`Abstract and Applied AnalysisVolumeÂ 2012Â (2012), Article IDÂ 383592, 10 pageshttp://dx.doi.org/10.1155/2012/383592`
Research Article

## -Bazilevic Functions

Department of Mathematical Sciences, College of Science, Princess Nora bint Abdul Rahman University, P.O. Box 4384, Riyadh 11491, Saudi Arabia

Received 31 December 2011; Revised 2 March 2012; Accepted 3 March 2012

Copyright Â© 2012 F. M. Al-Oboudi. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

#### Abstract

The aim of this paper is to define and study a class of Bazilevic functions using the generalized Salagean operator. Some properties of this class are investigated: inclusion relation, some convolution properties, coefficient bounds, and other interesting results.

#### 1. Introduction

Let be the set of analytic functions in the open unit disc . Let be the set of functions , with , and let be the set of functions , with . Let be the class of functions , which are univalent in . Denote by , , the class of starlike (convex)(close-to-convex) functions of order . Note that when , then , let . A function , where belongs to the Kaplan class , , , [1] if for and .

The Dual of is defined as where denotes Hadamard product (convolution).

A set is called a test set for (denoted by ) if . Note that if , then .

Denote by the class of functions , such that , in , and let . Note that for , and that , , if, and only if, .

For and , define the class as Note that , , .

A function , is called prestarlike of order , , (denoted by ) if and only if , or if and only if

Let , , , denote the class of Bazilevic functions in , introduced by Bazilevic [2], , , , if and only if there exists a , such that for where at . We denote by . Bazilevic shows that , for , . Note that

For further information, see [3â€“7].

The generalized Salagean operator , , , is defined [8] as where

The Operator satisfies the following identity: Not that for , , Salagean differential operator [9].

Let we mean by , the solution of . Hence where . It is known [10] that , hence , and that

The class , is defined as if and only if . For , we get Salagean-type -starlike functions [9].

The operator is now called â€śAl-Oboudi Operatorâ€ť and has been extensively studied latly, [5, 11, 12].

In this paper we define and study a class of Bazilevic functions using the operator and study some of its basic properties, inclusion relation, convolution properties coefficient bounds, and other interesting results.

#### 2. Definition and Preliminaries

In this section, the class of -Bazilevic functions , , where , is defined and some preliminary lemmas are given.

##### 2.1. Definition

Let . Then , , , if and only if there exists a , such that where the power is chosen as a principal one.

Denote by the class of functions , where .

Using (1.10), we see that , from which the following special cases are clear.

###### 2.1.1. Special Cases
(1)For , , , Bazilevic [2].(2)For , , Salagean type close to convex functions, Blezu [13].(3)For , , , Kaplan [14].(4)For , , Abdul Halim [15] and , Opoola [16].
##### 2.2. Lemmas

The following lemmas are needed to prove our results.

Lemma 2.1 (see [10]). Let and , . Then for

Lemma 2.2. If , , then .

Proof. Since , we will show that . Now , implies Hence From (1.13), we get the required result.

Lemma 2.3 (see [1]). Let and , . Then .

For , let denote the largest positive number so that every is convex in . The following result is due to Al-Amiri [17].

Lemma 2.4. One has

Lemma 2.5 (see [18]). Let , with and . Let in , where Then for each , where stands for closed convex hull.

Remark 2.6. In [1], it was shown that condition (2.6) is satisfied for all in whenever is in and is in .

Lemma 2.7 (see [10]). Let be such that and let , , . Then

From (1.12) and (1.13), we immediately have;

Lemma 2.8. One has

Lemma 2.9 (see [10]). Let , . Then where stands for coefficient majorization.

#### 3. Main Results

Theorem 3.1. One has

Proof. Let . Then there exists , such that Hence Since , and , application of Lemma 2.3 gives hence Using Lemma 2.2 we deduce that .
As a consequence of (3.1) we immediately have the following.Corollary 3.2. One has

Corollary 3.3. If , , , then, for

Proof. Since , there exists a or such that using (1.3). From (3.6), we conclude that which implies that Applying Lemma 2.3 to (3.9), we get the result.

Theorem 3.4. Let . Then

Proof. From (2.1), we see that Since , and , then which is the required result.

In the following we prove the converse of Theorem 3.1, for .

Theorem 3.5. Let , . Then in , where is given by (2.5)

Proof. implies (2.1), where .
Now Using Lemma 2.4, we see that in , for , where is given by (2.5).
From Remark 2.6, we conclude
Applying Lemma 2.5, we deduce hence in , as required.

Corollary 3.3 can be improved for , as follows.

Theorem 3.6. Let , . Then

Proof. We will use Ruscheweyhâ€™s.method of proof [10]. implies (3.8), where , .
Let , where and .
Then and . This implies
Using Lemma 2.7, we get
Hence To prove that , we have to show that , or equivalently .
Since , then from (1.5) From Lemma 2.8, (1.13), and (3.22), we see that . Using (3.21), we obtain . From (1.1) we get the required result.

Remark 3.7. For , Theorem 3.6 and other stronger results depending on , are proved by Sheil-Small [7].

For the coefficient bounds of , Theorem 3.6 is not strong enough to settle this problem for , In 1962, Zamorski [19] proved the Bieberbach conjecture for , when , in the following we prove this result for , using the extreme points of Kaplan class .

Theorem 3.8. For , ,

Proof. From (3.9) and Lemma 2.9, we get using (2.10). Raising both sides of (3.24) to the th power, where , we get the required result.

Remark 3.9. For , we get the result of Zamorski [19], and the result of Sheil-Small [7], from which we get the idea of proof.

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