Acta mathematica scientia,Series B ›› 2022, Vol. 42 ›› Issue (2): 611-622.doi: 10.1007/s10473-022-0213-x

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THE SUBORDINATION PRINCIPLE AND ITS APPLICATION TO THE GENERALIZED ROPER-SUFFRIDGE EXTENSION OPERATOR

Jianfei WANG1, Xiaofei ZHANG2   

  1. 1. School of Mathematical Sciences, Huaqiao University, Quanzhou 362021, China;
    2. School of Mathematics and Statistics, Pingdingshan University, Pingdingshan 467000, China
  • Received:2020-07-16 Revised:2021-04-28 Online:2022-04-25 Published:2022-04-22
  • Supported by:
    The project was partially supported by the National Natural Science Foundation of China (12071161, 11971165, 11701307) and the Natural Science Foundation of Fujian Province (2020J01073).

Abstract: This note is devoted to applying the principle of subordination in order to explore the Roper-Suffridge extension operator and the Pfaltzgraff-Suffridge extension operator with special analytic properties. First, we prove that both the Roper-Suffridge extension operator and the Pfaltzgraff-Suffridge extension operator preserve subordination. As applications, we obtain that if β[0,1],γ[0,1r] and β+γ1, then the Roper-Suffridge extension operator

Φβ,γ(f)(z)=(f(z1),(f(z1)z1)β(f(z1))γw),zΩp,r
preserves an almost starlike mapping of complex order λ on Ωp,r={z=(z1,w)C×X:|z1|p+wXr<1}, where 1p2, r1 and X is a complex Banach space. Second, by applying the principle of subordination, we will prove that the Pfaltzgraff-Suffridge extension operator preserves an almost starlike mapping of complex order λ. Finally, we will obtain the lower bound of distortion theorems associated with the Roper-Suffridge extension operator. This subordination principle seems to be a new idea for dealing with the Loewner chain associated with the Roper-Suffridge extension operator, and enables us to generalize many known results from p=2 to 1p2.

Key words: Biholomorphic mappings, starlike mappings, subordination, Loewner chain

CLC Number: 

  • 32H02
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