1. Introduction
Let
be a positive integer and let
be a complex number. Suppose that
represents the collection of analytic functions within the open unit disk
that can be written as follows:
Let
denote the class of all multivalent analytic functions in the open unit disk
and have the form
where
Consider two analytic functions
and
defined on
We describe
as subordinate to
or
is a superordinate to
in such a case we write
if there exists an analytic function
in
as well as
and
such that
(see [
1]). For a univalent function
, the subordination relation
holds precisely when
and the image of
under
is contained in the image of
under
.
The Borel distribution (BD), described by the probability mass function presented below, was studied by Wanas and Khuttar [
2] in a recent work.
In [
2], Wanas and Khuttar described a series in which the coefficients are given by the probability values of the Borel distribution (BD)
where
and
We examine the operator
defined via inversion or Hadamard product
where
The Borel distribution is characterized by the parameter , which determines the coefficients of the Borel distribution series used in this study. These coefficients are incorporated into a linear operator through the Hadamard product, allowing probabilistic concepts to be applied in geometric function theory.
The class
consists of analytic multivalent functions in the open unit disk, represented by
This class generalizes the well-known class of univalent functions, since the case
reduces to the univalent case.
The linear operator introduced in the paper is defined by convolution with the Borel distribution series. It transforms multivalent analytic functions while preserving analyticity and serves as the main tool for establishing differential subordination, superordination, and sandwich-type results.
Example 1. Let be defined byApplying the operator with , we obtainWe compute the coefficients explicitly. For , we haveand for ,Thus,It is evident that the operator reduces the magnitude of the higher-order coefficients by exponentially decaying factors. In particular, the coefficients of and decrease from and to and , espectively. Consequently, the influence of higher-order terms is diminished, resulting in a smoother analytic behavior of the transformed function. This effect is illustrated graphically in Figure 1, where the image of the unit disk under appears less distorted compared to that of . Moreover, the parameter controls the rate of decay and hence determines the strength of this transformation. Consider as the collection consisting of all univalent functions on the boundary of excluding the set , where , and .
Therefore,
Figure 1 confirms the geometric smoothing effect of the proposed operator.
Overall, this example demonstrates that the proposed operator is not merely an algebraic transformation of coefficients. Rather, it acts as an effective geometric smoothing operator that systematically suppresses the influence of higher-order terms through exponentially decaying weights. This property makes it particularly useful in the investigation of coefficient estimates, geometric function theory, differential subordinations, and related inclusion relationships among subclasses of analytic functions.
Definition 1 ([
1])
. Suppose that , belong to and belong to . The family of admissible functions, denoted by , comprises those mappyings that satisfy the admissibility requirement defined bywhenever the following conditions are simultaneously met:where with . We simply write .
In the special case where , with and , it follows that and . Accordingly, we established in this instance, as well as in more unique situations where ,; the class is represented by .
Definition 2 ([
3])
. Suppose that with belong to the set as well as The admissible mappings family, represented by , comprises those mappings. that satisfy the admissibility requirement defined byif all of the following conditions are simultaneously met:where , and . Specifically, the family is written as Lemma 1 ([
1])
. Letting represent the family of functions , as well as Ifbe an analytic function satisfies the conditionthen Lemma 2 ([
3])
. Letting represent the family of functions , as well as If with be an analytic and injective in thenimplies This study focuses on the differential subordination and superordination of multivalent functions related to the linear operator
described by Borel distribution. Recently, numerous authors have examined subordination and superordination for analytic functions defined via certain operators. In [
4], Aouf at al. used generalized differential operator and investigated some differential subordination and superordination results of higher-order derivatives of multivalent functions. Rahrovi [
5] obtained subordination and superordination properties for convolution operator. In 2017, Attiya and Yassen [
6] discussed some subordination and superordination results associated with generalized Srivastava-Attiya operator, while in 2021 Morais and Zayed [
7] introduced applications of differential subordination and superordination theorems for fluid mechanics. Alhwikem et al. [
8] presented and examined a certain families of admissible functions associated with fuzzy differential subordination. Also, some related findings are shown in [
9,
10,
11,
12].
Lemma 3. Assume that and the linear operator is defined by (2). Thenwhere Proof. Applying (3), we obtain
which establishes the identity
. □
The connection of the present work with Symmetry arises from the invariance properties of the considered classes of multivalent analytic functions under analytic transformations in the unit disk. The proposed Borel-distribution-based linear operator preserves the analytic structure of functions and generates subclasses characterized through differential subordination and superordination. These subclasses exhibit geometric symmetry through their invariant behavior under conformal mappings and admissibility conditions. Therefore, the obtained results contribute to the study of symmetry-type structures in geometric function theory by establishing invariant relationships between analytic functions and their associated operators.
2. Results of Subordination for the Operator
Definition 3. Consider a be a subset of and belongs to The admissibility class, denoted by , consists of those mappings consists of those elements that obey the following admission requirement:whenever the following conditions are simultaneously met:andwhere , as well as .
