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Citation: Oros, G.I.; Oros, G.; Rus,
A.M. Applications of Confluent
Hypergeometric Function in Strong
Superordination Theory. Axioms 2022,
11, 209. https://doi.org/10.3390/
axioms11050209
Academic Editor: Sidney A. Morris
Received: 18 April 2022
Accepted: 21 April 2022
Published: 29 April 2022
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4.0/).
axioms
Article
Applications of Confluent Hypergeometric Function in StrongSuperordination TheoryGeorgia Irina Oros 1 , Gheorghe Oros 1 and Ancut,a Maria Rus 2,*
1 Department of Mathematics and Computer Science, Faculty of Informatics and Sciences,University of Oradea, 410087 Oradea, Romania; [email protected] (G.I.O.);[email protected] (G.O.)
2 Doctoral School of Engineering Sciences, University of Oradea, 410087 Oradea, Romania* Correspondence: [email protected]
Abstract: In the research presented in this paper, confluent hypergeometric function is embeddedin the theory of strong differential superordinations. In order to proceed with the study, the formof the confluent hypergeometric function is adapted taking into consideration certain classes ofanalytic functions depending on an extra parameter previously introduced related to the theory ofstrong differential subordination and superordination. Operators previously defined using confluenthypergeometric function, namely KummerโBernardi and KummerโLibera integral operators, arealso adapted to those classes and strong differential superordinations are obtained for which they arethe best subordinants. Similar results are obtained regarding the derivatives of the operators. Theexamples presented at the end of the study are proof of the applicability of the original results.
Keywords: analytic function; starlike function; convex function; strong differential superordination;best subordinant; confluent (Kummer) hypergeometric function
1. Introduction
The theory of strong differential subordination was initiated by Antonino and Roma-guera [1] as a generalization of the classical concept of differential subordination introducedby Miller and Mocanu [2,3]. The results obtained by Antonino and Romaguera for thecase of strong BriotโBouquet differential subordinations inspired the development of thegeneral theory related to strong differential subordination as seen for the classical case ofdifferential subordination which is synthetized in [4]. The main aspects of strong differen-tial subordination theory were established in a paper published in 2009 [5] by stating thethree problems on which the theory is based on and by defining the notions of solution of astrong differential subordination and dominant of the solutions of the strong differentialsubordination. The class of admissible functions, a basic tool in the study of strong differ-ential subordinations, was also introduced in this paper. The theory developed rapidlyespecially through studies associated to different operators like LiuโSrivastava operator [6],a generalized operator [7], multiplier transformation [8,9], Komatu integral operator [10],Sฤlฤgean operator and Ruscheweyh derivative [11] or a certain differential operator [12].The topic is still interesting for researchers as it is obvious from the numerous publicationsin the last two years when multiplier transformation and Ruscheweyh derivative [13] orintegral operators [14] were used for obtaining new strong subordination results. We canrefer to [15,16] for applications of differential operators in the analyses of phenomena frommathematical biology.
The dual notion of strong differential superordination was introduced also in 2009 [17]following the pattern set by Miller and Mocanu for the classical notion of differentialsuperordination [18]. The special case of first order strong differential superordinationswas next investigated [19]. Strong differential superodinations were applied to a generalequation [20] and they were also related to different operators such as generalized Sฤlฤgean
Axioms 2022, 11, 209. https://doi.org/10.3390/axioms11050209 https://www.mdpi.com/journal/axioms
Axioms 2022, 11, 209 2 of 13
and Ruscheweyh operators [21], new generalized derivative operator [22], or certain generaloperators [23]. This notion is still popular as it can be proved by listing a few more papersthan already shown, published recently [24โ26].
In 2012 [27], some interesting new classes were introduced related to the theoryof strong differential subordination and superordination. They are intensely used forobtaining new results ever since they were connected to the studies.
The study presented in this paper uses those classes which we list as follows:For U = z โ C : |z| < 1 the unit disc of the complex plane, there are some notations
used: U = z โ C : |z| โค 1 and โU = z โ C : |z| = 1. H(U) denotes the class ofholomorphic functions in the unit disc.
Let H(U รU
)denote the class of analytic functions in U รU.
The following subclasses of H(U รU
)are defined in [27]:
Hฮถ [a, n] =
f โ H(U รU
): f (z, ฮถ) = a + an(ฮถ)zn + an+1(ฮถ)zn+1 + . . . , z โ U, ฮถ โ U
with ak(ฮถ) holomorphic functions in U, k โฅ n, a โ C, n โ N.
HฮถU(U) =
f โ Hฮถ [a, n] : f (ยท, ฮถ) univalent in U for all ฮถ โ U
Aฮถn =
f โ H(U รU
): f (z, ฮถ) = z + an+1(ฮถ)zn+1 + . . . , z โ U, ฮถ โ U
, with Aฮถ1 = Aฮถ
and ak(ฮถ) holomorphic functions in U, k โฅ n + 1, n โ N.
Sโฮถ =
f โ Aฮถ : Re
z f โฒz(z, ฮถ)
f (z, ฮถ)> 0, z โ U, ฮถ โ U
denotes the class of starlike functions in U รU.
Kฮถ =
f โ Aฮถ : Re
(z f โฒโฒz2(z, ฮถ)
f โฒz(z, ฮถ)+ 1
)> 0, z โ U, ฮถ โ U
denotes the class of convex functions in U รU.For obtaining the original results of this paper, the following definitions and notations
introduced in [27] are necessary:
Definition 1 ([27]). Let h(z, ฮถ)and f (z, ฮถ) be analytic functions in UรU. The function f (z, ฮถ) issaid to be strongly subordinate to h(z, ฮถ), or h(z, ฮถ) is said to be strongly superordinate to f (z, ฮถ) ifthere exists a function w analytic in U with w(0) = 0, |w(z)| < 1 such that f (z, ฮถ) = h(w(z), ฮถ),for all ฮถ โ U, z โ U. In such a case, we write
f (z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
h(z, ฮถ), z โ U, ฮถ โ U.
