Abstract
This work is based on the recently introduced concepts of third-order fuzzy differential subordination and its dual, third-order fuzzy differential superordination. In order to obtain the new results that add to the development of the newly initiated lines of research, a new operator is defined here using the concept of convolution and the normalized Lommel function. The methods focusing on the basic concept of admissible function are employed. Hence, the investigation of new third-order fuzzy differential subordination results starts with the definition of the suitable class of admissible functions. The first theorems discuss third-order fuzzy differential subordinations involving the newly introduced operator. The following result shows the conditions needed such that the fuzzy best dominant can be found for a third-order fuzzy differential subordination. Next, dual results are obtained by employing the methods of third-order fuzzy differential superordination based on the same concept of an admissible function. A suitable class of admissible functions is introduced and new third-order fuzzy differential superordinations are obtained, showing how the best subordinant can be obtained under certain restrictions. As a conclusion of this study, sandwhich-type results are derived, linking the outcome of the two dual fuzzy theories.
Keywords:
fuzzy set; third-order fuzzy differential subordination; third-order fuzzy differential superordination; fuzzy dominant; fuzzy best dominant; fuzzy subordinant; best fuzzy subordinant; admissible function; Lommel function MSC:
30C45; 30C80; 26A33; 30C50
1. Introduction
The dual ideas of third-order fuzzy differential subordination and superordination, a recently considered type of fuzzy differential subordination, are the focus of this work. Lotfi A. Zadeh first proposed the idea of the fuzzy set in 1965 [1], which was included into the differential subordination theory leading to the emergence of the fuzzy differential subordination notion in 2012 [2]. The fuzzy differential subordination theory adheres to the general differential subordination idea as investigated in [3,4]. The investigation of fuzzy differential subordination and superordination continues to deliver intriguing results in recent publications. Mittag–Leffler-type distributions are included in the research on the fuzzy differential subordination theory seen in [5,6]. Different types of operators are employed for obtaining the results seen in [7,8]. Quantum calculus operators provide the tools for the new fuzzy differential subordination results obtained in [9,10], and the dual theories of fuzzy differential subordination and superordination are used for developing sandwich-type results involving quantum calculus operators in [11]. All those results involving different types operators, including the ones involving quantum calculus, have motivated the research presented in this paper.
The context for obtaining the innovative conclusions seen in this work was given by the emergence in [12] of the idea of third-order fuzzy differential subordination. Expanding upon the notion put forth in [13], the authors of the work introduced the idea of third-order fuzzy differential subordination. The key notions to be used for the studies pertaining to this line of research for the fuzzy differential subordination theory, including the admissible functions class and basic theorems, were provided in [12], along with the main principles of third-order fuzzy subordination. As the concept of differential superordination was first proposed as a dual idea to that of differential subordination, in light of this concept, the idea of third-order fuzzy differential superordination was first presented in [14], where the dual problem of the third-order fuzzy differential superordination was studied by describing the fundamental ideas connected with the notion of third-order fuzzy differential superordination.
Since no other papers are published so far on the idea of using the two new dual fuzzy theories in order to obtain third-order fuzzy sandwich-type results, the present work adds valuable knowledge for enhancing the new lines of research recently initiated. The framework for the investigation is well known in geometric function theory.
is the class of analytic functions in and , with and .
Certain subclasses of are famous and indispensable for research, such as the following:
where , and
where , and with and .
Designate the class of convex functions as
Furthermore,
Given , if there exists , then is subordinate to , denoted , if , and for every , and . The following is what must be met such that we have the function :
For two functions given by
the convolution of and is defined as
Numerous papers refer to geometric properties of different families of special functions, particularly the generalized hypergeometric functions (see [15,16,17,18]) and the Bessel functions (see [19,20,21,22]). The Lommel functions of the first and second kind appear as specific solutions of particular second-order differential equations in the theory of Bessel functions (see, for example, [23,24,25]). We recall now the Lommel function, denoted by and given by
which is a particular solution of the inhomogeneous Bessel differential equation
where , and stands for the Euler gamma function. It is clear that the function is analytic for all .
Next, the normalized Lommel function is considered as follows:
Using the shifted factorial defined as
the function can be represented by the following series representation:
For simplicity, let and . Thus, the function can be defined as follows:
The function is analytic for all and , and it is clear that .
Using the notions presented above, the new operator used for the investigation is defined by means of a Hadamard product as follows:
Remark 1.
We note that by taking in (6), the operator is obtained, defined as follows:
which is related to Bessel functions of the first kind (see [21]).
The operator , satisfies
and
2. Preliminaries
The new findings in the section that follows will be supported by the subsequent investigations.
Definition 1
([13] (p. 441, Definition 2)). Denote by the set of all functions that are analytic and injective on where
and are such that for . is called the exception set, and the subclass of when can be denoted by and .
From the theory of fuzzy differential subordination, we use the following:
Definition 2
([1]). A fuzzy set comprises of the pair , where ς is a set, , and is a membership function.
