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Proceedings of the American Mathematical Society
Article . 1975 . Peer-reviewed
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Subordination by convex functions

Authors: Stephan Ruscheweyh; D. J. Hallenbeck;

Subordination by convex functions

Abstract

The following theorem is proven: Let F ( z ) F(z) be convex and univalent in Δ = { z : | z | > 1 } , F ( 0 ) = 1 \Delta = \{ z:|z| > 1\} ,F(0) = 1 . Let f ( z ) f(z) be analytic in Δ , f ( 0 ) = 1 , f ′ ( 0 ) = … = f ( n − 1 ) ( 0 ) = 0 \Delta ,f(0) = 1,f’(0) = \ldots = {f^{(n - 1)}}(0) = 0 , and let f ( z ) ≺ F ( z ) f(z) \prec F(z) in Δ \Delta . Then for all γ ≠ 0 \gamma \ne 0 , Re γ ⩾ 0 \gamma \geqslant 0 , \[ γ z − γ ∫ 0 z τ γ − 1 f ( τ ) d τ ≺ γ z − γ / n ∫ 0 z 1 / n τ γ − 1 F ( τ n ) d τ . {\gamma _z}^{ - \gamma }\int _0^z {{\tau ^{\gamma - 1}}f(\tau )d\tau \prec \gamma {z^{ - \gamma /n}}\int _0^{{z^{1/n}}} {{\tau ^{\gamma - 1}}F({\tau ^n})d\tau .} } \] This theorem, in combination with a method of D. Styer and D. Wright, leads to the following Corollary. Let f ( z ) , g ( z ) f(z),g(z) be convex univalent in Δ , f ( 0 ) = f ( 0 ) = g ( 0 ) = g ( 0 ) = 0 \Delta ,f(0) = f(0) = g(0) = g(0) = 0 . Then f ( z ) + g ( z ) f(z) + g(z) is starlike univalent in Δ \Delta . Other applications of the theorem are concerned with the subordination of f ( z ) / z f(z)/z where f ( z ) f(z) belongs to certain classes of convex univalent functions.

Keywords

Special classes of univalent and multivalent functions of one complex variable (starlike, convex, bounded rotation, etc.), Extremal problems for conformal and quasiconformal mappings, other methods

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citations
This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Citations provided by BIP!
popularity
This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network.
BIP!Popularity provided by BIP!
influence
This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically).
BIP!Influence provided by BIP!
impulse
This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network.
BIP!Impulse provided by BIP!
168
Top 1%
Top 0.1%
Average
bronze
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