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The Grunsky operator arises from univalence and plays a crucial role in geometric function theory. This operator also implies quasiconformal extendibility and has an intrinsic connection with Teichmuller space theory and its interactions…

Complex Variables · Mathematics 2024-12-12 Samuel L. Krushkal

We establish that the Grunsky norm of any normalized univalent function on the disk is completely determined by the squares of holomorphic abelian differentials (in contrast to the Teichmuller norm, which relates to all integrable…

Complex Variables · Mathematics 2023-05-05 Samuel L. Krushkal

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

Let function $f$ be normalized, analytic and univalent in the unit disk ${\mathbb D}=\{z:|z|<1\}$ and $f(z)=z+\sum_{n=2}^{\infty} a_n z^n$. Using a method based on Grusky coefficients we study several problems over that class of univalent…

Complex Variables · Mathematics 2025-05-29 Milutin Obradović , Nikola Tuneski

Ruscheweyh extended the work of Becker and Ahlfors on sufficient conditions for a normalized analytic function on the unit disk to be univalent there. In this paper we refine the result to a quasiconformal extension criterion with the help…

Complex Variables · Mathematics 2009-11-19 Ikkei Hotta

Recently the author has presented a new approach to solving extremal problems of geometric function theory. It involves the Bers isomorphism theorem for Teichmuller spaces of punctured Riemann surfaces. We show here that this approach,…

Complex Variables · Mathematics 2020-04-01 Samuel L. Krushkal

In this paper we study a multiplier operator which is induced by the Schwarzian derivative of univalent functions with a quasiconformal extension to the extended complex plane. As applications, we show that the Brennan conjecture is…

Complex Variables · Mathematics 2024-07-09 Jianjun Jin

We consider certain subfamilies, of the family of univalent functions in the open unit disk, defined by means of sufficient coefficient conditions for univalency. This article is devoted to studying the problem of the well-known conjecture…

Complex Variables · Mathematics 2016-04-20 Sarita Agrawal , Swadesh Kumar Sahoo

Let $\mathcal{S}$ denote the class of functions $f$ which are analytic and univalent in the unit disk ${\mathbb D}=\{z:|z|<1\}$ and normalized with $f(z)=z+\sum_{n=2}^{\infty} a_n z^n$. Using a method based on Grusky coefficients we study…

Complex Variables · Mathematics 2022-01-20 Milutin Obradović , Nikola Tuneski

A collection of infinite dimensional complete vector fields $\left\{V_i\right\}_{i=1}^{\infty}$ acting on a locally convex manifolds $M$ on which a smooth positive measure $\mu$ is defined was considered. It was assumed that the vector…

Functional Analysis · Mathematics 2025-10-23 M. E. Egwe , J. I. Opadara

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

We investigate the invariant metrics and complex geodesics in the universal Teichm\"{u}ller space and Teichm\"{u}ller space of the punctured disk using Milin's coefficient inequalities. This technique allows us to establish that all…

Complex Variables · Mathematics 2014-05-20 Samuel L. Krushkal

Consider a multiply-connected domain $\Sigma$ in the sphere bounded by $n$ non-intersecting quasicircles. We characterize the Dirichlet space of $\Sigma$ as an isomorphic image of a direct sum of Dirichlet spaces of the disk under a…

Complex Variables · Mathematics 2019-03-27 David Radnell , Eric Schippers , Wolfgang Staubach

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

We obtain explicit expressions for differential operators defining the action of the Virasoro algebra on the space of univalent functions. We also obtain an explicit Taylor decomposition for Schwarzian derivative and a formula for the…

Representation Theory · Mathematics 2012-11-27 Helene Airault , Yuri A. Neretin

The well-known Zalcman conjecture, which implies the Bieberbach conjecture, states that the coefficients of univalent functions $f(z) = z + \sum\limits_2^{\infty} a_n z^n$ on the unit disk satisfy $|a_n^2 - a_{2n-1}| \le (n-1)^2$ for all $n…

Complex Variables · Mathematics 2026-01-16 Samuel L. Krushkal

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

An important open problem in geometric complex analysis is to find algorithms for explicit determination of basic functionals intrinsically connected with conformal and quasiconformal maps, such as their Teichmuller and Grunsky norms,…

Complex Variables · Mathematics 2018-06-08 Samuel L. Krushkal

Estimating the coefficient functionals on various classes of holomorphic functions traditionally forms an important field of geometric complex analysis and its mathematical and physical applications. These coefficients reflect fundamental…

Complex Variables · Mathematics 2025-07-29 Samuel L. Krushkal

To a conformal map $f$ from the disk $\mathbb{D}$ into the complex plane onto a domain with rectifiable Ahlfors-regular boundary, we associate a new kind of Grunsky operator on the Hardy space of the unit disk. This is analogous to the…

Complex Variables · Mathematics 2023-11-23 Peter Kristel , Eric Schippers , Wolfgang Staubach
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