Extremal Problems in the Class of Starlike Functions1
نویسنده
چکیده
In an earlier paper [l] the writer showed the development of a variational method for starlike functions and applied this method to a general class of extremal problems connected with the coefficients of the function. It is the purpose of this paper to study the classes of extremal problems to which this variational method can be applied and to make some remarks as to its utility. The class S* of starlike functions is the class of all functions analytic and schlicht in the unit circle, normalized by /(0)=0 and /'(0) = 1, and mapping the unit circle onto a domain which is starshaped with respect to the origin. In [l] it was shown that given any function f(z) E S* a variation can be made within the class S* giving a change in the function
منابع مشابه
Starlikeness associated with parabolic regions
A parabolic starlike function f of order ρ in the unit disk is characterized by the fact that the quantity z f ′(z)/ f (z) lies in a given parabolic region in the right half-plane. Denote the class of such functions by PS∗(ρ). This class is contained in the larger class of starlike functions of order ρ. Subordination results for PS∗(ρ) are established, which yield sharp growth, covering, and di...
متن کاملAn upper bound to the second Hankel functional for the class of gamma-starlike functions
The objective of this paper is to obtain an upper bound to the second Hankel determinant $|a_{2}a_{4}-a_{3}^{2}|$ for the function $f$, belonging to the class of Gamma-starlike functions, using Toeplitz determinants. The result presented here include two known results as their special cases.
متن کاملUniformly Starlike and Convex Functions with Negative Coefficients
Let A(ω) be the class of analytic functions of the form: f(z) = (z − ω) + ∞ ∑ k=2 ak(z − ω) defined on the open unit disk U = {z : |z| < 1} normalized with f(ω) = 0, f ′(ω)−1 = 0 and ω is an arbitrary fixed point in U. In this paper, we define a subclass of ω − α − uniform starlike and convex functions by using a more generalized form of Ruschewey derivative operator. Several properties such as...
متن کاملChain hexagonal cacti: extremal with respect to the eccentric connectivity index
In this paper we present explicit formulas for the eccentric connectivity index of three classes of chain hexagonal cacti. Further, it is shown that the extremal chain hexagonal cacti with respect to the eccentric connectivity index belong to one of the considered types. Some open problems and possible directions of further research are mentioned in the concluding section.
متن کاملStarlike Functions of order α With Respect To 2(j,k)-Symmetric Conjugate Points
In this paper, we introduced and investigated starlike and convex functions of order α with respect to 2(j,k)-symmetric conjugate points and coefficient inequality for function belonging to these classes are provided . Also we obtain some convolution condition for functions belonging to this class.
متن کامل