Remark 1 ([27]). (a) If f (z, ฮถ) is analytic in U ร U and univalent in U for ฮถ โ U, thenDefinition 1 is equivalent to:
f (0, ฮถ) = h(0, ฮถ), for all ฮถ โ U and f(U รU
)โ h
(U รU
).
(b) If f (z, ฮถ) = f (z), h(z, ฮถ) = h(z), then the strong superordination becomes the usual superordination.
Definition 2 ([27]). We denote by Qฮถ the set of functions q(ยท, ฮถ) that are analytic and injective, asfunction of z, on U\E(q(z, ฮถ)) where
E(q(z, ฮถ)) =
ฮพ โ โU : lim
zโฮพq(z, ฮถ) = โ
and are such that qโฒz(ฮพ, ฮถ) 6= 0 for ฮพ โ โU\E(q(z, ฮถ)), ฮถ โ U.
Axioms 2022, 11, 209 3 of 13
The subclass of Qฮถ for which q(0, ฮถ) = a is denoted by Qฮถ(a).
Definition 3 ([27]). Let ฮฉฮถ be a set in C, q(ยท, ฮถ) โ ฮฉฮถ , and n a positive integer. The class ofadmissible functions ฮฆn
[ฮฉฮถ , q(ยท, ฮถ)
]consists of those functions ฯ : C3 รU รU โ C that satisfy
the admissibility conditionฯ(r, s, t; ฮพ, ฮถ) โ ฮฉฮถ (A)
whenever r = q(z, ฮถ), s = zqโฒz(z, ฮถ)m , Re
( ts + 1
)โค 1
m Re[
zqโฒโฒz2 (z,ฮถ)
qโฒz(z,ฮถ) + 1]
, z โ U, ฮพ โ U\E(q(ยท, ฮถ))
and m โฅ n โฅ 1. When n = 1 we write ฮฆ1[ฮฉฮถ , q(ยท, ฮถ)
]as ฮฆ
[ฮฉฮถ , q(ยท, ฮถ)
].
In the special case when h(ยท, ฮถ) is an analytic mapping of U รU onto ฮฉฮถ 6= C we denote the classฮฆn[h(U รU
), q(z, ฮถ)
]by ฮฆn[h(z, ฮถ) , q(z, ฮถ)].
If ฯ : C2 รU รU โ C , then the admissibility condition (A) reduces to
ฯ
(q(z, ฮถ),
zqโฒz(z, ฮถ)
m; ฮพ, ฮถ
)โ ฮฉฮถ , (Aโ)
where z โ U, ฮถ โ U, ฮพ โ U\E(q(ยท, ฮถ)) and m โฅ n โฅ 1.
MillerโMocanu lemma given in [18] was rewritten in [27] for functions p(z, ฮถ) andq(z, ฮถ) as follows:
Lemma 1 ([17,27]). Let p(z, ฮถ) โ Q(a) and let q(z, ฮถ) = a + an(ฮถ)zn + an+1(ฮถ)zn+1 + . . . withak(ฮถ) holomorphic functions in U, k โฅ n, q(z, ฮถ) 6โก a and n โฅ 1. If q(z, ฮถ) is not subordinateto p(z, ฮถ), then there exist points z0 = r0eiฮธ0 โ U and ฮพ0 โ โU\E(p(z, ฮถ)) and an m โฅ n โฅ 1for which q
(U รUr0
)โ p
(U รU
)and
(i) q(z0, ฮถ) = p(ฮพ0, ฮถ),(ii) z0qโฒz(z0, ฮถ) = mฮพ0 pโฒz(ฮพ0, ฮถ) and
(iii) Re(
z0qโฒโฒz2 (z0, ฮถ)
qโฒz(z0, ฮถ)+ 1)โฅ mRe
(ฮพ0 pโฒโฒ
z2 (ฮพ0, ฮถ)
pโฒz(ฮพ0, ฮถ)+ 1)
.
This lemma will be used in the next section for proving the theorems which containthe original results. Another helpful result which will be used is the next lemma provedin [28].
Lemma 2 ([28]). Let h(z, ฮถ) be convex in U for all ฮถ โ U with h(0, ฮถ) = a, ฮณ 6= 0, Re ฮณ > 0and p โ Hฮถ [a, 1] โฉQ. If p(z, ฮถ) +
zpโฒz(z, ฮถ)ฮณ is univalent in U for all ฮถ โ U,
h(z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
p(z, ฮถ) +zpโฒz(z, ฮถ)
ฮณ
and
q(z, ฮถ) =ฮณ
zฮณ
zโซ0
h(t, ฮถ)tฮณโ1dt,
then
q(z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
p(z, ฮถ), z โ U, ฮถ โ U.
The function q is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions wasestablished in 1985 when de Branges used the generalized hypergeometric function forproving Bieberbachโs conjecture [29]. Once hypergeometric functions were consideredin studies regarding univalent functions, confluent hypergeometric function was used inmany investigations. One of the first papers which investigated confluent hypergeometric
Axioms 2022, 11, 209 4 of 13
function and gave conditions for its univalence was published in 1990 [30]. Ever sincethen, aspects of its univalence were further investigated [31,32], it was considered inconnection with other important functions [33โ37] and it was used in the definition ofnew operators [38]. This prolific function is used in the present paper for obtaining resultsrelated to another topic, strong differential superordinations. The function is consideredas follows:
Definition 4 ([30]). Let a and c be complex numbers with c 6= 0,โ1,โ2, . . . and consider
ฯ(a, c; z) = 1 +acยท z1!
