Abstract
In this study, we establish sufficient conditions for determining when linear operators related to the Pascal distribution series belong to various subclasses of univalent functions. Our findings are based on applying a coefficient bound from a specific class of analytic functions, providing valuable insights into the behavior of these functions under transformation.
Keywords:
univalent functions; starlike functions; convex functions; spirallike functions; pascal distribution series MSC:
30C45; 30C50; 33C90
1. Introduction
The Pascal distribution series [1], a fundamental component of probability theory, is extensively employed in statistics to construct generating functions that effectively model various probability and counting processes. This series is not only pivotal in these areas but also significantly contributes to the study of analytic functions, particularly in exploring essential properties such as univalence, starlikeness, and convexity.
Moreover, the Pascal distribution series serves as a foundation for deriving linear operators within geometric function theory, which enhances our understanding of the geometric behavior of functions. For instance, El-Deeb et al. [1] formulated a power series that links its coefficients to the Pascal distribution, allowing researchers to investigate the influence of these coefficients on the geometrical properties of univalent functions. This connection not only deepens our insight into the characteristics of such functions but also fosters further exploration in the field of geometric function theory. The Pascal distribution is described as follows to give additional context:
A variable y is said to follow a Pascal distribution [1] if it assumes values with specific associated probabilities,
respectively, here s and d are termed as the parameters. So, then
In [1], the Pascal distribution series derived as
where and .
In complex analysis, researchers have applied the Pascal distribution (refer to [1,2,3,4] and reference therein) series to define subclasses of univalent functions, establishing sufficient conditions for these functions to be starlike or convex. This field is still evolving, with ongoing research focused on deriving new bounds. Its use deepens insights into transformation properties, conformal mappings, and harmonic structures, making it an essential tool for exploring complex structures in geometric contexts. Starlike and convex functions, which have applications in conformal mappings and geometric function theory, often have constraints on their series coefficients. By using the Pascal distribution series in generating the linear operators, researchers can derive necessary and sufficient conditions for different subclasses of univalent functions.
Let consider a function defined as
and represent the class of all functions given in (1), that are analytic in the open unit disk , where . Moreover, the classes , , and (as described in [5]) represent the classes of univalent, starlike, and convex functions, respectively, and the analytic characterizations for these classes are given as follows:
Let is said to be starlike of order () if it satisfies the following condition:
and convex of order if it satisfies the following condition:
For the classes and .
A function is said to be uniformly starlike in the unit disk if for every circular arc , with center contained in then is also starlike with respect to in . We denote the class of uniformly starlike functions with .
A function is said to be uniformly convex in if for every circular arc with center in then is also convex in . We use to denote the class of uniformly convex functions.
Additionally, consider a class of uniformly convex of order , denoted as , which is defined in [6] as follows.
Definition 1
([6]). Let , with and , then
Note that, if then , and if then , known as classes of uniformly convex functions (see [7,8,9]).
A related class, denoted by , is defined using the Alexander transform. Specifically, belongs to . If , then (see [10]).
Definition 2
([11]). Let and , then
Definition 3
([12]). When , the classes and are defined in the following manner
and
Definition 4
([13]). A function is in
further, is in ⇔
where , .
The subclasses and extend various other subclasses of univalent functions by appropriately modifying the parameters. This leads us to observe that
- i.
- and , () (see [6]).
- ii.
- and . (see [10,14]).
- iii.
- and . (see [15]).
- iv.
- and . (see [16]).
Definition 5
([17]). A function is considered spirallike if there exists an angle ϑ such that and the following condition holds for all
Definition 6
([18,19]). For , and , the classes and are defined accordingly:
If , then (see [20])
Definition 7
([21]). For and , and are defined as follows:
and
If then and (see [22]).
Definition 8
([23,24]). Let , if and then
- .
Next, we are considering a subclass of , denoted by which was introduced and studied in [25].
Definition 9
([25]). Let , with and , if and then
The coefficient bound for the function is:
Similarly, if
then
If , then the Hadamard product [5] of and be defined as
where and .
