Abstract
Over the past ten years, analytical functions’ reputation in the literature and their application have grown. We study some practical issues pertaining to multivalent functions with bounded boundary rotation that associate with the combination of confluent hypergeometric functions and binomial series in this research. A novel subset of multivalent functions is established through the use of convolution products and specific inclusion properties are examined through the application of second order differential inequalities in the complex plane. Furthermore, for multivalent functions, we examined inclusion findings using Bernardi integral operators. Moreover, we will demonstrate how the class proposed in this study, in conjunction with the acquired results, generalizes other well-known (or recently discovered) works that are called out as exceptions in the literature.
Keywords:
convolution; p-valent functions; binomial series; confluent hypergeometric function; starlike functions; convex functions; close-to-convex functions MSC:
30C50; 30C45; 33C20; 33C05; 33C15
1. Introduction, Definitions and Preliminaries
Assume that is the class of univalent holomorphic (regular/analytic) functions in the unit disc
which have the following form:
Furthermore, the family of univalent functions, as in (2), is indicated by the notation . In 1907, Köebe studied this family . It was Bieberbach [1] who made feasible the most well-known finding in function theory, the “Bieberbach conjecture,” in 1916. Specifically, if , then for all . This result was also established for by him. It is clear that many reputable researchers have used a variety of methods to tackle this problem. Schaeffer and Spencer [2] and Löwner [3] used the variational method and Löwner differential equation, respectively, to settle this hypothesis for . Afterwards, Jenkins [4] used quadratic differentials to prove the same coefficient inequality: . Using the variational technique, Garabedian and Schiffer [5] found that In an effort to address this issue, numerous intriguing subfamilies of the class were developed between 1916 and 1985. Here are some definitions for few basic families:
If a function falls within the range of a given simply connected domain and maps conformally onto an image domain of boundary rotation at most , it is considered to have limited boundary rotation. This is because the function is both locally univalent and analytic. Although Loewner [6] did not use the current terminology, he proposed the idea of functions of bounded boundary rotation for the first time in 1917. Paatero [7] was the one who methodically established their properties and conducted a thorough analysis of the class, demonstrating that if and only if
where is a real-valued function of bounded variation for which
Let be the class of functions analytic in satisfying the features and
where and If , we denote Hence, the class (defined by Pinchuk [8]) denotes the class of analytic functions , with and will be having a representation
where satisfies (3) (for details see [9,10]). From (5), one can easily find that can also be written as
The subject encompasses classes of functions that have greatly advanced geometric function theory, such as bounded radius and bounded boundary rotation. The main tools, such as convolution and subordination, have been extensively used to investigate the geometric characteristics of analytic classes, but many unanswered questions remain. Padmanabhan and Parvatham [11] introduced the class as previously mentioned, and they also conducted a detailed analysis of order referring to Roberston [12]. Additionally, these transformations maintain a number of the geometric properties of the family, such as the subordination, compactness, convexity, and positivity of the real part. They are iterative and are closely associated with certain families of analytic and univalent functions involving the well-known Salagean and Rucheweyh derivatives (see [13,14]) and have been used effectively, and elegantly too, to characterize them. For higher-order derivatives related to the Gaussian hypergeometric function, they can additionally investigate a suitably generalized derivative operator based on subordinations. For example, using both vortex and source/sink methods, an explicit construction for the complicated potential and stream function of two-dimensional fluid flow issues is given throughout a circular cylinder to illustrate the possible practical consequences of this work. One can define a single source’s fluid flow and produce a univalent function in order to turn the source’s image into a source for a particular complicated potential (See [15]). Aleman and Constantin [16] recently revealed an astounding relationship between fluid dynamics and univalent function theory. They specifically presented a straightforward technique that uses a univalent harmonic map to directly solve incompressible two-dimensional Euler equations. It finds extensive application in modern mathematical physics, fluid dynamics, nonlinear integrable system theory, and partial differential equation theory, among other applied scientific disciplines.
1.1. Confluent Hypergeometric Function (CHF)
De Branges’ use of the generalized hypergeometric function to prove Bieberbach’s conjecture in 1985 established the link between univalent function theory and hypergeometric functions [17]. CHFs were employed in numerous investigations, after hypergeometric functions were taken into consideration in studies pertaining to univalent functions. Lately, the CHF of the first kind was given by El-Deeb and Catas [18] as below:
for all finite values of (see [19]) is convergent. It may also be noted as
which is convergent for
The confluent hypergeometric distribution (CHD) whose probability mass function
is given by Porwal and Kumar [20] (see also [21,22,23]). Assume is the class of -valently holomorphic functions in have the following
The convolution of two functions expresses how the geometric representation of one function is improved by the other. The concept clarification covers both the effect function and the calculating method. When one of the functions is moved and inverted, it can be written as the integral, or sum, of the product of the two functions. Let be assumed as
then the Hadamard (or convolution) product of and is assumed as
El-Deeb and Catas [18] introduced a series whose coefficients are probabilities of CHD
and defined a linear operator by the convolution product as follows
Making use of the binomial series
El-Deeb and Catas [18] introduced the linear differential operator by fixing and as below:
where
and
From (9), we obtain that
1.2. Multivalent Functions of Bounded Radius Rotations
Let be the class of functions analytic in satisfying the properties and
where and This class was introduced by Aouf [24] with .
