Abstract
In this article, a new linear extended multiplier operator is defined utilizing the q-Choi–Saigo–Srivastava operator and the q-derivative. Two generalized subclasses of q—uniformly convex and starlike functions of order —are defined and studied using this new operator. Necessary conditions are derived for functions to belong in each of the two subclasses, and subordination theorems involving the Hadamard product of such particular functions are stated and proven. As applications of those findings using specific values for the parameters of the new subclasses, associated corollaries are provided. Additionally, examples are created to demonstrate the conclusions’ applicability in relation to the functions from the newly introduced subclasses.
Keywords:
subordination; uniformly starlike function; uniformly convex function; convolution (Hadamard) product; subordinating factor sequence; q-derivative operator; q-Choi–Saigo– Srivastava operator MSC:
30C45; 30A10
1. Introduction
The outcome of this work is connected to geometric function theory, and techniques based on subordination are utilized to obtain those results, combined with aspects regarding q-calculus operators.
Let the class denoted by contain all functions of the form
where .
As given in [,,], if f and ℏ are analytic in U, f is subordinate to ℏ, denoted as , if there exists an analytic function , with and for all , such that , . In the case when the function ℏ is univalent in U, is interpreted as:
If a function satisfies
then f is said to be starlike of order δ, written as , where denotes the class of all such functions.
If the function has the property
then f is said to be convex of order δ, written as , where denotes the class of all such functions.
For = 0, = and = K refer to the regular classes of starlike and convex functions in U, respectively.
In [], was designated to represent the class of uniformly convex functions of order δ and type ρ containing all functions satisfying:
where , and .
Similarly, represents the class of all functions satisfying:
where , and .
If follows that iff . We emphasize that these classes generalize other various subclasses defined by several authors, and for , we obtain the classes and , respectively.
- (i)
- Thus, the class of uniformly convex functions, , was investigated by Goodman and has an interesting geometric property (see []).
- (ii)
- The class was defined by Rønning in [], while the classes and were introduced and investigated by Rønning in [].
- (iii)
- For , the classes and were defined by Kanas and Wiśniowska in [,], respectively.
The investigation on the q-derivative, which has applications in various branches of mathematics and other related fields, has inspired scholars to use it in geometric function theory, too. Jackson [,] described the q-derivative and the q-integral, and certain incipient applications of those functions can be seen in []. By applying the idea of convolution, Ķanas and Răducanu [] presented the q-analogue of the Ruscheweyh differential operator, obtaining the first characteristics of this new operator. Several types of analytical functions defined by the q-analogue of the Ŕuscheweyh differential operator were investigated by Aldweby and Darus [], Mahmood and Sokol [], and others. Furthermore, q-difference operators were investigated in [,,]; fractional calculus aspects were added to the studies regarding q-calculus in [,,]; and a q-integral operator was used for studies in []. The q-Srivastava–Attiya operator is used for investigation on the class of close-to-convex functions in [], and a q-analogue integral operator is applied for a family of non-Bazilevič functions in []. A q-analogue of a multiplier transformation is used for obtaining new differential subordination and superordination results in [].
We will now introduce the fundamental idea of the q-calculus established by Ĵackson [] and useful for our research. Additionally, this technique can be used to higher- dimensional domains.
Definition 1
([,]). The q-derivative, or the Jackson derivative, of a function f is defined by
As a remark, for a function , it follows that
where is the q-bracket of ν; that is,
and
Definition 2
([,]). For and , the q-shifted factorial is defined by
and in terms of basic or q-gamma function
where the q-gamma function is defined by
and
For the q-gamma function, , it is known that
where is defined by (3), and in terms of the classical gamma function , we have .
Wang et al. developed in [], based on the the concept of the convolution and the notion of q-derivative, the q-analogue Choi–Saigo–Srivastava operator ,
where
where stands for the q-generalized Pochhammer symbol for defined by
Thus,
while
Definition 3.
For and , with the aid of the operator , we will define the new linear extended multiplier q-Choi–Saigo–Srivastava operator as follows:
where , , , , and .
Remark 1.
The following operators, which have been investigated by various authors, are obtained by specifying the parameters q, m, α, β, τ, and μ:
- (i)
- For , , , and , the operator was defined and studied by Al-Oboudi [];
- (ii)
- If , , , , and , the operator was introduced by Sălăgean [];
- (iii)
- Taking , , and , the operator was studied Cătaş [];
- (iv)
- Considering , , and , the operator was introduced and studied by Aouf et al. [];
- (v)
- For , , , and , the operator was studied by Govindaraj and Sivasubramanian [];
- (vi)
- If , the operator was defined and studied by El-Ashwah et al. [] for , , , , ;
- (vii)
- Taking , , , and , the operator , , was studied by Cho and Srivastava [];
- (viii)
- Considering , and , the operator was defined and investigated by Wang et al. [];
- (ix)
- For , , , and , the operator was introduced and studied by Al-Oboudi and Al-Amoudi [];
- (x)
- If we take and , we obtain the operator studied by Kota and El-Ashwah [];
- (xi)
- Taking , , and , the q-analogue integral operator of Noor was defined and studied in [];
- (xii)
- Considering , , , and , the differential operator was studied in [,];
- (xiii)
- For , , , , and , the Owa–Srivastava operator was introduced and investigated in [].
Implementing the linear multiplier q-derivative operator provided by (6), for , , , , , , and , new subclasses of q—uniformly convex functions of order δ in U, and of q—uniformly starlike functions of order δ in U are introduced as follows:
Definition 4.
