Geometric properties of a class of support points of univalent functions

Author:

Brown Johnny E.

Abstract

Let S denote the set of functions f ( z ) f(z) analytic and univalent in | z | > 1 |z|\, > \,1 , normalized by f ( 0 ) = 0 f(0)\, = \,0 and f ( 0 ) = 1 f’(0)\, = \,1 . A function f is a support point of S if there exists a continuous linear functional L, nonconstant on S, for which f maximizes Re Re L ( g ) \operatorname {Re} \,L(g) , g S g \in S . The support points corresponding to the point-evaluation functionals are determined explicitly and are shown to also be extreme points of S. New geometric properties of their omitte arcs Γ \operatorname {arcs}\,\Gamma are found. In particular, it is shown that for each such support point Γ \Gamma lies entirely in a certain half-strip, Γ \Gamma has monotonic argument, and the angle between radius and tangent vectors increases from zero at infinity to a finite maximum value at the tip of the arc Γ \operatorname {arc}\,\Gamma . Numerical calculations appear to indicate that the known bound π / 4 \pi /4 for the angle between radius and tangent vectors is actually best possible.

Publisher

American Mathematical Society (AMS)

Subject

Applied Mathematics,General Mathematics

Reference10 articles.

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1. [127] (with P. L. Duren and Y. J. Leung) Support points with maximum radial angle;Menahem Max Schiffer: Selected Papers Volume 2;2013-08-28

2. A New Approach to Support Point Theory for the Class $$\mathcal{S}$$;Computational Methods and Function Theory;2005-08

3. The Existence of a Waver Point on the Omitted Arc of a Support Point of the Class S;Complex Variables, Theory and Application: An International Journal;2003-01

4. Truncation of support points for univalent functions;Complex Variables, Theory and Application: An International Journal;1984-03

5. Support Points with Maximum Radial Angle;Complex Variables, Theory and Application: An International Journal;1983-02

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