Radii of starlikeness and convexity of generalized $k-$Bessel functions (1902.09979v2)

Abstract: The main purpose of this paper is to determine the radii of starlikeness and convexity of the generalized $\emph{k}-$Bessel functions for three different kinds of normalization by using their Hadamard factorization in such a way that the resulting functions are analytic in the unit disk of the complex plane. The characterization of entire functions from Laguerre-P\'olya class plays an crucial role in this paper. Moreover, the interlacing properties of the zeros of $\emph{k}-$Bessel function and its derivative is also useful in the proof of the main results. By making use of the Euler-Rayleigh inequalities for the real zeros of the generalized $\emph{k}-$Bessel function, we obtain some tight lower and upper bounds for the radii of starlikeness and convexity of order zero.