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This note examines sufficient conditions for the quasiconformal extendibility of harmonic mappings defined in the unit disk. It is demonstrated that a harmonic strongly starlike mapping admits a quasiconformal extension to the entire plane,…

Complex Variables · Mathematics 2025-09-03 Xiu-Shuang Ma

In the present paper, we obtain a more general conditions for univalence of analytic functions in the open unit disk U. Also, we obtain a refinement to a quasiconformal extension criterion of the main result.

Complex Variables · Mathematics 2013-02-19 Murat Çağlar , Halit Orhan

In this article, we obtain quasiconformal extensions of some classes of conformal maps defined either on the unit disc or on the exterior of it onto the extended complex plane. Some of these extensions have been obtained by constructing…

Complex Variables · Mathematics 2018-09-20 Bappaditya Bhowmik , Goutam Satpati

In this paper, we extend Ahlfors's univalent criteria and Ahlfors's quasiconformal extension for analytic functions to harmonic mappings defined in the unit disk. Moreover, we give a general quasiconformal extension of harmonic…

Complex Variables · Mathematics 2021-12-28 Xiao-Yuan Wang , Jin-Hua Fan , Zhen-Yong Hu , Zhi-Gang Wang

Given a quasiconformal mapping $f:\mathbb R^n\to\mathbb R^n$ with $n\ge2$, we show that (un-)boundedness of the composition operator ${\bf C}_f$ on the spaces $Q_{\alpha}(\mathbb R^n)$ depends on the index $\alpha$ and the degeneracy set of…

Functional Analysis · Mathematics 2016-08-09 Pekka Koskela , Jie Xiao , Yi Ru-Ya Zhang , Yuan Zhou

We prove that if the Schwarzian norm of a given complex-valued locally univalent harmonic mapping $f$ in the unit disk is small enough, then $f$ is, indeed, globally univalent and can be extended to a quasiconformal mapping in the extended…

Complex Variables · Mathematics 2014-10-21 Rodrigo Hernández , María J. Martín

The notion of $\Phi$-like functions is known to be a necessary and sufficient condition for univalence. By applying the idea, we derive several necessary conditions and sufficient conditions for that an analytic function defined on the unit…

Complex Variables · Mathematics 2011-11-29 Ikkei Hotta

We provide two new formulas for quasiconformal extension to $\overline{\mathbb{C}}$ for harmonic mappings defined in the unit disk and having sufficiently small Schwarzian derivative. Both are generalizations of the Ahlfors-Weill extension…

Complex Variables · Mathematics 2021-05-18 Iason Efraimidis , Rodrigo Hernández , María J. Martín

We derive a quasiconformal extension to 3-space of the Weierstrass-Enneper lifts of a class of harmonic mappings defined in the unit disk. The extension is based on fibrations of space by circles in domain and image that correspond to each…

Complex Variables · Mathematics 2014-04-17 Martin Chuaqui , Peter Duren , Brad Osgood

We investigate univalent functions $f(z)=z+a_2z^2+a_3z^3+\ldots$ in the unit disk $\mathbb D$ extendible to $k$-q.c.(=quasiconformal) automorphisms of $\mathbb C$. In particular, we answer a question on estimation of $|a_3|$ raised by…

Complex Variables · Mathematics 2019-05-22 Pavel Gumenyuk , Ikkei Hotta

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 1972, J. Becker [J. Reine Angew. Math. 255] discovered a sufficient condition for quasiconformal extendibility of Loewner chains. Many known conditions for quasiconformal extendibility of holomorphic functions in the unit disk can be…

Complex Variables · Mathematics 2020-06-09 Pavel Gumenyuk , István Prause

In this paper we introduce the notion of a quasi-modular and we prove that the respective Minkowski functional of the unit quasi-modular ball becomes a quasi-norm. In this way, we refer to and complete the well-known theory related to the…

Functional Analysis · Mathematics 2022-08-19 Paweł Foralewski , Henryk Hudzik , Paweł Kolwicz

We study conjugate-type phenomena for complex-valued harmonic quasiregular mappings in the unit disk across three function space families: $Q(n,p,\alpha)$, $F(p,q,s)$, and the non-derivative $M(p,q,s)$. For a harmonic $K$-quasiregular…

Complex Variables · Mathematics 2026-01-13 Jihua Sun , Junming Liu , Zhi-Gang Wang

This paper focuses on estimating the Taylor coefficients for Hilbert spaces of holomorphic functions on the disk using intrinsic features of univalent functions and of Teichmuller spaces. Estimating these coefficients has a long history but…

Complex Variables · Mathematics 2026-05-20 Samuel L Krushkal

We introduce a weaker variant of the concept of three point property, which is equivalent to a non-linear local connectivity condition introduced in [12], sufficient to guarantee the extendability of a conformal map f from the unit disk…

Complex Variables · Mathematics 2024-10-15 Changyu Guo

In this paper we give some sufficient conditions of analyticity and univalence for functions defined by an integral operator. Next, we refine the result to a quasiconformal extension criterion with the help of the Becker's method. Further,…

Complex Variables · Mathematics 2016-07-08 S. Kanas , E. Deniz , H. Orhan

This article contains several results for \lambda-Robertson functions, i.e., analytic functions $f$ defined on the unit disk $D$ satisfying $f(0) = f'(0)-1=0$ and $Re e^{-i\lambda} {1+zf"(z)/f'(z)} > 0$ in $D$, where $\lambda \epsilon…

Complex Variables · Mathematics 2010-06-29 Ikkei Hotta , Li-Mei Wang

By using the method of Loewner chains, we establish some sufficient conditions for the analyticity and univalency of functions defined by an integral operator. Also, we refine the result to a quasiconformal extension criterion with the help…

Complex Variables · Mathematics 2012-08-14 Murat Çağlar , Halit Orhan

The method of Grunsky inequalities has many applications and has been extended in many directions, even to bordered Riemann surfaces. However, unlike the case of functions univalent in the disk, a quasiconformal variant of this theory has…

Complex Variables · Mathematics 2013-07-31 Samuel L. Krushkal
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