+a(a + 1)c(c + 1)
ยท z2
2!+ . . . , z โ U (1)
This function is called confluent (Kummer) hypergeometric function, is analytic in C, and satisfiesKummerโs differential equation:
zยทwโฒโฒ(z) + [cโ z]ยทwโฒ(z)โ aยทw(z) = 0.
If we let
(d)k =ฮ(d + k)
ฮ(d)= d(d + 1)(d + 2) . . . (d + kโ 1) and (d)0 = 1,
then (1) can be written in the form
ฯ(a, c; z) =โ
โk=0
(a)k(c)kยท z
k
k!=
ฮ(c)ฮ(a)
ยทโ
โk=0
ฮ(a + k)ฮ(c + k)
ยท zk
k!(2)
In the study conducted for obtaining the original results presented in the next sectionof this paper, the operators introduced in [38] are adapted to the subclasses of H
(U รU
)defined in [27] as follows:
Definition 5 ([38]). Let ฯ(a, c; z) be given by (1) and let ฮณ > 0. The integral operatorB : Hฮถ [1, 1]โ Hฮถ [1, 1],
B[ฯ(a(ฮถ), c(ฮถ); z, ฮถ)] = B(a(ฮถ), c(ฮถ); z, ฮถ) =ฮณ
zฮณ
zโซ0
ฯ(a(ฮถ), c(ฮถ); t, ฮถ)tฮณโ1dt (3)
z โ U, ฮถ โ U, is called KummerโBernardi integral operator.For ฮณ = 1 the integral operator L : Hฮถ [1, 1]โ Hฮถ [1, 1] is defined as
L[ฯ(a(ฮถ), c(ฮถ); z, ฮถ)] = L(a(ฮถ), c(ฮถ); z, ฮถ) =1z
zโซ0
ฯ(a(ฮถ), c(ฮถ); t, ฮถ)dt, (4)
z โ U, ฮถ โ U , which is called KummerโLibera integral operator.
The form of the confluent hypergeometric function adapted to the new classes de-pending on the extra parameter ฮถ needed in the studies related to strong differentialsuperordination theory is given in the next section. Strong differential superordinations areproved in the theorems for which the operators given by (3) and (4) and their derivativeswith respect to z are the best subordinants considering ฮณ in relation (3) both a real number,ฮณ > 0, and a complex number with Re ฮณ > 0. Examples are constructed as proof of theapplicability of the new results.
Axioms 2022, 11, 209 5 of 13
2. Main Results
Considering confluent hypergeometric function defined by (1) or (2), if coefficients aand c complex numbers are replaced by holomorphic functions a(ฮถ), c(ฮถ) depending onthe parameter ฮถ โ U, the function changes its form into the following:
ฯ(a(ฮถ), c(ฮถ); z, ฮถ) = 1 +a(ฮถ)c(ฮถ)ยท z1!
+a(ฮถ)[a(ฮถ) + 1]c(ฮถ)[c(ฮถ) + 1]
ยท z2
2!+ . . . , z โ U, (5)
where (ฮถ) 6= 0, c(ฮถ) 6= 0,โ1,โ2, . . ..In [32], Corollary 4 the convexity in the unit disc of the function ฯ(a, c; z) given by (1)
was proved. This property extends to the new form of the function (a(ฮถ), c(ฮถ); z, ฮถ), as seenin (5).
The first original theorem presented in this paper uses the convexity of the functionฯ(a(ฮถ), c(ฮถ); z, ฮถ) and the methods related to strong differential superordination theoryin order to find necessary conditions for KummerโBernardi integral operator presentedin Definition 5 to be the best subordinant of a certain strong differential superordinationinvolving confluent hypergeometric function ฯ(a(ฮถ), c(ฮถ); z, ฮถ).
Theorem 1. Consider the confluent hypergeometric function ฯ(a(ฮถ), c(ฮถ); z, ฮถ) defined by (5) andKummerโBernardi integral operator B(a(ฮถ), c(ฮถ); z, ฮถ) given by (3). Let ฯ : C2 รU รU โ C bean admissible function with the properties seen in Definition 3. Suppose that ฯ(a(ฮถ), c(ฮถ); z, ฮถ) is aunivalent solution of the equation
ฯ(a(ฮถ), c(ฮถ); z, ฮถ) = ฯ(
B(a(ฮถ), c(ฮถ); z, ฮถ), zยทBโฒz(a(ฮถ), c(ฮถ); z, ฮถ); z, ฮถ). (6)
If ฯ โ ฮฆn[h(U รU
), q(z, ฮถ)
], p(z, ฮถ) โ Qฮถ(1) and ฯ(p(z, ฮถ), zยทpโฒz(z, ฮถ); z, ฮถ) are univalent in
U for all ฮถ โ U, then strong superordination
ฯ(a(ฮถ), c(ฮถ); z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
ฯ(
p(z, ฮถ), zยทpโฒz(z, ฮถ); z, ฮถ)
(7)
implies
B(a(ฮถ), c(ฮถ); z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
p(z, ฮถ), z โ U, ฮถ โ U.
The function q(z, ฮถ) = B(a(ฮถ), c(ฮถ); z, ฮถ) is the best subordinant.