Definition 3
([26]). A fuzzy subset of ς is a pair , where is known as the membership function of the fuzzy set and is called fuzzy subset.
The notations that are listed next are used for the investigation proposed here. Let . Indicate by
- (i)
- . Then, , where and .
- (ii)
- If . Then, where and .
Let . We say
and
Definition 4
([26]). Let two fuzzy subsets of η, and . We state that the fuzzy subsets and are equal if , , and we denote by . The fuzzy subset is contained in the fuzzy subset if , and denote by .
Definition 5
([26]). Let and . is fuzzy subordinate to and written as or if each of the following is satisfied:
Definition 6
([13]). Let consider a function where and . Functions , are called admissible functions and belong to the so-called class of admissible functions denoted by if
is satisfied, with
where , and .
In particular, if we set
then
In this case, we set
and, in the special case when the set , the resulting class is simply denoted by .
Definition 7
([14] (Definition 5)). Let Ω be a set in , , . Denote by the set of functions , satisfying
where
with , and . Condition (11) is called the admissibility condition.
The definition of the concept of fuzzy dominance for the solutions of a third-order fuzzy differential subordination is given in [12] in terms of a function that satisfies whenever satisfies
i.e.,
with , and , being called a solution of the fuzzy differential subordination (12). For all dominants of (12), the fuzzy best dominant is a fuzzy dominant satisfying . It is known that the fuzzy best dominant is unique up to a rotation of .
The dual concept of a fuzzy subordinant of a third-order fuzzy differential superordination is introduced in [14] as being a function satisfying or, equivalently written, as , whenever satisfies
i.e.,
with , and , being called a solution for the third-order fuzzy differential superordination (13). For all fuzzy subordinants of (13), the best fuzzy subordinant is a fuzzy subordinant satisfying or, equivalently written, as .
The next two results listed as lemmas, proved in [12] and [14], respectively, serve as tools for obtaining the new outcome of the next sections.
Lemma 1
([12] (Theorem 3.4)). Let with , and consider the function and a function for which
where , and . If Ω is a set in , with satisfying
then
Lemma 2
([14] (Theorem 1)). Let , function given by and , satisfying
where , .
If and are univalent in then
or, equivalently, as
which implies that
In the following sections, by utilizing the third-order differential subordination results in accordance to Antonino and Miller [13] in the unit disk and the third-order fuzzy differential subordination and superordination results introduced by Oros et al. [12,14], we define certain suitable classes of admissible functions and study some third-order fuzzy differential subordination and superordination properties of univalent functions connected with the Lommel function defined by (6). The results obtained using the two dual theories are linked at the end of the study by sandwich-type results.
3. Third-Order Fuzzy Differential Subordination Results
Throughout the study, unless otherwise indicated, we will suppose that .
Certain new third-order fuzzy differential subordinations are obtained in this section. The following definition applies to the class of admissible functions for this purpose:
Definition 8.
Let and . Functions that satisfy
whenever
and
where , and , form the class of admissible functions denoted as .
Our first result is now stated and proved as Theorem 1 below.
Theorem 1.
Consider . If and satisfy
and
then
or
Proof.
Define
Further computations show that
and
Now, we specify how transforms to by
and
Let
Hence, (19) leads to
Accordingly, the admissibility condition in Definition 8 corresponds to the admissibility condition in Definition 6. Thus, by applying (18) and Lemma 1, we write or, equivalently, ,
i.e.,
The proof is completed. □
Example 1.
By taking , in Theorem 1 we obtain
which is analytic in and
then
or
When behaves in an unknown manner on , the following result is generated by Theorem 1.
Corollary 1.
Consider and take with . Consider , for certain when . If and satisfy
and
then
Proof.
Following Theorem 1, we obtain
The assertion of Corollary 1 is obtained from
□
If is a simply connected domain, then for a well-chosen conformal mapping of onto . In this situation, the class is written as . The next listed results are direct outcomes of Theorem 1 and Corollary 1.
Theorem 2.
Corollary 2.
Consider and take with . Consider for certain when . If and satisfy
and
then
The fuzzy best dominant of the fuzzy differential subordination (19) or (34) is obtained by our next theorem.
Theorem 3.
Proof.
In the particular case when and, in view of Definition 8, the class of admissible functions, which we denote by , is described below.
Definition 9.
Let Ω be a set in and . The class of admissible functions consists of the functions such that
whenever , and
Corollary 3.
Let . If , then
If
then
or
where and .
Then, as follows, we define a new admissible class :
Definition 10.
Suppose that Ω is a set in and . The class of admissible functions consists of function which satisfies
whenever
where , and .
Theorem 4.
Consider . If and satisfy
and
then
Proof.
