• Title/Summary/Keyword: Zalcman functional

Search Result 2, Processing Time 0.014 seconds

Some Coefficient Inequalities Related to the Hankel Determinant for a Certain Class of Close-to-convex Functions

  • Sun, Yong;Wang, Zhi-Gang
    • Kyungpook Mathematical Journal
    • /
    • v.59 no.3
    • /
    • pp.481-491
    • /
    • 2019
  • In the present paper, we investigate the upper bounds on third order Hankel determinants for certain class of close-to-convex functions in the unit disk. Furthermore, we obtain estimates of the Zalcman coefficient functional for this class.

GEOMETRIC PROPERTIES ON (j, k)-SYMMETRIC FUNCTIONS RELATED TO STARLIKE AND CONVEX FUNCTION

  • Gochhayat, Priyabrat;Prajapati, Anuja
    • Communications of the Korean Mathematical Society
    • /
    • v.37 no.2
    • /
    • pp.455-472
    • /
    • 2022
  • For j = 0, 1, 2,…, k - 1; k ≥ 2; and - 1 ≤ B < A ≤ 1, we have introduced the functions classes denoted by ST[j,k](A, B) and K[j,k](A, B), respectively, called the generalized (j, k)-symmetric starlike and convex functions. We first proved the sharp bounds on |f(z)| and |f'(z)|. Various radii related problems, such as radius of (j, k)-symmetric starlikeness, convexity, strongly starlikeness and parabolic starlikeness are determined. The quantity |a23 - a5|, which provide the initial bound on Zalcman functional is obtained for the functions in the family ST[j,k]. Furthermore, the sharp pre-Schwarzian norm is also established for the case when f is a member of K[j,k](α) for all 0 ≤ α < 1.