Proof. Using relation (3) we obtain
zฮณยทB(a(ฮถ), c(ฮถ); z, ฮถ) = ฮณ
zโซ0
ฯ(a(ฮถ), c(ฮถ); t, ฮถ)tฮณโ1dt. (8)
Differentiating (8) with respect to z, following a simple calculation, the next equationis obtained:
B(a(ฮถ), c(ฮถ); z, ฮถ) +1ฮณ
zยทBโฒz(a(ฮถ), c(ฮถ); z, ฮถ); z, ฮถ) = ฯ(a(ฮถ), c(ฮถ); z, ฮถ). (9)
Using relation (9), strong superordination (7) becomes:
B(a(ฮถ), c(ฮถ); z, ฮถ) +1ฮณ
zยทBโฒz(a(ฮถ), c(ฮถ); z, ฮถ); z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
ฯ(
p(z, ฮถ), zยทpโฒz(z, ฮถ); z, ฮถ). (10)
Let ฯ : C2 รU รU โ C be an admissible function, ฯ(r, s; z, ฮถ) โ ฮฆn[h(UรU
), q(z, ฮถ)
],
defined by:
ฯ(r, s; z, ฮถ) = r +1ฮณ
s, r, s โ C, ฮณ > 0. (11)
Taking r = B(a(ฮถ), c(ฮถ); z, ฮถ), s = zยทBโฒz(a(ฮถ), c(ฮถ); z, ฮถ); z, ฮถ) relation (11) becomes:
Axioms 2022, 11, 209 6 of 13
ฯ(B(a(ฮถ), c(ฮถ); z, ฮถ), zยทBโฒz(a(ฮถ), c(ฮถ); z, ฮถ); z, ฮถ) )= B(a(ฮถ), c(ฮถ); z, ฮถ) + 1
ฮณ zยทBโฒz(a(ฮถ), c(ฮถ); z, ฮถ); z, ฮถ). (12)
Using relation (12) in (10) we get:
ฯ(
B(a(ฮถ), c(ฮถ); z, ฮถ), zยทBโฒz(a(ฮถ), c(ฮถ); z, ฮถ); z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
ฯ(
p(z, ฮถ), zยทpโฒz(z, ฮถ); z, ฮถ).
Using Definition 1 and Remark 1, a), considering strong differential subordination (7)we get:
ฯ(a(ฮถ), c(ฮถ); 0, ฮถ) = ฯ(p(0, ฮถ), 0; 0, ฮถ)
andฯ(U รU
)โ ฯ
(U รU
). (13)
Interpreting relation (13) we conclude that
ฯ(
p(ฮพ, ฮถ), ฮพยทpโฒz(ฮพ, ฮถ); ฮพ, ฮถ)
/โ ฯ(U รU
), ฮพ โ โU, ฮถ โ U. (14)
For ฮพ = ฮพ0 โ โU, relation (14) becomes:
ฯ(
p(ฮพ0, ฮถ), ฮพ0ยทpโฒz(ฮพ0, ฮถ); ฮพ0, ฮถ)
/โ ฯ(U รU
), ฮถ โ U. (15)
Using relation (6) we get:
ฯ(
B(a(ฮถ), c(ฮถ); z, ฮถ), zยทBโฒz(a(ฮถ), c(ฮถ); z, ฮถ); z, ฮถ)โ ฯ
(U รU
), z โ U, ฮถ โ U. (16)
For z = z0 โ U, (16) is written as:
ฯ(
B(a(ฮถ), c(ฮถ); z0, ฮถ), z0ยทBโฒz(a(ฮถ), c(ฮถ); z0, ฮถ); z0, ฮถ)โ ฯ
(U รU
), z0 โ U, ฮถ โ U. (17)
In order to finalize the proof, Lemma 1 and admissibility condition (Aโฒ) will be applied.Suppose that q(z, ฮถ) = B(a(ฮถ), c(ฮถ); z, ฮถ) is not subordinate to p(z, ฮถ) for z โ U, ฮถ โ U.
Then, using Lemma 1, we know that there are points z0 = r0eiฮธ0 โ U and ฮพ0 โ โU\E(p(z, ฮถ))and an m โฅ n โฅ 1such that
(z0, ฮถ) = B(a(ฮถ), c(ฮถ); z0, ฮถ) = p(ฮพ0, ฮถ) and
z0ยทqโฒz(z0, ฮถ) = z0ยทBโฒz(a(ฮถ), c(ฮถ); z0, ฮถ) = mฮพ0 pโฒz(ฮพ0, ฮถ).
Using those conditions with r = q(z0, ฮถ) and s = z0ยทqโฒz(z0,ฮถ)m for ฮพ = ฮพ0 in Definition 3
and taking into consideration the admissibility condition (Aโฒ), we obtain:
ฯ(p(ฮพ0, ฮถ), ฮพ0pโฒz(ฮพ0, ฮถ); ฮพ0, ฮถ) = ฯ(
B(a(ฮถ), c(ฮถ); z0, ฮถ), z0ยทBโฒz(a(ฮถ),c(ฮถ);z0,ฮถ)m ; z0, ฮถ
)โ ฯ
(U รU
).
Using m = 1 in the previous relation, we get
ฯ(p(ฮพ0, ฮถ), ฮพ0 pโฒz(ฮพ0, ฮถ); ฮพ0, ฮถ) = ฯ(B(a(ฮถ), c(ฮถ); z0, ฮถ), z0ยทBโฒz(a(ฮถ), c(ฮถ); z0, ฮถ); z0, ฮถ)โ ฯ
(U รU
)and using (17) we write
ฯ(
p(ฮพ0, ฮถ), ฮพ0pโฒz(ฮพ0, ฮถ); ฮพ0, ฮถ)โ ฯ
(U รU
), z โ U, ฮถ โ U,
which contradicts the result obtained in relation (15). Hence, the assumption made is falseand we must have:
B(a(ฮถ), c(ฮถ); z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
p(z, ฮถ) for z โ U, ฮถ โ U.
Axioms 2022, 11, 209 7 of 13
Since q(z, ฮถ) = B(a(ฮถ), c(ฮถ); z, ฮถ) satisfies the differential Equation (6), we concludethat q(z, ฮถ) = B(a(ฮถ), c(ฮถ); z, ฮถ) is the best subordinant.
