Abstract

The main objective of the present paper is to study the mapping properties of functions belonging to certain classes under a family of univalent and starlike integral operator. Relationships of these classes are also pointed out.

1. Introduction and Definitions

Let denotes the class of functions normalized by which are analytic in the open unit disk Also let denotes the class of all functions in which are univalent in . Then a function is said to be starlike in if and only if We denote by the class of all functions in which are starlike in . A function is said to be starlike of order in if and only if for some . We denote by the class of all functions in which are starlike of order in . Clearly, we have .

With a view to introducing an interesting family of analytic functions, we should recall the concept of subordination between analytic functions. Given two functions and , which are analytic in , the function is said to be subordinate to if there exists a function , analytic in with and    such that , , and symbolically written as the following:

It is known that    and .

Definition 1 (see [1]). For , a function , analytic in with , is said to belong to the class if

To prove our main result, we need the following.

Lemma 2 (see [2]). Let the functions and be analytic in , and let map onto a starlike region. Suppose also that Then, for all .

Lemma 3 (see [3]). Let Then, for and , for all .

Lemma 4 (see [4]). Let the functions and be analytic in with and let be a real number. Suppose also that maps onto a region which is starlike with respect to the origin. Then,

2. Main Result

We begin by introducing a new integral operator where and .

Bear in mind, there are various types of integral operators studied by many different authors such as [5–9], few to mention, that motivate us to come out with the abovementioned integral operators.

Now let us begin with our first result relating to the integral operator of (13).

Theorem 5. Let the functions and be in the class . Then, the function defined by (13) is also in the class .

Proof. By logarithmic differentiation, we find from (13) that where Clearly, we have , and satisfies the starlikeness condition of Lemma 4.
Next, let , where is analytic function in , and . From (15), it is easily seen that hence by Lemma 4, we obtain that is which evidently proves Theorem 5.

Theorem 6. Let the functions and be in the class . Then, is in the class .

Proof. Since we find from Definition 1 that By logarithmic differentiation, we find from (13) that where Next, let , and from (15), it is easily seen that Now rewrite the equality in (23) in the form so that by (20) and Lemma 3, we have It is easily seen that and satisfy conditions of Lemma 2. It follows from (21), (25), and Lemma 2 that which evidently proves Theorem 6.

Acknowledgment

The work presented here was supported by LRGS/TD/2011/UKM/ICT/03/02.