Abstract
Using convolution (or Hadamard product), we define the El-Ashwah and Drbuk linear operator, which is a multivalent function in the unit disk , and satisfy its specific relationship to derive the subordination, superordination, and sandwich results for this operator by using properties of subordination and superordination concepts.
MSC:
30C45
1. Introduction and Definitions
The set denotes the class of all analytic functions in the open unit disk and as the subclass of , which consists of the form functions
With as the class of all multivalent functions in open unit disk of the form
Additionally, we use to denote the class of analytic functions in the open unit disk and normalize them with (0) = 0, (0) = 1.
Additionally, consider as the class of the univalent function in ,
Let and be the subclasses of such that:
then is a starlike function;
, then is a convex function;
, then is a close-to-convex function.
If the functions and are analytic in , then we say is subordinate to or f is said to be superordinate to f in , written as or if there is a Schwarz function analytic in , with , so that and . In particular, if the function g is univalent in , then the subordination is equivalent to and , (see [1,2,3,4,5,6,7,8]).
If , where is provided by (1) and is defined by
the Hadamard product (or convolution) of the function is defined by
Let such that and
El-Ashwah and Drbuk [5] introduced the linear operator defined by
It is readily verified from (4) that
Putting in (4), we obtain the Prajapat operator , see [9].
Additionally, when , we obtain the Erdelyi-Kober integral operator , see [10].
Definition 1.
Let:and ( be univalent in . If () is analytic in , that fulfils the second-order differential subordination [11]:
then is the differential subordination solution of (6).
Definition 2.
Let:and(be univalent in. If() andare univalent inandfulfill the second-order differential superordination [11]:
thenis the differential superordination solution of (7).
Definition 3.
Letbe the collections of functionsthat are analytic and injective on, when andfor[11].
Lemma 1.
Letbe the univalent function inand letandbe holomorphic in a domain(with, when (). Set and . Suppose that [12]
is starlike in.
,.
Ifis holomorphic inwith,(, and, then.
Lemma 2.
Letbe convex inandwith. Ifis holomorphic inandthen[11].
Lemma 3.
Letbe convex univalent inand letandbe holomorphic in a domain, (. Suppose that [12]
is starlike univalent in.
,.
If, with (, is univalent in and , then .
Lemma 4.
Letbe convex inand.
If,is univalent inand, then[12].
2. Subordination Results
Theorem 1.
Letbe convex univalent in, with, and suppose
If, it satisfies the subordination:
then
Proof.
Consider
Then
We have
By using (5) we obtain
and
By using the hypothesis, we obtain .
Additionally, apply Lemma 2, when and , then
□
Corollary 1.
Letbe convex univalent in, with, and suppose
If, it satisfies the subordination:
then
Theorem 2.
Letbe convex univalent in,, andfor all, and suppose thatsatisfies:
where, and. Suppose thatis a starlike univalent in.
Ifsatisfies the subordination:
where
then
Proof.
Let and , , when and are analytic in . □
Then, we obtain and .
Since is starlike, then is starlike in and
.
Additionally, consider
Then,
We obtain
Since
That
From (8) we obtain and using Lemma 1 we obtain
Corollary 2.
Letbe convex univalent in,, andfor all, and suppose thatsatisfies:
whereand.
Suppose thatis a starlike univalent in.
If, it satisfies the subordination:
then
3. Superordination Results
Theorem 3.
Letbe convex in, with, , , if,
and
is univalent inand satisfies the superordination.
then
Proof.
Consider
then
We have
with the same steps of Theorem 1 and using the hypothesis, we obtain
Apply Lemma 4 we obtain
□
Corollary 3.
Letbe convex in, with, , , if,
and
is univalent inand satisfies the superordination
then
Theorem 4.
Letbe convex univalent inandfor alland suppose thatsatisfies:
where,, , andare all starlike univalent in.
If, satisfies the condition:
andis univalent in.
If, then
Proof.
Let and , , when is analytic in and is analytic in . Then, we obtain . □
Since is starlike, then is starlike in and
Now, let
From (8) we obtain
Using Lemma 3 we obtain
Corollary 4.
Letbe convex univalent in U,, andfor alland suppose thatsatisfies:
where,, , andare starlike univalent in.
Let, satisfies the condition:
andis univalent in.
If, then
4. Sandwich Results
By combining the above theories, we obtain the following two sandwich theories.
Theorem 5.
Letbe convex univalent in, withand
where.
Ifand
and
is univalent in, it satisfies:
then.
Theorem 6.
Letbe convex univalent in, with, and letsatisfy the condition:
andis univalent in.
If
then
5. Conclusions
In this paper, using the convolution (or Hadamard product) we defined the El-Ashwah and Drbuk linear operator, which is a multivalent function in the unit disk U and satisfied its specific relationship to derive the subordination, superordination, and some sandwich results for this operator using the properties of subordination and superordination concepts. The interesting results can be obtained for other operators using the same techniques of subordinations and superordinations.
Author Contributions
Conceptualization, L.-I.C. and A.R.S.J. methodology, L.-I.C. and A.R.S.J. software, L.-I.C. and A.R.S.J.; validation, L.-I.C. and A.R.S.J.; formal analysis, L.-I.C. and A.R.S.J.; investigation, L.-I.C. and A.R.S.J.; resources, L.-I.C. and A.R.S.J.; data curation, L.-I.C. and A.R.S.J.; writing—original draft preparation, L.-I.C. and A.R.S.J.; writing—review and editing, L.-I.C. and A.R.S.J.; visualization, L.-I.C. and A.R.S.J.; supervision, L.-I.C. and A.R.S.J.; project administration, L.-I.C. and A.R.S.J.; funding acquisition, L.-I.C. 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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