Remark 2. For ฮณ = 1, instead of KummerโBernardi integral operator, KummerโLibera integraloperator defined in (4) is used in Theorem 1 and the following corollary can be written:
Corollary 1. Consider the confluent hypergeometric function ฯ(a(ฮถ), c(ฮถ); z, ฮถ) defined by (5) andKummerโLibera integral operator L(a(ฮถ), c(ฮถ); z, ฮถ) given by (4). Let ฯ : C2 รU รU โ C bean admissible function with the properties seen in Definition 3. Suppose that ฯ(a(ฮถ), c(ฮถ); z, ฮถ) is aunivalent solution of the equation
ฯ(a(ฮถ), c(ฮถ); z, ฮถ) = ฯ(
L(a(ฮถ), c(ฮถ); z, ฮถ), zยทLโฒz(a(ฮถ), c(ฮถ); z, ฮถ); z, ฮถ).
If ฯ โ ฮฆn[h(U รU
), q(z, ฮถ)
], p(z, ฮถ) โ Qฮถ(1) and ฯ(p(z, ฮถ), zยทpโฒz(z, ฮถ); z, ฮถ) are univalent in
U for allฮถ โ U, then strong superordination
ฯ(a(ฮถ), c(ฮถ); z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
ฯ(
p(z, ฮถ), zยทpโฒz(z, ฮถ); z, ฮถ)
implies
L(a(ฮถ), c(ฮถ); z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
p(z, ฮถ), z โ U, ฮถ โ U.
The function q(z, ฮถ) = L(a(ฮถ), c(ฮถ); z, ฮถ) is the best subordinant.
Theorem 2. Let q(z, ฮถ) be a convex function in the unit disc for all ฮถ โ U, consider the confluenthypergeometric function ฯ(a(ฮถ), c(ฮถ); z, ฮถ) defined by (5) and KummerโBernardi integral operatorB(a(ฮถ), c(ฮถ); z, ฮถ) given by (3). Let ฯ : C2 รU รU โ C be an admissible function with theproperties seen in Definition 3 and define the analytic function
h(z, ฮถ) =
(1 +
1ฮณ
)q(z, ฮถ) +
1ฮณ
zยทqโฒz(z, ฮถ), z โ U, ฮถ โ U.
If ฯโฒz(a(ฮถ), c(ฮถ); z, ฮถ) and Bโฒz(a(ฮถ), c(ฮถ); z, ฮถ) โ Hฮถ [1, 1]โฉQฮถ(1) are univalent functions in U forall ฮถ โ U, then strong differential superordination
h(z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
ฯโฒz(a(ฮถ), c(ฮถ); z, ฮถ) (18)
implies
q(z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
Bโฒz(a(ฮถ), c(ฮถ); z, ฮถ), z โ U, ฮถ โ U.
Proof. Using relation (9) from the proof of Theorem 1 and differentiating it with respect toz, we obtain:
ฯโฒz(a(ฮถ), c(ฮถ); z, ฮถ) =
(1 +
1ฮณ
)Bโฒz(a(ฮถ), c(ฮถ); z, ฮถ) +
1ฮณ
zยทBโฒโฒz2(a(ฮถ), c(ฮถ); z, ฮถ), z โ U, ฮถ โ U. (19)
Using (19), strong differential superordination (18) becomes:
h(z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
(1 +
1ฮณ
)Bโฒz(a(ฮถ), c(ฮถ); z, ฮถ) +
1ฮณ
zยทBโฒโฒz2(a(ฮถ), c(ฮถ); z, ฮถ). (20)
For the proof of this theorem to be complete, Lemma 1 and the admissibility condition(Aโฒ) will be applied.
In order to do that, we define the admissible function ฯ : C2 รU รU โ C ,ฯ(r, s; z, ฮถ) โ ฮฆn
[h(U รU
), q(z, ฮถ)
], given by:
ฯ(r, s; z, ฮถ) =
(1 +
1ฮณ
)r +
1ฮณ
s, r, s โ C, ฮณ > 0. (21)
Axioms 2022, 11, 209 8 of 13
Taking r = Bโฒz(a(ฮถ), c(ฮถ); z, ฮถ), s = zยทBโฒโฒz2(a(ฮถ), c(ฮถ); z, ฮถ) relation (21) becomes:
ฯ(
Bโฒz(a(ฮถ), c(ฮถ); z, ฮถ), zยทBโฒโฒz2(a(ฮถ), c(ฮถ); z, ฮถ); z, ฮถ)
=(
1 + 1ฮณ
)Bโฒz(a(ฮถ), c(ฮถ); z, ฮถ) + 1
ฮณ zยทBโฒโฒz2(a(ฮถ), c(ฮถ); z, ฮถ); z, ฮถ).(22)
Using relation (22) in (20) we get:
h(z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
ฯ(
Bโฒz(a(ฮถ), c(ฮถ); z, ฮถ), zยทBโฒโฒz2(a(ฮถ), c(ฮถ); z, ฮถ); z, ฮถ)
.
Using Definition 1 and Remark 1, a) for this strong differential superordination, we get:
h(0, ฮถ) = ฯ(
Bโฒz(a(ฮถ), c(ฮถ); 0, ฮถ), 0; 0, ฮถ)
andh(U รU
)โ ฯ
(U รU
). (23)
Interpreting relation (23) we conclude that
ฯ(
Bโฒz(a(ฮถ), c(ฮถ); ฮพ, ฮถ), ฮพยทBโฒโฒz2(a(ฮถ), c(ฮถ); ฮพ, ฮถ); ฮพ, ฮถ)
/โ h(U รU
), ฮพ โ โU, ฮถ โ U. (24)
For ฮพ = ฮพ0 โ โU, relation (24) becomes:
ฯ(
Bโฒz(a(ฮถ), c(ฮถ); ฮพ0, ฮถ), ฮพ0ยทBโฒโฒz2(a(ฮถ), c(ฮถ); ฮพ0, ฮถ); ฮพ0, ฮถ)
/โ h(U รU
), ฮถ โ U. (25)
Suppose that q(z, ฮถ) is not subordinate to Bโฒz(a(ฮถ), c(ฮถ); z, ฮถ) for z โ U, ฮถ โ U. Then, usingLemma 1, we know that there are points z0 = r0eiฮธ0 โ U and ฮพ0 โ โU\E(Bโฒz(a(ฮถ), c(ฮถ); z, ฮถ))and an m โฅ n โฅ 1 such that
q(z0, ฮถ) = Bโฒz(a(ฮถ), c(ฮถ); z0, ฮถ) = p(ฮพ0, ฮถ) and
z0qโฒz(z0, ฮถ) = mฮพ0Bโฒโฒz2(a(ฮถ), c(ฮถ); z0, ฮถ) = mฮพ0 pโฒz(ฮพ0, ฮถ).