Let
Further computations show that
and
We now specify how transforms to by
and
Let
Hence, (43) leads to
Accordingly, the admissibility condition in Definition 10 corresponds to the admissibility condition in Definition 6. Thus, by applying Lemma 1 and (37), we write or, equivalently, ,
i.e.,
The proof is completed. □
If is a simply connected domain, then for a well-chosen conformal mapping of onto . In this case, the class is written as . The following result is an immediate consequence of Theorem 4.
Corollary 4.
In the particular case when and, in view of Definition 8, the class of admissible functions, which we denote by , is described below.
Definition 11.
Let Ω be a set in and . The class of admissible functions consists of the functions such that
whenever , and
Corollary 5.
Let . If satisfies
If
then
where and .
In the special case when
the class is simply denoted by .
4. Third-Order Fuzzy Differential Superordination Results
We derive certain third-order fuzzy differential superordinations in this section. The following definition applies to the class of admissible functions for this purpose:
Definition 12.
Consider , with and . Functions that satisfy
whenever
where , and , form the class of admissible functions denoted by .
Theorem 5.
Let . If and satisfy
and
is univalent in , then
implies
Proof.
From (27), we deduce that the admissibility condition in Definition 12 corresponds to the admissibility condition for in Definition 8. Therefore, by applying the terms in (48) and Lemma 2, we write
or, equivalently,
The proof is now complete. □
Example 2.
. In Theorem 4, we obtain
which is analytic in and
thus,
or
If is a simply connected domain and for a well-chosen mapping of onto , then . The following theorem is derived from Theorem 5 using procedures similar to those in the previous section.
Theorem 6.
Consider , and λ to be analytic in . If and satisfy the conditions in (48) and
is univalent in , then
implies
For a well-chosen , the next result establishes the existence of the best fuzzy subordinant of (55).
Theorem 7.
Proof.
The proof of Theorem 7 is similar to that of Theorem 3 so we omitted it. □
Next, we consider a new definition for the class of admissible functions, .
Definition 13.
Consider , with and . Functions that satisfy
whenever
where , and , form the class of admissible functions denoted by .
If is a simply connected domain and for a well-chosen conformal mapping of onto , then the class . The following theorem is derived from Theorem 7 using procedures similar to those in the previous section.
Theorem 8.
Proof.
We left out Theorem 8 since its proof is comparable to that of Theorem 4. □
5. Sandwich-Type Results
Two sandwich-type outcomes are shown in this section. Combining Theorems 1 and 5 yields the sandwich-type result that follows:
Theorem 9.
Similarly, combining Theorems 4 and 8, we obtain
Theorem 10.
Remark 2.
By taking in (6), we obtain the operator defined as follows:
which is related to Bessel functions. If this function is used, new results in third-order fuzzy differential subordination can be developed.
6. Conclusions
The theory of differential subordination and superordination advances as a result of the new findings from the inquiry presented in this paper. The basic concepts needed for this study, the Lommel function , and the motivation for the topic’s inquiry are all included in the introduction in Section 1. Section 2 reports the research’s preliminary known results, whereas Section 3 presents the primary findings. The fundamental theorems of the new third-order fuzzy differential subordination theory were established and validated. The findings in Section 4 of this paper contribute to the field of third-order fuzzy differential superordination presenting dual results to those reported in Section 3. Using the previously established new outcome in Section 3 and Section 4, sandwich-type results are stated in Section 5.
The present endeavor provides important knowledge to improve the newly started lines of research because there are currently no published papers on the idea of using the two new dual theories to develop third-order fuzzy sandwich-type outcomes. Also, new results that would enhance our knowledge regarding the topic of third-order fuzzy differential subordination theory could be further developed in view of the statement of Remark 2.
Author Contributions
Conceptualization, E.E.A., G.I.O., R.M.E.-A. and A.M.A.; Methodology, E.E.A., G.I.O., R.M.E.-A. and A.M.A.; Software, E.E.A. and G.I.O.; Validation, E.E.A., G.I.O., R.M.E.-A. and A.M.A.; Formal analysis, E.E.A., G.I.O., R.M.E.-A. and A.M.A.; Investigation, E.E.A., G.I.O., R.M.E.-A. and A.M.A.; Resources, E.E.A., G.I.O., R.M.E.-A. and A.M.A.; Data curation, E.E.A., G.I.O., R.M.E.-A. and A.M.A.; Writing—original draft, E.E.A., G.I.O., R.M.E.-A. and A.M.A.; Writing—review & editing, E.E.A., G.I.O., R.M.E.-A. and A.M.A.; Visualization, E.E.A., G.I.O., R.M.E.-A. and A.M.A.; Supervision, G.I.O.; Project administration, E.E.A.; Funding acquisition, G.I.O. All authors have read and agreed to the published version of the manuscript.
Funding
The publication of this paper was funded by the University of Oradea, Romania.
Data Availability Statement
The original contributions presented in this study are included in the article; further inquiries can be directed to the corresponding author.
Conflicts of Interest
The authors declare no conflicts of interest.
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