Using (13), we obtain if and only if there exists such that
Remark 1.
We note that:
- (i)
- (see Padmanabhan and Parvatham [11]);
- (ii)
- (see Pinchuk [8] and Robertson [12]);
- (iii)
- where is the class of functions with a positive real part greater than (see [24]);
- (iv)
- where is the class of functions with a positive real part (see [24]); and
- (v)
- where and
Now, for and , we define the following classes and of as below:
and
Obviously, we know that
- where was introduced by Patil and Thakare [25];
- where was introduced by Owa [26];
- where was introduced by Aouf [27].
Paatero [28] noted that when coincides with . Pinchuk [8] also demonstrated that functions in are close-to-convex in if , and are therefore univalent.
This paper’s novel findings are motivated by the excellent outcomes lately achieved through the integral and derivative operators in the field of geometric function theory. Our inspiration to further investigate the binomial series-confluent hypergeometric distribution was sparked by reading about the applications of an operator on new subclasses of univalent functions and how they relate to classical theories of differential subordination and superordination [15,16,29,30,31,32,33] and the references cited therein. This led us to consider the idea of introducing and studying new subclasses of univalent functions in with bounded boundary rotation. Using the operator given in (9), we familiarize the new subclasses of the class as below:
and
It is easy to understand that
In the following section, for functions belonging to this newly-defined analytic function classes, and motivated by the earlier studies on bounded boundary rotations and differential subordination [3,11,24,30,31,33,34] and using following Lemmas 1–3, we discuss inclusion properties involving the differential operator and integral operator
2. Inclusion Properties Involving the Operator
To establish our major results, we will need the following lemmas.
Lemma 1
([34,35]). Assume that is the complex valued function, is the complex plane) and let Suppose that satisfies the following conditions:
- (i)
- is continuous in a domain
- (ii)
- and
- (iii)
- for all and such that
Let be regular in Δ such that for all If
then
Lemma 2
([36]). Let be analytic in Δ with and Then, for and (complex),
where is given by
Lemma 3
([37]). Let to be starlike in and to be convex. If is analytic in Δ with is attained, is contained in the convex hull of .
Unless otherwise mentioned, we assume throughout this paper that: and and the power is the principal values.
Theorem 1.
For we have and for then
where ℵ is given by
Proof.
where
We note that if and only if and From , we obtain ℵ as given by (20) and from we have Thereforeapplying Lemma 1, and consequently for This completes the proof of Theorem 1. □
Let and let
where
and are analytic in with
Using (12) and (21), we have
Differentiating (23) logarithmically with respect to , we have
Now, we show that or From (22) and (24), we have
and this implies that
By fixing and we let . Thus
Then
- (i)
- is continuous in
- (ii)
- and
- (iii)
- For all such that
Theorem 2.
Proof.
Let
which completes the proof. □
Theorem 3.
Let Then,
Proof.
By applying Lemma 1, we have for and consequently for This completes the proof of Theorem 3. □
Let Then, there exists such that
Then We set
where is given by (22). By using (12) in (25), we obtain
Also, and by using Theorem 1, with we have
Therefore, we can write
where is analytic in and . By differentiating (26) with respect to , we obtain
then
From (27) and (28), we obtain
so that
Let
and
We want to show that or for Then, From (26) and (29), we have
and this implies that
By fixing and , we let . Thus,
Then,
- (i)
- is continuous in
- (ii)
- and
- (iii)
- For all such that
Theorem 4.
Let then for
with and This radius is the best possible.
3. Inclusion Properties Based on Bernardi Integral Operator
Choi et al. [38] gave the definition of the generalized Bernardi operator as below:
which satisfies the following relationship:
Theorem 5.
Let and Then,
Proof.
Let
where given by (22). Using (36), we have
From (37) and (38), we have
Differentiating (39) logarithmically with respect to and multiplying by , we have
Now, we show that or for From (22) and (40), we have
and this implies that
We form the function by choosing and Thus,
Clearly, conditions (i), (ii) and (iii) of Lemma 1 are satisfied. By applying Lemma 1, we have for and consequently for This completes the proof of Theorem 5. □
Theorem 6.
Let and Then
Proof.
Let
By applying Theorem 5, it follows that
which perceptibly proves Theorem 6. □
4. Inclusion Properties by Convolution
Theorem 7.
Let Ψ be a convex function and Then, where and
Proof.
