On a certain subclass of strongly starlike functions (1811.01271v2)

Abstract: Let $\mathcal{S}^*_t(\alpha_1,\alpha_2)$ denote the class of functions $f$ analytic in the open unit disc $\Delta$, normalized by the condition $f(0)=0=f'(0)-1$ and satisfying the following two--sided inequality: \begin{equation*} -\frac{\pi\alpha_1}{2}< \arg\left{\frac{zf'(z)}{f(z)}\right} <\frac{\pi\alpha_2}{2} \quad (z\in\Delta), \end{equation*} where $0<\alpha_1,\alpha_2\leq1$. The class $\mathcal{S}^*_t(\alpha_1,\alpha_2)$ is a subclass of strongly starlike functions of order $\beta$ where $\beta=\max{\alpha_1,\alpha_2}$. The object of the present paper is to derive some certain inequalities including (for example), upper and lower bounds for ${\rm Re}{zf'(z)/f(z)}$, growth theorem, logarithmic coefficient estimates and coefficient estimates for functions $f$ belonging to the class $\mathcal{S}^*_t(\alpha_1,\alpha_2)$.