Now, let us define the convolution operator using Hadamard product as
Recall the notion of the Pochhammer symbol, which is defined as
The study of special functions like hypergeometric functions (refer to [25,26,27,28,29]), confluent hypergeometric functions (refer to [30,31]), Wright’s function (refer to [32]), and generalized Bessel functions (refer to [33,34]), has garnered significant interest in Geometric Function Theory. Porwal ([3]) introduced the Poisson distribution series and demonstrated its intriguing applications within univalent functions. Following this, researchers expanded on this work by introducing series based on other distributions, such as the hypergeometric distribution (refer to [35]), confluent hypergeometric distribution (refer to [36]), Binomial distribution (refer to [37]), generalized distribution (refer to [4]) and Pascal distribution (refer to [1,2,19]). These studies established necessary and sufficient conditions for specific univalent function classes.
Motivated by previous research on the connections between distinct subclasses of analytic univalent functions and hypergeometric, Poisson, and binomial distribution series, we employ the convolution operator and the integral operator to ascertain specific inclusion relations between and with different subclasses of analytic univalent functions. This is how the remainder of the article is organized: We present some preliminary findings related to the several subclasses mentioned above in Section 2. The inclusion properties of the linear operators and associated with the Pascal distribution series function from the class are discussed in Section 3. Our primary focus is on finding sufficient conditions for the operators and . All of the findings are presented with proof in Section 3. As corollaries, several particular cases of the conclusions derived in Section 3 are described in Section 4. Section 5 contains the work’s conclusion and potential next directions.
2. Preliminary Results
Lemma 1
([18]). Let has the form specified in (1), a sufficient condition for Ψ to be in is stated as follows
where , and .
Lemma 2
([19]). Let has the form specified in (1), a sufficient condition for Ψ to be in is stated as follows
where , and .
Lemma 3
([21]). Assume has the form specified in (1), then Ψ will be in if the following inequality holds
where , .
Lemma 4
([21]). Assume has the form specified in (1), then Ψ will be in if the following inequality holds
where , .
Lemma 5
([13]). Let has the form specified in (1), a sufficient condition for Ψ to be in is stated as follows
where and .
Lemma 6
([13]). Let has the form specified in (1), a sufficient condition for Ψ to be in is stated as follows
where and .
Lemma 7
([11]). Assume has the form specified in (1), then Ψ will be in if the following inequality holds
where .
Lemma 8
([12]). Assume has the form specified in (1), then Ψ will be in if the following inequality holds for
Lemma 9
([12]). Assume has the form specified in (1), then Ψ will be in if the following inequality holds for
Lemma 10
([23]). Let has the form specified in (1), a sufficient condition for Ψ to be in is stated as follows
where , .
Lemma 11
([24]). Let has the form specified in (1), a sufficient condition for Ψ to be in is stated as follows
where , .
3. Main Results
This section presents the main findings of our study. We derived conditions for the linear operators such that they would be in different subclasses of univalent functions. The results are analyzed in terms of accuracy which provides valuable insights into their theoretical and practical implications.
3.1. Results on Convolution Operator
In this subsection, we derived inclusion results for the linear operator .
Theorem 1.
Let has the form specified in (1). Suppose Ψ also in and satisfies the following condition
then for and , it follows that .
Proof.
Applying Equation (8) to the sufficient condition for the class as presented in Lemma 1, which gives
Using the hypothesis of the theorem along with Equation (20) completes the proof. □
Theorem 2.
Let has the form specified in (1). Suppose Ψ also in and satisfies the following condition
then for and , it follows that .
Proof.
Applying Equation (8) to the sufficient condition for the class in Lemma 2, which gives
Using the hypothesis of the theorem along with Equation (23) completes the proof. □
Theorem 3.
Let has the form specified in (1). Suppose Ψ also in and satisfies the following condition
then for and , the operator .
Proof.
Applying Equation (8) in Lemma 3, which gives
Using the hypothesis of the theorem along with Equation (26) completes the proof. □
Theorem 4.
Let has the form specified in (1). Suppose Ψ also in and satisfies the following condition
then for and , the operator .
