Sufficient and necessary conditions for conformality. Part II. Analytic viewpoint

Autor: Melkana A. Brakalova
Rok vydání: 2010
Předmět:
Zdroj: Annales Academiae Scientiarum Fennicae Mathematica. 35:235-254
ISSN: 1798-2383
1239-629X
DOI: 10.5186/aasfm.2010.3514
Popis: This paper is dedicated in loving memory to V.V. Alexandrov and A.A. Gol'dberg. Abstract. This is the second of two papers devoted to the topic of conformality at a point and related notions in the plane. We derive representation formulas and estimates for the mod- ules of families of curves that are images of circles, radial segments and arcs of spirals under a "-homeomorphism. We use them to convert the extremal-length type sucient and necessary con- ditions for conformality at a point from Part I to analytic sucient conditions, that depend on directional dilatations and bypass the assumption of K-quaisconformality. Our results extend the Teichmuller-Wittich-Belinskii theorem, results of Reich and Walczak, the author and Jenkins, and Gutlyanskii and Martio. 1. Definitions and main results Conformality at a point (see (1.3)) and related notions in the plane are rich properties that have had applications in the theory of Riemann surfaces, Nevanlinna theory, in the study of regularity properties of the boundary correspondence, local modulus of continuity properties and others (e.g. (10, 15, 16, 17, 22, 26)). Our main results, Theorems 1.2-1.4, provide sucient
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