A function belongs to if:
and belongs to if:
Remark 2.
(i) and
and
(ii) and
and
(iii) and
and
(iv) and
and
(v) and
and
where
(vi) and
and
where
(vii) and
and
where
The following definition and lemma are required to demonstrate our original results.
Definition 5
([], p. 690, (Subordinating factor sequence)). A sequence of complex numbers is called a subordinating factor sequence if, whenever f of the Form (1) is convex (univalent) in U, the following subordination holds:
Lemma 1
([], Theorem 2, p. 690). The sequence is a subordinating factor sequence if and only if
The first new outcome, obtained using the operator given by (6) and the related results, presents conditions for a function to belong to the newly introduced class . This first proven theorem is followed by a corollary stating the conditions for a function to be in the class . An example shows that the classes are not empty. A subordination result involving the convolution product of functions from class is described in Theorem 2. It is highlighted that this result generalizes known results, and the following corollary proves similar subordination results regarding the class . An example accompanies the proved results employing the technique used earlier by Attiya [], Srivastava and Attiya [], and Singh []. Some special cases of this operator are also obtained by Aouf and Mostafa [] and Frasin [].
2. Main Results
Unless explicitly stated, it will be presumed throughout this article that , , , , , and .
Our initial finding provides a sufficient condition such that the function to be considered a member of the class .
Theorem 1.
If a function satisfies the following inequalities:
then .
Proof.
For the proof of the assertions of the theorem, it is necessary to show that the following inequality, equivalent to (9), holds:
By virtue of (10) and Theorem 1, the subsequent sufficient condition for the function to be included in the class is shown.
Corollary 1.
Proof.
Therefore, if the assumptions of this theorem hold, according to Theorem 1 it follows that . According to the equivalence (10), we conclude that . □
For the particular case , , the above two results reduce to the next examples:
Example 1.
1. If
then , .
2. If
then , .
Remark 3.
Replacing in the assumptions of the Theorem 1 and of the Corollary 1 the values
we obtain sufficient conditions for the functions
to be members of the classes , and , respectively.
Based on the implications of Theorem 1 and Corollary 1, we define the subclasses and , which consist of functions whose coefficients meet the requirements (12) and (13), respectively.
Certain subordination results for the functions in classes and are provided in the next theorem by applying the techniques previously used by Attiya [], Srivastava and Attiya [], and Singh [].
Theorem 2.
If the function is a member of the class , then for all , we have
and
The above constant is the best estimate.
Proof.
If , and is an arbitrary function of the class K, then
Thus, by Definition 3, the claim of the theorem is true if the sequence
is a subordination factor sequence, with . According to Lemma 1, the following equivalent relation must be proven:
Now,
Thus, (17) holds true in U. The proof of (14) follows by considering in (13). Next, choosing the function given by
and by using (13), we have
It can be easily verified that
then the constant is the best possible. The theorem’s proof is now complete. □
Remark 4.
Employing and in Theorem 2, the results previously obtained by Aouf and Mostafa ([], Theorem 2.4); are found.
Similarly, we can demonstrate the following corollary by using (10) and Theorem 2.
Corollary 2.
Consider the function from the class . In this case, the following relation is true:
and
The constant is the best estimate.
Putting and in Theorem 2, the subsequent corollary emerges.
Corollary 3.
Consider the function a member of the class . The following subordination is satisfied:
and
The constant is the best estimate.
Putting and in Theorem 2, the next corollary can be stated.
Corollary 4.
Let the function be in the class . Then
and
The constant is the best estimate.
Employing and in Corollary 4, we obtain the following particular case as an example.
Example 2.
The constant is the best estimate.
(ii) For in (i) then
and
The constant is the best estimate.
Remark 5.
Letting and in Corollary 2, we have the results proved by Frasin ([], Corollaries, 2.5).
3. Conclusions
This study employs means of q-operators combined with differential subordination techniques and the notion of convolution. A new linear extended multiplier q-Choi–Saigo–Srivastava operator in the open unit disk U is introduced in Definition 3. This operator is used for introducing and investigating the subclasses of normalized analytic functions presented in Definition 4, and . Subordination results involving the Hadamard product of the associated functions are established in two theorems. Interesting corollaries and particular cases are shown for each of those theorems for particular choices of parameters found in the definition of the classes. Examples are also associated with the theorems to highlight the relevance of the new results.
In future investigations, the new linear extended multiplier q-Choi–Saigo–Srivastava given in Definition 3 can be applied for further developments in the theories of differential subordination and its dual, differential superordination introduced by Miller and Mocanu in 2003 [] as performed in [,]. The newer theories of strong differential subordination and superordination can be considered for investigations involving the new operator, as presented in []. In addition, the theories of fuzzy differential subordination and superordination can be applied as was done recently in [,]. The q-operator employed in this study can be used for defining other subclasses of analytic functions as it has been done for -convex functions in [] or for multivalent functions in [].
Author Contributions
Conceptualization, E.E.A. and G.I.O.; methodology, E.E.A. and A.M.A.; validation, G.I.O., S.A.S. and E.E.A.; formal analysis, S.A.S., A.M.A. and G.I.O.; investigation, E.E.A., A.M.A. and S.A.S.; writing–original draft preparation, E.E.A., A.M.A. and S.A.S.; writing–review and editing, G.I.O., S.A.S. and E.E.A.; supervision, G.I.O. and E.E.A. All authors have read and agreed to the published version of the manuscript.
Funding
This research received no external funding.
Data Availability Statement
Not applicable.
Conflicts of Interest
The authors declare no conflict of interest.
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