Proof.
Applying Equation (8) in Lemma 4, which gives
Using the hypothesis of the theorem along with Equation (29) completes the proof. □
Theorem 5.
Let has the form specified in (1). Suppose Ψ also in and satisfies the following condition
then for and , it follows that .
Proof.
Applying Equation (8) to the sufficient condition for the class in Lemma 5, which gives
We attain the desired outcome by employing Equation (33) together with the theorem’s hypothesis. □
Theorem 6.
Let has the form specified in (1). Suppose Ψ also in and satisfies the following condition
then for and , it follows that .
Proof.
Applying Equation (8) to the sufficient condition for the class in Lemma 6, which gives
We attain the desired outcome by employing Equation (36) together with the theorem’s hypothesis. □
Theorem 7.
Let has the form specified in (1) and assume it also belongs to the class . Suppose the following inequality holds
then, for and it follows that .
Proof.
Applying Equation (8) to the sufficient condition for the class in Lemma 7, which gives
Using the hypothesis of the theorem along with Equation (39) completes the proof. □
Theorem 8.
Let has the form specified in (1) and assume it also belongs to the class . Suppose the following inequality holds
then, for and it follows that .
Proof.
Applying Equation (8) to the sufficient condition for the class in Lemma 8, which gives
Using the hypothesis of the theorem along with Equation (42) completes the proof. □
Theorem 9.
Let has the form specified in (1). Suppose Ψ also in and satisfies the following condition
then, for and , it follows that .
Proof.
Applying Equation (8) in Lemma 9, which gives
Using the hypothesis of the theorem along with Equation (45) completes the proof. □
Theorem 10.
Let has the form specified in (1). Suppose Ψ also in and satisfies the following condition
then, for and , it follows that .
Proof.
Applying Equation (8) to the sufficient condition for the class in Lemma 10, which gives
Using the hypothesis of the theorem along with Equation (48) completes the proof. □
Theorem 11.
Let has the form specified in (1). Suppose Ψ also in and satisfies the following condition
then, for and , it follows that .
Proof.
Applying Equation (8) in Lemma 11, which gives
Using the hypothesis of the theorem along with Equation (51) completes the proof. □
Remark 1.
Note that in Theorem 1 if , and with the condition then the linear operator is starlike function.
3.2. Results on Integral Operator
Let us consider a integral operator defined as
Let then
here
In this subsection, we derived the conditions for the integral operator such that it would be in convex subclasses of univalent functions.
Theorem 12.
Let with the form (1), and assume it also belongs to the class . Suppose the following inequality holds
then, for and , it follows that .
Proof.
Applying Equation (52) to the sufficient condition for the class in Lemma 2, which gives
Using the hypothesis of the theorem along with Equation (55) completes the proof. □
Theorem 13.
Let with the form (1), and assume it also belongs to the class . Suppose the following inequality holds
then, for and , it follows that .
Proof.
Applying Equation (52) in Lemma 4, which gives
Using the hypothesis of the theorem along with Equation (58) completes the proof. □
Theorem 14.
Let with the form (1), and assume it also belongs to the class . Suppose the following inequality holds
then, for and , it follows that .
Proof.
The sufficient condition for the class in Lemma 6 gives
Using the hypothesis of the theorem along with Equation (62) completes the proof. □
Theorem 15.
Let with the form (1), and assume it also belongs to the class . Suppose the following inequality holds
then, for and , it follows that .
Proof.
Applying Equation (52) to the sufficient condition for the class in Lemma 9, which gives
Using the hypothesis of the theorem along with Equation (65) completes the proof. □
Theorem 16.
Let with the form (1), and assume it also belongs to the class . Suppose the following inequality holds
then, for and , it follows that .
Proof.
Applying Equation (52) in Lemma 11, which gives
Using the hypothesis of the theorem along with Equation (68) completes the proof. □
Remark 2.
Observe that the sufficient conditions for the integral operator , as outlined in Theorem 12, 13, 14, 15 and 16, align perfectly with those specified in Theorem 1, 3, 5, 8 and 10, respectively, thus ensuring the corresponding validity of the convolution operator .
