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THE MODULUS OF THE IMAGE ANNULI UNDER UNIVALENT HARMONIC MAPPINGS AND A CONJECTURE OF NITSCHE

Published online by Cambridge University Press:  30 October 2001

ABDALLAH LYZZAIK
Affiliation:
Department of Mathematics, American University of Beirut, Beirut, Lebanon; [email protected]
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Abstract

The object of the paper is to show that if f is a univalent, harmonic mapping of the annulus A(r, 1) = {z : r < [mid ]z[mid ] < 1} onto the annulus A(R, 1), and if s is the length of the segment of the Grötzsch ring domain associated with A(r, 1), then R < s. This gives the first, quantitative upper bound of R, which relates to a question of J. C. C. Nitsche that he raised in 1962. The question of whether this bound is sharp remains open.

Type
Research Article
Copyright
The London Mathematical Society 2001

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