Some properties of the class $\mathcal{U}$
Date Issued
2018-12-20
Author(s)
Milutin Obradovic
Nikola Tuneski
Abstract
In this paper we study the class $\mathcal{U}$ of functions that are analytic
in the open unit disk ${\mathbb D}=\{z:|z|<1\}$, normalized such that
$f(0)=f'(0)-1=0$ and satisfy \[\left|\left [\frac{z}{f(z)} \right]^{2}f'(z)-1
\right|<1\quad\quad (z\in {\mathbb D}).\] For functions in the class
$\mathcal{U}$ we give sharp estimate of the second ant the third Hankel
determinant, its relationship with the class of $\alpha$-convex functions, as
well as certain starlike properties.
in the open unit disk ${\mathbb D}=\{z:|z|<1\}$, normalized such that
$f(0)=f'(0)-1=0$ and satisfy \[\left|\left [\frac{z}{f(z)} \right]^{2}f'(z)-1
\right|<1\quad\quad (z\in {\mathbb D}).\] For functions in the class
$\mathcal{U}$ we give sharp estimate of the second ant the third Hankel
determinant, its relationship with the class of $\alpha$-convex functions, as
well as certain starlike properties.