Using those conditions with r = Bโฒz(a(ฮถ), c(ฮถ); z0, ฮถ) and s = ฮพ0Bโฒโฒz2(a(ฮถ), c(ฮถ); z0, ฮถ)for ฮพ = ฮพ0 in Definition 3 and taking into consideration the admissibility condition (Aโฒ),we obtain:
ฯ(q(z0, ฮถ), z0qโฒz(z0, ฮถ); z0, ฮถ) = ฯ
(Bโฒz(a(ฮถ), c(ฮถ); z0, ฮถ),
ฮพ0Bโฒโฒz2 (a(ฮถ),c(ฮถ);ฮพ0,ฮถ)
m ; z0, ฮถ
)โ h(U รU
).
Using m = 1 in the previous relation, we get
ฯ(
Bโฒz(a(ฮถ), c(ฮถ); z0, ฮถ), ฮพ0Bโฒโฒz2(a(ฮถ), c(ฮถ); z0, ฮถ); z0, ฮถ)โ h(U รU
), ฮถ โ U,
which contradicts the result obtained in relation (25). Hence, the assumption made is falseand we must have:
q(z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
Bโฒz(a(ฮถ), c(ฮถ); z, ฮถ) for z โ U, ฮถ โ U.
Remark 3. For ฮณ = 1, instead of KummerโBernardi integral operator, KummerโLibera integraloperator defined in (4) is used in Theorem 2 and the following corollary can be written:
Corollary 2. Let q(z, ฮถ) be a convex function in the unit disc for all ฮถ โ U, consider the confluenthypergeometric function ฯ(a(ฮถ), c(ฮถ); z, ฮถ) defined by (5) and KummerโLibera integral operator
Axioms 2022, 11, 209 9 of 13
L(a(ฮถ), c(ฮถ); z, ฮถ) given by (4). Let ฯ : C2 รU รU โ C be an admissible function with theproperties seen in Definition 3 and define the analytic function:
h(z, ฮถ) =
(1 +
1ฮณ
)q(z, ฮถ) +
1ฮณ
zยทqโฒz(z, ฮถ), z โ U, ฮถ โ U.
If ฯโฒz(a(ฮถ), c(ฮถ); z, ฮถ) and Lโฒz(a(ฮถ), c(ฮถ); z, ฮถ) โ Hฮถ [1, 1]โฉQฮถ(1) are univalent functions in U forall ฮถ โ U, then strong differential superordination
h(z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
ฯโฒz(a(ฮถ), c(ฮถ); z, ฮถ)
implies
q(z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
Lโฒz(a(ฮถ), c(ฮถ); z, ฮถ), z โ U, ฮถ โ U.
In Theorems 1 and 2, parameter ฮณ is a real number, ฮณ > 0. In the next theorem,a necessary and sufficient condition is determined such that KummerโBernardi integraloperator is the best subordinant for a certain strong differential superordination consideringฮณ a complex number with Re ฮณ > 0.
Theorem 3. Let h(z, ฮถ) with h(0, ฮถ) = a be a convex function in the unit disc for all ฮถ โ U andlet ฮณ be a complex number with Re ฮณ > 0. Consider the confluent hypergeometric functionฯ(a(ฮถ), c(ฮถ); z, ฮถ) defined by (5) and KummerโBernardi integral operator B(a(ฮถ), c(ฮถ); z, ฮถ) givenby (3). Let p(z, ฮถ) โ Hฮถ [a, 1] โฉQฮถ(a).
If p(z, ฮถ) +zยทpโฒz(z,ฮถ)
ฮณ is univalent in U for all ฮถ โ U and the following strong differential superordi-nation is satisfied
B(a(ฮถ), c(ฮถ); z, ฮถ) +zยทBโฒz(a(ฮถ), c(ฮถ); z, ฮถ)
ฮณ
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
p(z, ฮถ) +zยทpโฒz(z, ฮถ)
ฮณ, (26)
then
q(z, ฮถ) = B(a(ฮถ), c(ฮถ); z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
p(z, ฮถ), z โ U, ฮถ โ U.
Function q(z, ฮถ) = B(a(ฮถ), c(ฮถ); z, ฮถ) is convex and is the best subordinant.
Proof. Lemma 2 will be used for the proof of this theorem. Using the definition of KummerโBernardi operator given by (3) and differentiating this relation with respect to z, we obtain:
ฮณยทzฮณโ1ยทB(a(ฮถ), c(ฮถ); z, ฮถ) + zฮณยทBโฒz(a(ฮถ), c(ฮถ); z, ฮถ) = ฮณยทh(z, ฮถ)ยทzฮณโ1, z โ U, ฮถ โ U.
After a simple calculation, we get:
B(a(ฮถ), c(ฮถ); z, ฮถ) +zยทBโฒz(a(ฮถ), c(ฮถ); z, ฮถ)
ฮณ= h(z, ฮถ), z โ U, ฮถ โ U. (27)
Using (27), the strong differential subordination (26) becomes
h(z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
p(z, ฮถ) +zยทpโฒz(z, ฮถ)
ฮณ, z โ U, ฮถ โ U.