Theorem 1. Consider . If fulfillthen Proof. Let
be an analytic function in
expressed in the form
thus, by differentiating (5) with regard to
and applying the connection in (3), we obtain
Further computations show that
Specify the transformations from
to
by
By Lemma 1 and Equations (5)–(9), we obtain
Therefore, (4) takes the form
Note that
Thus, the acceptance conditions for both
and
where
belongs to the class
coincide with the admissibility condition stated in Definition 1. Consequently,
qualifies as an element of
This is consistent with the result presented in Lemma 1.
When
constitutes a simply connected domain. In this instance,
for a specific conformal projection
of
upon
, as well as denote the class
as
. Consequently, we derive an extra assumption from the aforementioned theorem. □
Theorem 2. Assume that . If and fulfillswhere , Then, the subordination relationholds. In order to investigate the unspecified behavior of on the boundary of the unit disk , the following corollary offers an explanatory demonstration. Corollary 1. Letting belong to for a certain inside the interval where . Let be analytic and univalent (injective) on the unit disk satisfying and let Suppose further that belongs to the class and that the following condition holds:where , then Proof. From Theorem 1, it follows that
, based on the fact that
Thus,
. □
Theorem 3. Let and be two univalent (injective) functions on the unit disk , with as well as , . Suppose the function satisfies either of the following conditions:
(1) is an element of the class , for some
(2) There exists some such that for every the inclusion holds, and additionally belongs to satisfy Equation (11).
Then, under either condition, we have the subordination relation
Proof.
. Applying Theorem 1 yields
, since
it follows that
. Let us set
and define
, then
According to Lemma 1, if
where
is an arbitrary mapping with
therefore
For
in the interval
taking
, we deduce that
The best dominant for the differential subordination (11) is derived form the following theorem □
Theorem 4. Suppose denotes a function, where is univalent in and is a holds of the followingwhere and complies with at least one of the criteria that follow (1) with ,
(2) is injective in with , and
or
(3) is analytic and injective in as well as there is , where
.
If fulfil the relation in (2.8), thenThus, the best dominant is .
Proof. The conclusions drawn from Theorems 2 and 3 reveal that plays the role of a dominant for (11). In addition, because meets the requirement (12), it also serves as a solution to (11). Consequently, is subordinate to all other dominants, which establishes it as the best possible dominant. □
In the restricted scenario where with and by reference to Definition 1, the collection of admissible functions written as is set forth in the material that follows.
Definition 4. Letting be greater than 0 and be a subset of . The functions that are classified under as admissible functions such thatwhenever , , for all as well as .
Corollary 2. Assume belong to . If belong to and fulfillswhere , thenFor the specific instance where , the family is typically written as Corollary 3. Letting be an element of . If adheres to the inequalitywhere , then Corollary 4. Assume as well as in which casethen Proof. By taking
and
, where
Since
Thus,
is an element of the class
. Consequently, the admissibility condition expressed in (13) is satisfied, and applying Corollary 2 yields the required conclusion. □
Definition 5. Letting taken as an element of Φ in addition to . The admissibility class, denoted by , comprises all mappings that fulfill the admissibility conditionwhenever the following conditions are simultaneously met as follows:andwhere . Theorem 5. Let belong to and . If fulfillswhere Proof. Consider the function
defined as
which is analytic in
By differentiating (16) and utilizing (3), we arrive at the conclusion that
Subsequent calculations indicate that
To bridge the classes of admissible functions, we introduce the mapps
described by:
Let
By using Lemma 1 and Equations (16)–(18) and (20), we obtain
Hence (15), becomes
To conclude the proof, we now demonstrate that the condition governing the admissibility of
belongs to
matches the condition prescribed for
in Definition 1.
It is confirmed that
belongs to
. Accordingly, by virtue of Lemma 1, it follows that
, which is equivalent to the following subordination:
For a simply connected domain
with
is not equal to
. In this instance,
for a certain conformal mapping
of
onto
, and we denote the class
as
. Consequently, we derive the following conclusion from the aforementioned theorem. □
Theorem 6. Consider that . If belongs to and fulfillsthenThe admissibility class, denoted by , consists of those mappings that fulfill the admissibility conditionwhenever the following conditions are simultaneously met: In the particular situation where and by making use of Definition 5, the family of admissible functions written as is presented in what follows.
Definition 6. If as well as be a set. An admissibility class, denoted by , comprises all mappings that fulfill the admissibility conditionwhenever ,, real as well as .
Corollary 5. Assume belong to . If belongs to and fulfillsthenIn the specific setting where , the family is typically written as Corollary 6. Assume belong to . If belongs to and fulfillsthen Corollary 7. If as well as is an element of that fulfillsthen Corollary 8. Assume that as well as belongs to and fulfillsthen Proof. Letting.
As well as
,Because
and for every real
and every
, we getting
. □
Consequently belongs to meaning that the admissibility condition (23) is fulfilled. Then, by applying Corollary 5, we obtain the desired result.
Definition 7. Let be a subset of and let . Consider mapps that are members of the admissible class These functions are required to satisfy the following admissibility condition: under the condition thatands.t .
