Abstract
This paper examines two subclasses of multivalent analytic functions defined with higher-order derivatives. These classes of functions are generalizations of several known subclasses that have been studied in separate works. Moreover, we find several interesting results for functions in these classes, including subordination results, containment relations, and integral preserving properties.
Keywords:
higher-order derivatives; multivalent functions; α-convex functions; α-close to convex; n-symmetrical points MSC:
30C45; 30C55
1. Introduction
Let denote the family of analytic functions be defined in the open unit disc of the complex plane with the following form:
where Additionally, let If there exists a Schwarz function analytic in with and , such that then we say that the function is subordinate to in , expressed as (or simply ). The subordination is identical to and if the function g is univalent in A function is said to be in the class if it satisfies the inequality
where , , and Additionally, A function is said to be in the class if it satisfies the following inequality
The classes and were introduced and studied by Nunokawa [1] and Srivastava et al. [2] (see also [3,4,5,6,7,8,9]). We note that, and where and are the well known families of starlike and convex functions of order respectively, introduced by Robertson [10]. It is assumed in the sequel that is an analytic and convex function with a positive real part in the open unit disc , satisfies and is symmetrical with respect to the real axis. In [11], Ali et al. defined the classes and consist, respectively, of Ma–Minda type starlike and convex -valent functions with higher-order derivatives given by
and
Here, we introduce the class , which unifies the classes and as follows:
Definition 1.
Denote by the family of functions satisfying the following condition
Remark 1.
- , and ,
- (see Wang et al. [12]),
- where is the class of β-starlike functions introduced by Pascu and Podaru [13].
A function is said to be starlike with respect to symmetrical points in if it satisfies,
Sakaguchi [14] introduced and studied this class. In addition, Shanmugam et al. [15], Lashin [16], Khan et al. [17], and Mahmood et al. [18] have studied some related classes.
For a given positive integer let
Let be the class of functions satisfying
Also, let be the class of functions satisfying
The classes of p-valent starlike functions with respect to n-symmetric points and of p-valent convex functions with respect to n-symmetric points were recently introduced and studied by Ali et al. [19]. Moreover, the classes and , which were studied by Miller and Mocanu ([20] page 314) and Wang et al. [21]. Following them, many authors discussed these classes and its subclasses (see [22,23,24,25,26,27,28,29,30,31,32]).
The following class unifies the two above classes and .
Definition 2.
Let be the family of functions defined by (5). By we denote the family of functions satisfying
Remark 2.
With the appropriate selection of and φ in Definition 2, the following known subclasses are obtained.
- and
- and
- The class is equivalent to the class of -starlike functions with respect to n-symmetric points introduced by Paravatham and Radha [33],
- If we put and then is equivalent to the class of starlike functions with respect to the symmetrical points introduced by Sakaguchi [14].
Definition 3.
A function is said to be α-close to convex of higher order with respect to n- symmetric points if it satisfies,
where with . We denote this class by .
Using techniques involving differential subordination, we examine some interesting subordination criteria and inclusion relations, as well as integral operators for functions belonging to the class . In addition, we discuss some properties of functions belonging to the class .
2. Preliminary Lemmas and Some Properties of and
The two lemmas below are often used in our subsequent investigations.
Lemma 1
([33]). Let any two complex numbers, and φ be convex and univalent in with and . Also let Q analytic in with and If analytic in then
Lemma 2
([34]). Let any two complex numbers, and φ be convex and univalent in with and If analytic in then
Proposition 1.
Let and . If then
Proof.
Let
then the function h is of the form . By taking the derivatives in the both sides of (7), we obtain
If we apply Lemma 2 with and , then
□
Proposition 2.
Let and . Also let and
If then
3. Main Results
Throughout this section, inclusion relations for functions in classes and are obtained. Bernardi integral operator is also discussed.
Theorem 1.
Let the function belongs to the class, then the function defined by equality (5) belongs to the class Further, if and then
Proof.
From the definition of , we have
Since if we change z by in (11) where then the left side of (11) is equivalent to
where The following identities are immediately derived from the definition (5) of
Using (13), (12) becomes
By taking the summation relation to from 0 to , we find
Since then each the terms in the left-hand side of Equation (14) is subordinate to Therefore, there exists in such that
Since is convex, we have and so . Since , it follows from Proposition 1 that □
Theorem 2 below shows that
Theorem 2.
Let with . If belongs to the class then we have
Proof.
Let belongs to the class , and let
then Theorem 1 gives It is easy to obtain that
Since then we have
If we apply Lemma 1, we get
which implies , and this completes the proof. □
Remark 3.
- Putting and in Theorem 2, we get the result obtained by Wang et al. [12].
- Putting and in Theorem 2, we get the result obtained by Wang et al. [21].
- Putting and in Theorem 2, we obtain the result obtained by Parvatham and Radha [33].
Theorem 3.
Let and , also, let ξ given by Equation (8) . If then
Proof.
Take into account the definition of given by Equation (5) with instead of . Hence, it is obvious that Differentiating this equation with respect to z, we have
Differentiating (15) k times we get
Also, from (8) we get
Considering that then, by applying the first section of Theorem 1 when we obt ain Then, Proposition 2 gives or equivalently,
If we let
and
then, both the functions h and Q are analytic in such that and Differentiating (17) and using (19), we obtain
On using (16), we see that
Based on Lemma 1, we have , which ends the proof. □
Theorem 4.
Let . Then, we have
Proof.
Let . Setting
we obtain
Theorem 1 gives us because . Lemma 1 is once more applied to produce , proving Theorem 4. □
Remark 4.
Putting and in Theorem 4, we reach the result obtained by Parvatham and Radha [33].
4. Conclusions
Analytic p-valent functions were recently studied using higher-order derivatives. With the higher-order derivatives, we defined two subclasses of analytic p-valent functions with n-symmetric points, which unify the previously introduced and studied subclasses. This paper aims to present several exciting subordination results, containment relations, and integral preserving properties for functions in these classes. Some of our results extend previously known results and some of our results are new. This work can be extended to the classes of harmonic multivalent n-symmetric and meromorphic multivalent n-symmetric type functions involving quantum calculus, as discussed in [35,36,37,38,39].
Author Contributions
Conceptualization, A.M.Y.L. and F.Z.E.-E.; Methodology, F.Z.E.-E.; Investigation, A.M.Y.L.; Writing—original draft, F.Z.E.-E.; Writing—review and editing, A.M.Y.L. and F.Z.E.-E.; Project administration, A.M.Y.L.; Funding acquisition, A.M.Y.L. All authors have read and agreed to the published version of the manuscript.
Funding
This research work was funded by institutional Fund Projects under grant no. (IFPIP:128-130-1443), provided by the Ministry of Education and King Abdulaziz University, DSR, Jeddah, Saudi Arabia.
Data Availability Statement
Data sharing not applicable.
Acknowledgments
This research work was funded by institutional Fund Projects under grant no. (IFPIP:128-130-1443). The authors gratefully acknowledge technical and financial support provided by the Ministry of Education and King Abdulaziz University, DSR, Jeddah, Saudi Arabia. Also, the authors would like to express their thanks to the referees for their helpful comments and suggestions, which improved the presentation of the paper.
Conflicts of Interest
The authors declare no conflict of interest.
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