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On bounded univalent functions that omit two given values

Dimitrios Betsakos (1999)

Colloquium Mathematicae

Let a,b ∈ z: 0<|z|<1 and let S(a,b) be the class of all univalent functions f that map the unit disk into {a,bwith f(0)=0. We study the problem of maximizing |f’(0)| among all f ∈ S(a,b). Using the method of extremal metric we show that there exists a unique extremal function which maps onto a simply connnected domain D 0 bounded by the union of the closures of the critical trajectories of a certain quadratic differential. If a<0

On certain coefficient bounds for multivalent functions

Fatma Altuntaş, Muhammet Kamali (2009)

Annales UMCS, Mathematica

In the present paper, the authors obtain sharp upper bounds for certain coefficient inequalities for linear combination of Mocanu α-convex p-valent functions. Sharp bounds for [...] and [...] are derived for multivalent functions.

On certain general integral operators of analytic functions

B. Frasin (2012)

Annales UMCS, Mathematica

In this paper, we obtain new sufficient conditions for the operators Fα1,α2,…,αn,β(z) and Gα1,α2,…,αn,β(z) to be univalent in the open unit disc U, where the functions f1, f2, …, fn belong to the classes S*(a, b) and K(a, b). The order of convexity for the operators Fα1,α2,…,αn,β(z) and Gα1,α2,…,αn,β(z) is also determined. Furthermore, and for β = 1, we obtain sufficient conditions for the operators Fn(z) and Gn(z) to be in the class K(a, b). Several corollaries and consequences of the main results...

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