusamy

In the paper, we use the idea of normal family to find out the possible solution of the following special case of algebraic differential equation \[P_k\big(z,f,f^{(1)},\ldots, f^{(k)}\big)=f^{(1)}(f-\mathscr{L}_k(f))-\varphi (f-a)(f-b)=0,\]…

Complex Variables · Mathematics 2025-09-15 Junfeng Xu , Sujoy Majumder , Nabadwip Sarkar , Lata Mahato

Let F be a family of holomorphic functions and let K be a constant less than 4. Suppose that for all f in F the second iterate of f does not have fixed points for which the modulus of the multiplier is greater than K. We show that then F is…

Complex Variables · Mathematics 2010-04-02 Walter Bergweiler

We show that the family of all holomorphic functions $f$ in a domain $D$ satisfying $$\frac{|f^{(k)}|}{1+|f|}(z)\le C \qquad \mbox{ for all } z\in D$$ (where $k$ is a natural number and $C>0$) is quasi-normal. Furthermore, we give a general…

Complex Variables · Mathematics 2016-09-21 Jürgen Grahl , Tomer Manket , Shahar Nevo

In this paper, we prove normality criteria for families of meromorphic functions involving sharing of a holomorphic function by a certain class of differential polynomials. Results in this paper extends the works of different authors…

Complex Variables · Mathematics 2015-04-01 Virender Singh , Kuldeep Singh Charak

Let $\ID$ denote the open unit disk and $f:\,\ID\TO\BAR\IC$ be meromorphic and univalent in $\ID$ with the simple pole at $p\in (0,1)$ and satisfying the standard normalization $f(0)=f'(0)-1=0$. Also, let $f$ have the expansion…

Complex Variables · Mathematics 2010-08-31 Bappaditya Bhowmik , Saminathan Ponnusamy

In this paper, we study the concepts of normal functions and $\varphi$-normal functions in the framework of planar harmonic mappings. We establish the harmonic mapping counterpart of the well-known Zalcman-Pang lemma and as a consequence,…

Complex Variables · Mathematics 2025-06-24 Nikhil Bharti , Nguyen Van Thin

We prove that the family $\mathcal{F}_C(D)$ of all meromorphic functions $f$ on a domain $D\subseteq \mathbb{C}$ with the property that the spherical area of the image domain $f(D)$ is uniformly bounded by $C \pi$ is quasi--normal of order…

Complex Variables · Mathematics 2020-06-11 Jürgen Grahl , Daniela Kraus , Oliver Roth

In this paper we prove some normality criteria for a family of meromorphic functions concerning shared analytic functions, which extend or generalized some result obtained by Y. F. Wang, M. L. Fang~\cite{WF} and J. Qui, T. Zhu ~\cite{QZ}.

Complex Variables · Mathematics 2019-06-10 Sanjay Kumar , Poonam Rani

A result is proved concerning meromorphic functions of finite order in the plane such that all but finitely many zeros of the second derivative are zeros of the first derivative.

Complex Variables · Mathematics 2013-06-20 J. K. Langley

In this paper, we continue to discuss normality based on a single\linebreak holomorphic function. We obtain the following result. Let $\CF$ be a family of functions holomorphic on a domain $D\subset\mathbb C$. Let $k\ge2$ be an integer and…

Complex Variables · Mathematics 2011-11-08 Xiaojun Liu , Shahar Nevo

We characterize normal families in the unit ball as those families of analytic functions whose restrictions to each complex line through the origin are normal. We then generalize this result to a characterization of normal functions…

Complex Variables · Mathematics 2026-01-29 Peter V Dovbush , Steven G Krantz

In this note, we consider meromorphic univalent functions $f(z)$ in the unit disc with a simple pole at $z=p\in(0,1)$ which have a $k$-quasiconformal extension to the extended complex plane $\hat{\mathbb C},$ where $0\leq k < 1$. We denote…

Complex Variables · Mathematics 2015-02-19 Bappaditya Bhowmik , Goutam Satpati , Toshiyuki Sugawa

In this article, we prove a normality criterion for a family of meromorphic functions having zeros with some multiplicity which involves sharing of a holomorphic function by the members of the family. Our result generalizes Montel's…

Complex Variables · Mathematics 2024-02-20 Gopal Datt , Sanjay Kumar

Let $f: B^n \rightarrow {\mathbb R}$ be a $d+1$ times continuously differentiable function on the unit ball $B^n$, with $\max_{z\in B^n} \| f(z) \|=1$. A well-known fact is that if $f$ vanishes on a set $Z\subset B^n$ with a non-empty…

Classical Analysis and ODEs · Mathematics 2023-09-11 Gil Goldman , Yosef Yomdin

Let ${\mathcal A}$ denote the family of all functions $f$ analytic in the unit disk $\ID$ and satisfying the normalization $f(0)=0= f'(0)-1$. Let $\mathcal{S}$ denote the subclass of ${\mathcal A}$ consisting of univalent functions in…

Complex Variables · Mathematics 2016-08-16 Milutin Obradović , Saminathan Ponnusamy , Karl-Joachim Wirths

Let $\mathcal{A}$ denote the class of analytic functions $f$ on the unit disc $\mathbb{D}=\{z\in\mathbb{C}:\;|z|<1\}$ normalized by $f(0)=0$ and $f^{\prime}(0)=1$. In the present article, we consider and $\mathcal{F}(c)$ the subclasses of…

Complex Variables · Mathematics 2025-06-26 Molla Basir Ahamed , Rajesh Hossain , Sabir Ahammed

This paper treats the class of normalized logharmonic mappings f(z) = zh(z)bar{g(z)} in the unit disk satisfying {\phi}(z) = zh(z)g(z) is analytically typically real. Every such mapping f is shown to be a product of two particular…

Complex Variables · Mathematics 2017-10-05 Najla M. Alarifi , Zayid Abdulhadi , Rosihan M. Ali

In this paper we generalize a result of Ye, Pang and Yang[12] on the normality of a family of holomorphic curves in $P^N(\mathbb{C})$. Further we obtain a normality criterion for family of meromorphic functions that partially share…

Complex Variables · Mathematics 2024-11-05 Sonam Mehta , Kuldeep Singh Charak