Abstract

Let S H role=presentation> S H S H S_{H} be the class of functions f = h + g ¯ role=presentation> f = h + g ¯ f = h + g ¯ f=h+\bar{g} that are harmonic univalent and sense-preserving in the open unit disk U = { z ∈ C : | z | 𝕌 = { z ∈ ℂ : | z | h , h , h, g role=presentation> g g g are analytic and f ( 0 ) = f z ′ ( 0 ) − 1 = 0 role=presentation> f ( 0 ) = f ′ z ( 0 ) − 1 = 0 f ( 0 ) = f z ′ ( 0 ) − 1 = 0 f(0)=f_{z}'(0)-1=0 in U . role=presentation> 𝕌 . U . \mathbb{U}. In this paper, we investigate the properties of some subclasses of S H role=presentation> S H S H S_{H} such that h ( z ) role=presentation> h ( z ) h ( z ) h(z) is a starlike (or convex) function defined by subordination. We provide coefficient estimates, extremal function, distortion and growth estimates of g role=presentation> g g g , growth, and Jacobian estimates of f role=presentation> f f f . We also obtain area estimates and covering theorems of the classes. The results presented here generalize some known results.

Highlights

  • Introduction and preliminariesFor two analytic functions f and g on U = {z ∈ C : |z| < 1} with f (0) = g(0), f is said to be subordinate to g if there exists an analytic function ω on U such that ω(0) = 0, |ω| < 1, and f (z) = g(ω(z)) (z ∈ U)

  • In 1994, Ma and Minda [20] obtained the Fekete–Szegö problem for the starlike function and convex function defined by subordination

  • We introduce some subclasses of SH, such that h(z) is a subclass of starlike functions defined by subordination

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Summary

Introduction

Let A be the class of functions h(z) that are analytic in U and let S denote the subclass of functions in A that are univalent in U. Denote by SH the class of univalent and harmonic functions f that are sense-preserving in U and has the form (see [3,5])

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