Theorem 7. Letting belong to and be non-zero. If belongs to and fulfillswhere , then Proof. Specify the function
which remains analytic in
By computing the logarithmic derivative of equation (26) in terms of
and by means of (3), we get
Through logarithmic differentiation of (27) with respect to
and making use of (3), we reach the conclusion that
Next, suppose that transformations taking
to
is defined as
Let
By making use of Lemma 1 along with relations (26), (27), (28), and likewise (30), we deduce
Hence, relation (25) transforms into
Observe that
The admissibility condition imposed on
and on
are precisely those stipulated in Definition 1.1. Accordingly,
is a member of the class
. Applying Lemma 1.1 then yields either the subordination relation,
or the subordination
□
When constitutes a simply linked domain. In this instance, for a certain conformal mapping of D over Ω, and we denote the class as Consequently, we get the following consequence from the aforementioned theorem:
Theorem 8. Consider belongs to the admissible class Furthermore, let be a function that fulfills the subsequent requirements:where , thenIn the specific scenario where , with , The admissible functions , referred to as , is presented below in accordance with Definition 7. Definition 8. Taking to be a set. The collection of admissible mapps denoted by . includes every mapping obeying the following requirement: and for every real and every , we getting .
Corollary 9. Letting belong to . If belongs to and fulfillswhere thenConsider the special instance where Under this circumstance, the class is typically represented as Corollary 10. Letting belong to . If belongs to and fulfillswhere , then Corollary 11. Assume that as well as belong to such thatwhere , then Proof. Assuming that
and
, where
Applying Corollary 9, we have □
3. Superordination Results for the Linear Operator
Herein, we obtain outcomes pertaining to differential superordination problems of the linear operator when applied to analytic functions.
Definition 9. Given and a set s.t we define the admissible class as the collection of functions observing the following admissibility condition:wheneverandwhere , and .
Theorem 9. Letting belong to . If belongs to , then is an element of andis univalent in andwhere , then Proof. Applying (10) together with (34), we obtain the inclusion
In light of the transformation defined in (8), it is clear that the admissibility conditions imposed on
and on
are equivalent to those stated in Definition 2. Thus,
applying Lemma 2, we conclude that either
□
Now assume that not equal is a simply connected set. Under these conditions, can be expressed as for an appropriate conformal map of onto . The notation is then used as an abbreviation for Consequently, from the preceding theorem, we derive the following result:
Theorem 10. Assume that ,. If and is univalent in andwhere , then .
The following conclusion is a corollary derived from the combination of Theorems 2 and 10.
Corollary 12. Consider a univalent function defined on , together with two analytic functions and in . Assume that belongs to with the initial conditions and that is an element of the intersection . Furthermore, suppose that , such thatis univalent in andwhere , then Definition 10. Letting belong to with be a subset of , with not equal to zero. The family of admissible mapps comprises mapps fulfill the admissibility condition.wherewhere and .
We now state the corresponding result that captures the double conclusion of Theorem 3 in the context of differential superordination.
Theorem 11. Given . If simply in , andis univalent in as well aswhere , then Proof. Starting from the results given in (2.18), (3.4), we deduce the inclusion
By applying the function given in relation (2.16) it becomes evident that the admissibility condition for
belongs to
coincides with the admissibility requirement for
as introduced in Definition 1.2. Hence,
belongs to
Applying Lemma 1.2, we obtain the subordination relations
or
□
Suppose next that is a simply connected domain. In this situation can be expressed as for some conformal map of onto the class is then written simply as Therefore, from the preceding theorem, we conclude the following result:
Theorem 12. Suppose that the mapps , is analytic on and . If ,,is holomorphic and injective on andwhere , thenIntegrating the conclusions of Theorems 6 and 12 gives rise to the subsequent essential corollary: Corollary 13. Consider two analytic functions and defined on together with a univalent function on , is an element of with and that lies in the intersection . Furthermore, suppose that , ,is holomorphic and injective on andwhere , thenNow, regarding differential superordination, we obtain the two-sided counterpart of Theorem 7. Definition 11. Letting , as well as be a subset of , with . The set of admissible mapps comprises functions that fulfill the admissibility condition . Wheneverwhere and .
Theorem 13. Letting belong to . If is an element of ,is holomorphic and injective on andwhere , then Proof. We conclude from (2.28) and (3.6) that
The admissibility conditions for
and
, as stated in (30), are equal to those outlined in Definition 2. Therefore,
is an element of
. Consequently, by Lemma 2, we get that
, and therefore
Let us now turn to the case where
is a simply connected domain. In this setting, we may write,
for a specific conformal mapps
of
onto
. Consequently, the admissible class
is denoted more succinctly as
. As a direct consequence of the preceding theorem, we obtain the following result: □
Theorem 14. Consider a function belonging to , is an analytic function defined on . If , ,is holomorphic and injective on andwhere , thenFrom the combination of Theorems 8 and 14, we derive the following sandwich theorem. Corollary 14. Consider a univalent function on , and take with , and be analytic in and . If , ,is univalent in andwhere , then