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Subordination-implication problems concerning the nephroid starlikeness of analytic functions

  • Anbhu Swaminathan EMAIL logo and Lateef Ahmad Wani
From the journal Mathematica Slovaca

Abstract

Let A be the set of all analytic functions f defined on the open unit disk D satisfying f(0) = f'(0) 1 = 0. Let φNe(z) := 1 + z − z3=3 be the recently introduced Carathéodory function which maps the unit circle D D onto a 2-cusped kidney-shaped curve called nephroid given by ((u1)2+v24a)34v22=0. In this paper, we determine the best possible estimate on the real β so that for some analytic p satisfying p(0) = 1 the following subordination-implication holds:

1+βzp(z)pj(z)F(z)p(z)φNe(z),j=0,1,2,

where F(z) is some Carathéodory function with special geometries like right/left-half of Bernoulliφs lemniscate, cardioid, lune, eight-shaped, etc. As applications, we establish sufficient conditions for the Ma-Minda family of nephroid starlike functions given by

SNe*:={ fA:zf(z)f(z)φNe(z) }.
MSC 2010: Primary 30C45; 30C80

This work was supported by the Project No. CRG/2019/000200/MS of Science and Engineering Research Board (SERB), Department of Science and Technology (DST), New Delhi, India.


Acknowledgement

The authors would like to express their gratitude to the anonymous referees for their thoughtful comments and efforts towards improving the paper.

  1. (Communicated by Stanisława Kanas)

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Received: 2021-04-13
Accepted: 2021-09-11
Published Online: 2022-10-16
Published in Print: 2022-10-26

© 2022 Mathematical Institute Slovak Academy of Sciences

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