Since h(z, ฮถ) is a convex function and p(z, ฮถ) +zยทpโฒz(z,ฮถ)
ฮณ is univalent in U for allฮถ โ U, by applying Lemma 2 we obtain:
q(z, ฮถ) = B(a(ฮถ), c(ฮถ); z, ฮถ)
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
p(z, ฮถ), z โ U, ฮถ โ U.
Since function q(z, ฮถ) = B(a(ฮถ), c(ฮถ); z, ฮถ) satisfies Equation (27) and is analytic in Ufor all ฮถ โ U, we conclude that q(z, ฮถ) = B(a(ฮถ), c(ฮถ); z, ฮถ) is the best subordinant.
Example 1. Let a = โ1, c = i2ฮถ , i
2ฮถ 6= 0,โ1,โ2, . . . , ฮถ 6= 0, ฮณ โ C, Re ฮณ > 0. We evaluate:
Axioms 2022, 11, 209 10 of 13
ฯ
(โ1,
i2ฮถ
; z, ฮถ
)= 1 +
โ1i
2ฮถ
ยท z1!
= 1โ 2ฮถยทzi
= 1 + 2iฮถz.
Further, we use this expression to obtain KummerโBernardi integral operatorโs expression:
B(
ฯ(โ1, i
2ฮถ ; z, ฮถ))
= ฮณzฮณ
zโซ0
ฯ(โ1, i
2ฮถ ; t, ฮถ)
tฮณโ1dt = ฮณzฮณ
zโซ0(1 + 2iฮถt)tฮณโ1dt
= ฮณzฮณ
(zฮณ
ฮณ + 2iฮถ zฮณ+1
ฮณ+1
)= 1 + 2iฮถ ฮณ
ฮณ+1 ยทz.
Functions p(z, ฮถ) = 1 + zฮถ and p(z, ฮถ) +zยทpโฒz(z,ฮถ)
ฮณ = 1 + z(
ฮถ + ฮถฮณ
)are univalent in U for
all ฮถ โ U.Using Theorem 3, we get:If the following strong differential superordination is satisfied
1 + 2iฮถฮณ
ฮณ + 1ยทz + 2iฮถยทz
ฮณ + 1
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
1 + z(
ฮถ +ฮถ
ฮณ
),
then
1 + 2iฮถฮณ
ฮณ + 1ยทz
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
1 + zฮถ, z โ U, ฮถ โ U.
Function q(z, ฮถ) = 1 + 2iฮถ ฮณฮณ+1 ยทz is convex and is the best subordinant.
Example 2. Let a = โ1, c = i2ฮถ , i
2ฮถ 6= 0,โ1,โ2, . . . , ฮถ 6= 0, ฮณ = 1 + i โ C, Re ฮณ = 1 > 0.We evaluate:
ฯ
(โ1,
i2ฮถ
; z, ฮถ
)= 1 +
โ1i
2ฮถ
ยท z1!
= 1โ 2ฮถยทzi
= 1 + 2iฮถz.
Further, we use this expression to obtain KummerโBernardi integral operatorโs expression:
B(
ฯ(โ1, i
2ฮถ ; z, ฮถ))
= ฮณzฮณ
zโซ0
ฯ(โ1, i
2ฮถ ; t, ฮถ)
tฮณโ1dt = 1+iz1+i
zโซ0(1 + 2iฮถt)tฮณโ1dt
= 1+iz1+i
(z1+i
1+i + 2iฮถ z1+i+1
1+i+1
)= 1 + 2iฮถ z(i+1)
i+2 = 1 + 25 (โ1 + 3i)zฮถ.
Functions p(z, ฮถ) = 1 + zฮถ and p(z, ฮถ) +zยทpโฒz(z,ฮถ)
1+i = 1 + 32 zฮถ(3โ i) are univalent in U for all
ฮถ โ U.Using Theorem 3, we get:If 1 + 3
2 zฮถ(3โ i) is univalent in U for all ฮถ โ U and the following strong differential superordina-tion is satisfied
1 + 2iฮถt
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
1 +32
zฮถ(3โ i),
then
1 +25(โ1 + 3i)zฮถ
Axioms 2022, 11, x FOR PEER REVIEW 3 of 12
Definition 3. [27] Let ๐บ be a set in โ, ๐(โ, ๐) โ ๐บ , and ๐ a positive integer. The class of ad-missible functions ๐ท ๐บ , ๐(โ, ๐) consists of those functions ๐: โ ร ๐ ร ๐ โ โ that satisfy the admissibility condition ๐(๐, ๐ , ๐ก; ๐, ๐) โ ๐บ (A)
whenever ๐ = ๐(๐ง, ๐), ๐ = ( , ) , ๐ ๐ + 1 โค ๐ ๐ '' ( , )' ( , ) + 1 , ๐ง โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. When ๐ = 1 we write ฮฆ ๐บ , ๐(โ, ๐) as ฮฆ ๐บ , ๐(โ, ๐) . In the special case when โ(โ, ๐) is an analytic mapping of ๐ ร ๐ onto ๐บ โ โ we denote the class ฮฆ โ(๐ ร ๐) , ๐(๐ง, ๐) by ฮฆ โ(๐ง, ๐) , ๐(๐ง, ๐) . If ๐: โ ร ๐ ร ๐ โ โ, then the admissibility condition (A) reduces to ๐ ๐(๐ง, ๐), ๐ง๐ (๐ง, ๐)๐ ; ๐, ๐ โ ๐บ , (Aโ)
where ๐ง โ ๐, ๐ โ ๐, ๐ โ ๐\๐ธ ๐(โ, ๐) and ๐ โฅ ๐ โฅ 1. MillerโMocanu lemma given in [18] was rewritten in [27] for functions ๐(๐ง, ๐) and ๐(๐ง, ๐) as follows:
Lemma 1. ([17],[27]) Let ๐(๐ง, ๐) โ ๐(๐) and let ๐(๐ง, ๐) = ๐ + ๐ (๐)๐ง + ๐ (๐)๐ง + โฏ with ๐ (๐) holomorphic functions in ๐, ๐ โฅ ๐, ๐(๐ง, ๐) โข ๐ and ๐ โฅ 1. If ๐(๐ง, ๐) is not subor-dinate to ๐(๐ง, ๐), then there exist points ๐ง = ๐ ๐ โ ๐ and ๐ โ ๐๐\๐ธ ๐(๐ง, ๐) and an ๐ โฅ๐ โฅ 1 for which ๐(๐ ร ๐ ) โ ๐(๐ ร ๐) and (๐) ๐(๐ง , ๐) = ๐(๐ , ๐), (๐๐) ๐ง ๐ (๐ง , ๐) = ๐๐ ๐ (๐ , ๐) and (๐๐๐) ๐ ๐ ๐ง ๐ (๐ง , ๐)๐ (๐ง , ๐) + 1 โฅ ๐๐ ๐ ๐ ๐ (๐ , ๐)๐ (๐ , ๐) + 1 .
