Problems Concerning Coefficients of Symmetric Starlike Functions Connected with the Sigmoid Function

Abstract

In numerous geometric and physical applications of complex analysis, estimating the sharp bounds of coefficient-related problems of univalent functions is very important due to the fact that these coefficients describe the core inherent properties of conformal maps. The primary goal of this paper was to calculate the sharp estimates of the initial coefficients and some of their combinations (the Hankel determinants, Zalcman’s functional, etc.) for the class of symmetric starlike functions linked with the sigmoid function. Moreover, we also determined the bounds of second-order Hankel determinants containing coefficients of logarithmic and inverse functions of the same class.

Keywords

• starlike functions
• sigmoid function
• logarithmic and inverse functions
• Krushkal and Zalcman functionals
• Hankel determinant problems