Logarithmic coefficients for certain subclasses of close-to-convex functions

被引:40
作者
Kumar, U. Pranav [1 ]
Vasudevarao, A. [2 ]
机构
[1] Indian Inst Technol Kharagpur, Dept Mech Engn, Kharagpur 721302, W Bengal, India
[2] Indian Inst Technol Kharagpur, Dept Math, Kharagpur 721302, W Bengal, India
来源
MONATSHEFTE FUR MATHEMATIK | 2018年 / 187卷 / 03期
关键词
Analytic; Univalent; Starlike; Convex and close-to-convex functions; Coefficient estimates; Logarithmic coefficients; Primary; 30C45; 30C50; UNIVALENT-FUNCTIONS;
D O I
10.1007/s00605-017-1092-4
中图分类号
O1 [数学];
学科分类号
0701 ; 070101 ;
摘要
Let S denote the class of functions analytic and univalent (i.e. one-to-one) in the unit disk D = {z is an element of C : vertical bar z vertical bar < 1} normalized by f (0) = 0 = f'(0) - 1. The logarithmic coefficients gamma(n) of f is an element of S are defined by log f (z)/z = 2 Sigma(infinity)(n=1) gamma(n)z(n). Let F-1(F-2 and F-3 resp.) denote the class of functions f is an element of A such that Re (1-z) f'(z) > 0 (Re (1 - z(2)) f' (z) > 0 and Re (1 - z + z(2)) f' (z) > 0 resp.) in D. The classes F-1, F-2 and F-3 are subclasses of the class of close-to-convex functions. In the present paper, we determine the sharp upper bound for vertical bar gamma(1)vertical bar, vertical bar gamma(2)vertical bar and vertical bar gamma(3)vertical bar for functions f in the classes F-1, F-2 and F-3.
引用
收藏
页码:543 / 563
页数:21
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