Abstract
The prime purpose of this article is to derive a necessary and sufficient condition for a linear operator associated with the Pascal distribution series to be in the class of analytic functions. Moreover, inclusion relation and an integral operator linked to the Pascal distribution series is considered. We have also provided some results as corollaries of our theorems.
1. Introduction and Class Definition
Let be the set of all complex numbers. We denote by , the set of all analytic functions in the unit disk that have the series of the form.
For functions given by (1) and given by , we recall that the well-known Hadamard product of and is given by.
For and , we say that a function lies in the class if
The function class was introduced in [1].
In [2], Magesh and Prameela defined the following class:
Definition 1. A function lies in the class if the following inequality is satisfied.where , , and .
We also letwhere is be a subclass of consisting of functions of the formWe note that, by specializing the parameters and , we obtain the following subclasses studied by various authors.(1) and (Silverman [3])(2) (Al-Amiri [4], Gupta and Jain [5] and Sarangi and Uralegaddi [6])(3) (Rosy [7] and Stephen and Subramanian [8])(4) and (Bharati et al. [9])(5) (Subramanian et al. [10])(6) (Subramanian et al. [11])In [12], El-Deeb et al. provided a power series expansion whose coefficients are related to the probabilities of the Pascal distribution.where . We also define the seriesNext, let us consider the linear operatordefined by means of the convolution or Hadamard product.Several results on the engagements between different subclasses of analytic univalent functions and special functions or distribution series have been studied in the literature (see for example, [13–27]). Herein, we provide a necessary and sufficient condition for to be in the aforementioned class and investigate an inclusion property of the class associated with the operator . Ultimately, we provide conditions for the integral operator to be in the investigated class .
We shall need the following lemmas to state and prove our results.
Lemma 1. (see [2]). Given that and . A function belongs to the class if and only if the following inequality is satisfied.where
The result is sharp for the function.
Lemma 2. (see [1]). If lies in the class , then
The result is sharp.
2. The Necessary and Sufficient Condition
Throughout this paper, we use significantly the following identities for and .
Using Lemma 1, we get the following necessary and sufficient condition for to be in the investigated class .
Theorem 1. For , if and only if
Proof. From Lemma 1, we only need to show thatPutting and , in (17), we haveBut this last expression is bounded previously by if and only if (16) is satisfied.
3. Inclusion Properties
Next, we show that .
Theorem 2. For and if
Proof. According to Lemma 1, it suffices to prove thatApplying Lemma 2, we find from (14) and (20) thatThus, the proof is completed since the RHS of the above inequality is bounded by .
4. An Integral Operator
In this section, we will consider the following integral operator.
Theorem 3. For , if and only if
Proof. From (8) and (22), we easily getThen using Lemma 1, we only need to prove that.Clearly, we haveThe rest of the proof can be made similar to that of Theorem 2.
5. Corollaries and Consequences
Letting in Theorems 1–3, one can get the following corollaries.
Corollary 1. For , if and only if
Corollary 2. for and if
Corollary 3. For , the integral operator given by (22) is in the class if and only if
6. Conclusions
In the present paper and due the earlier works (see, for example, [12, 15, 21]), we find a necessary and sufficient condition and inclusion relation for Pascal distribution series to be in a class of analytic functions with negative coefficients. Furthermore, we consider an integral operator related to Pascal distribution series. Some interesting corollaries and applications of the results are also discussed.
Data Availability
No data were used to support this study.
Conflicts of Interest
The authors declare that they have no conflicts of interest.