4. Special Cases
In this section, we present some corollaries, which are derived directly from the theorems in Section 3.
4.1. Corollaries for Convolution Operator
In this subsection we derived corollaries for the linear operator .
If we take in Theorem 1 and Theorem 2, we obtain the following results directly.
Corollary 1.
Let with the form (1), and assume it also belongs to the class . Suppose the following inequality holds
then for and , it follows that .
Corollary 2.
Let has the form specified in (1) and assume it also belongs to the class . Suppose the following inequality holds
then for and , it follows that .
Corollary 3.
Let has the form specified in (1) and assume it also belongs to the class . Suppose the following inequality holds
then for and , it follows that .
Corollary 4.
Let has the form specified in (1) and assume it also belongs to the class . Suppose the following inequality holds
then for and , it follows that .
Corollary 5.
Let has the form specified in (1) and assume it also belongs to the class . Suppose the following inequality holds
then for and , it follows that .
Corollary 6.
Let has the form specified in (1) and assume it also belongs to the class . Suppose the following inequality holds
then for and , it follows that .
Corollary 7.
Let has the form specified in (1) and assume it also belongs to the class . Suppose the following inequality holds
then for and , it follows that .
Corollary 8.
Let has the form specified in (1) and assume it also belongs to the class . Suppose the following inequality holds
then for and , it follows that .
Corollary 9.
Let has the form specified in (1) and assume it also belongs to the class . Suppose the following inequality holds
then for and , it follows that .
Corollary 10.
Let with the form (1), and assume it also belongs to the class . Suppose the following inequality holds
then for and , it follows that .
4.2. Corollaries for Integral Operator
In this subsection we derived corollaries for the linear operator .
If we take in Theorem 12, we obtain the following result directly.
Corollary 11.
Let has the form specified in (1) and assume it also belongs to the class . Suppose the following inequality holds
then for and , it follows that .
Corollary 12.
Let has the form specified in (1) and assume it also belongs to the class . Suppose the following inequality holds
then for and , it follows that .
Corollary 13.
Let has the form specified in (1) and assume it also belongs to the class . Suppose the following inequality holds
then for and , it follows that .
Corollary 14.
Let has the form specified in (1) and assume it also belongs to the class . Suppose the following inequality holds
then for and , it follows that .
Corollary 15.
Let with the form (1), and assume it also belongs to the class . Suppose the following inequality holds
then for and , it follows that .
Remark 3.
Observe that the conditions for the linear operator , as outlined in Corollary 11, 12, 13, 14 and 15, align perfectly with those specified in Corollary 1, 3, 5, 7 and 9, respectively, thus ensuring the corresponding validity of the linear operator .
5. Conclusions
This study presents significant results on the inclusion properties of and for a certain class of normalized analytic functions. Using the coefficient bounds of the functions in the class , we determined the sufficient conditions for the linear operators. These findings help to determine the geometric properties of linear operators generated by functions from subclasses of analytic functions, which play a significant role in geometric function theory.
Future research is on finding sharp conditions for these results and exploring different linear operators generated by special functions and functions from subclasses of analytic functions. This study is the foundation for further studies that offer new possibilities for theoretical and practical applications.
Problem 1.
Determine sufficient conditions for the integral operator to belong to the classes , , , and .
Author Contributions
Conceptualization, S.R.M., M.K.G. and R.K.; methodology, S.R.M., M.K.G. and R.K.; validation, S.R.M. and R.K.; formal analysis, M.K.G.; writing—original draft preparation, M.K.G.; writing—review and editing, S.R.M. and R.K.; supervision, R.K.; funding acquisition, S.R.M. All authors have read and agreed to the published version of the manuscript.
Funding
This work was supported by the Deanship of Scientific Research, Vice Presidency for Graduate Studies and Scientific Research, King Faisal University, Saudi Arabia [Grant No. KFU250159].
Data Availability Statement
Data are contained within the article.
Conflicts of Interest
The authors declare no conflicts of interest.
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