This lemma will be used in the next section for proving the theorems which contain the original results. Another helpful result which will be used is the next lemma proved in [28].
Lemma 2. [28] Let โ(๐ง, ๐) be convex in ๐ for all ๐ โ ๐ with โ(0, ๐) = ๐, ๐พ โ 0, ๐ ๐ ๐พ > 0 and ๐ โ ๐ป ๐, 1 โฉ ๐. If ๐(๐ง, ๐) + ( , ) is univalent in ๐ for all ๐ โ ๐, โ(๐ง, ๐) โชป ๐(๐ง, ๐) + ๐ง๐ (๐ง, ๐)๐พ
and ๐(๐ง, ๐) = ๐พ๐ง โ(๐ก, ๐)๐ก ๐๐ก, then ๐(๐ง, ๐) โชป ๐(๐ง, ๐), ๐ง โ ๐, ๐ โ ๐. The function ๐ is convex and is the best subordinant.
The connection between univalent function theory and hypergeometric functions was established in 1985 when de Branges used the generalized hypergeometric function for proving Bieberbachโs conjecture [29]. Once hypergeometric functions were considered in studies regarding univalent functions, confluent hypergeometric function was used in many investigations. One of the first papers which investigated confluent hypergeometric function and gave conditions for its univalence was published in 1990 [30]. Ever since then, aspects of its univalence were further investigated [31,32], it was considered in con-nection with other important functions [33โ37] and it was used in the definition of new
1 + zฮถ, z โ U, ฮถ โ U.
Function q(z, ฮถ) = 1 + 25 (โ1 + 3i)zฮถ is convex and is the best subordinant.
3. Discussion
The study presented in this paper is inspired by the nice results published whichinvolve confluent hypergeometric function and certain operators defined by using thisinteresting function. For this research, the environment of the theory of strong differential
Axioms 2022, 11, 209 11 of 13
superordination is considered. Confluent hypergeometric function and KummerโBernardiand KummerโLibera operators defined in [38] are used in order to obtain certain strongdifferential superordinations. Their best subordinants are given in the three theoremsproved in the main results part. Theorems 1 and 2 use the convexity of confluent hy-pergeometric function ฯ(a(ฮถ), c(ฮถ); z, ฮถ) given in (5) where it is adapted to certain classesof analytic functions specific for the theory of strong differential superordination. Themethods related to strong differential superordination theory are applied in order to findnecessary conditions for KummerโBernardi integral operator presented in Definition 5,relation (3), to be the best subordinant of a certain strong differential superordinationinvolving confluent hypergeometric function ฯ(a(ฮถ), c(ฮถ); z, ฮถ). As corollary, the similarresult is given for KummerโLibera operator. For those two theorems, the parameter ฮณ isa real number, ฮณ > 0. In Theorem 3, ฮณ โ C, with Re ฮณ > 0 is considered and a necessaryand sufficient condition is determined such that KummerโBernardi integral operator to bethe best subordinant for a certain strong differential superordination. Two examples areconstructed for the case when ฮณ โ C, with Re ฮณ > 0.
4. Conclusions
In this paper, new strong differential superordinations are investigated using a specialform of confluent hypergeometric function given in (5) and two operators previouslyintroduced in [38]. In the three theorems proved as a result of the study, the two operatorscalled KummerโBernardi and KummerโLibera integral operators are the best subordinantsof the strong differential superordinations.
The novelty of the study resides in the forms of the confluent hypergeometric functionand of the two operators considered by adaptation to the new classes depending on theextra parameter ฮถ introduced in the theory of strong differential subordination in [27].
As future studies, the dual notion of strong differential subordination can be con-sidered for investigations concerning confluent hypergeometric function and the twooperators used in the present study. Sandwich-type results could be obtained as seen inrecent papers [13,39,40].
New subclasses of univalent functions could be introduced in the context of strongdifferential subordination and superordination theories using the operators presented inthis paper as seen in [41].
It might also be interesting to consider other hypergeometric functions and operatorsdefined with them following the ideas presented in this paper.
Author Contributions: Conceptualization, G.I.O. and G.O.; methodology, G.I.O., G.O. and A.M.R.;software, G.I.O.; validation, G.I.O., G.O. and A.M.R.; formal analysis, G.I.O. and G.O.; investigation,G.I.O., G.O. and A.M.R.; resources, G.I.O. and G.O.; data curation, G.I.O. and G.O.; writingโoriginaldraft preparation, G.O.; writingโreview and editing, G.I.O. and A.M.R.; visualization, G.I.O. andA.M.R.; supervision, G.O.; project administration, G.I.O.; funding acquisition, G.I.O. and A.M.R. Allauthors 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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