English

On certain subclasses of close-to-convex functions related with the second-order differential subordination

Complex Variables 2019-07-19 v2

Abstract

Let A\mathcal{A} be the family of analytic and normalized functions in the open unit disc z<1|z|<1. In this article we consider the following classes \begin{equation*} \mathcal{R}(\alpha,\beta):=\left\{ f\in \mathcal{A}: {\rm Re}\left\{f'(z)+\frac{1+e^{i\alpha}}{2}zf''(z)\right\}>\beta,\, |z|<1\right\} \end{equation*} and \begin{equation*} \mathcal{L}_\alpha(b):=\left\{f\in\mathcal{A}:\left|f'(z) +\frac{1+e^{i\alpha}}{2}zf''(z)-b\right|< b,\, |z|<1 \right\}, \end{equation*} where π<απ-\pi<\alpha\leq \pi, 0β<10\leq \beta<1 and b>1/2b>1/2. We show that if fR(α,β)f\in \mathcal{R}(\alpha,\beta), then Re{f(z)}{\rm Re}\{f'(z)\} and Re{f(z)/z}{\rm Re}\{f(z)/z\} are greater than β\beta, and if fLα(b)f\in\mathcal{L}_\alpha(b), then 0<Re{f(z)}<2b0<{\rm Re}\{f'(z)\}<2b. Also, some another interesting properties of the class Lα(b)\mathcal{L}_\alpha(b) are investigated. Finally, the radius of univalence of 2-th section sum of fR(α,β)f\in \mathcal{R}(\alpha,\beta) is obtained.

Keywords

Cite

@article{arxiv.1901.02670,
  title  = {On certain subclasses of close-to-convex functions related with the second-order differential subordination},
  author = {Hesam Mahzoon and Rahim Kargar},
  journal= {arXiv preprint arXiv:1901.02670},
  year   = {2019}
}

Comments

9 pages, 1 figure. arXiv admin note: substantial text overlap with arXiv:1809.03022