To show that it sufficient to show that is contained in the convex hull of Now,
where is analytic in and From Lemma 3, we can see that is contained in the convex hull of since is analytic in and
then lies in ; this implies that . □
Theorem 8.
Let Ψ be a convex function and Then, where and
5. Conclusions
In our present investigation, we have made use of a certain combination binomial series and confluent hypergeometric function with a view to introducing a new subclass of multivalent functions in the open unit disk. For functions belonging to this newly defined analytic function class, we have discussed inclusion properties involving the differential operator and integral operator Further, we discussed radius problems and derived certain inclusion results under convolution. Theorems of differential subordination and superordination for multivalent analytic functions arising in two-dimensional potential flow problems can be discussed later. Additionally, based on the combination of binomial series and confluent hypergeometric functions, these operators were utilized to investigate univalent function theory and fluid dynamics by a differential subordination technique [15,16], dynamic inequalities with general kernels [39,40,41] and by describing various classes of bi-univalent functions [42,43,44,45] with bounded boundary.
Author Contributions
Conceptualization, I.A., S.M.E.-D. and G.M.; methodology, I.A., S.M.E.-D. and G.M.; validation, S.M.E.-D., G.M. and I.A.; formal analysis, I.A., S.M.E.-D. and G.M.; investigation, S.M.E.-D., G.M. and I.A.; resources, I.A., S.M.E.-D. and G.M.; writing—original draft preparation, I.A., S.M.E.-D. and G.M.; writing—review and editing, I.A., S.M.E.-D. and G.M.; supervision, I.A., S.M.E.-D. and G.M.; project administration, I.A., S.M.E.-D. and G.M. All authors have read and agreed to the published version of the manuscript.
Funding
This research is funded by the Ministry of Education in Saudi Arabia through the project number IFP-IMSIU-2023093.
Acknowledgments
The authors extend their appreciation to the Deputyship for Research & Innovation, Ministry of Education in Saudi Arabia for funding this research through the project number IFP-IMSIU-2023093. The authors also appreciate the Deanship of Scientific Research at Imam Mohammad Ibn Saud Islamic University (IMSIU) for supporting and supervising this project.
Conflicts of Interest
The authors declare no conflict of interest.
References
- Bieberbach, L. Über dié koeffizienten derjenigen Potenzreihen, welche eine schlichte Abbildung des Einheitskreises vermitteln. Sitzungsberichte Preuss. Akad. Der Wiss. 1916, 138, 940–955. [Google Scholar]
- Schaeffer, A.C.; Spencer, D.C. The coefficients of schlicht functions. Duke Math. J. 1943, 10, 611–635. [Google Scholar] [CrossRef]
- Löwner, K. Untersuchungen iiber schlichte konforme Abbildungen des Einheitskreises. Math. Ann. 1923, 89, 103–121. [Google Scholar] [CrossRef]
- Jenkins, J.A. On certain coefficients of univalent functions II. Trans. Am. Math. Soc. 1960, 96, 534–545. [Google Scholar] [CrossRef]
- Garabedian, P.R.; Schiffer, M. A proof of the Bieberbach conjecture for the fourth coefficient. J. Ration. Mech. Anal. 1955, 4, 428–465. [Google Scholar] [CrossRef]
- Loewner, C. Untersuchungen uber die Verzerrung bie Konformen abbildungen des Einheitskreises |z|<1, die durch Funktionen mit nicht verschwinden der Ableitung geliefert werden. Ber. Verh. Sachs. Ges. Wiss. Leipzig 1917, 69, 89–106. [Google Scholar]
- Paatero, V. Uber die konforme Abbildungen von Gebieten, deren Rander von beschrankter Drehung Sind. Ann. Acad. Sci. Eenn. Ser. A 1931, 33, 1–77. [Google Scholar]
- Pinchuk, B. Functions with bounded boundary rotation. Isr. J. Math. 1971, 10, 7–16. [Google Scholar] [CrossRef]
- Goodman, A.W. Univalent Functions; Polygonal Publishing Hours: Washingtion, NJ, USA, 1983; Volume 1 and 2. [Google Scholar]
- Janowski, B.W. Some extremal problems for certain families of analytic functions I. Ann. Polon. Math. 1973, 28, 297–326. [Google Scholar] [CrossRef]
- Padmanabhan, K.S.; Parvatham, R. Properties of a class of functions with bounded boundary rotation. Ann. Polon. Math. 1975, 31, 311–323. [Google Scholar] [CrossRef]
- Robertson, M.S. Variational formulas for several classes of analytic functions. Math. Z. 1976, 118, 311–319. [Google Scholar] [CrossRef]
- Sălăgean, G.S. Subclasses of Univalent Functions; Lecture Notes in Mathematics; Springer: Berlin/Heidelberg, Germany, 1983; Volume 1013, pp. 362–372. [Google Scholar]
- Ruscheweyh, S. New criteria for univalent Functions. Proc. Am. Math. Soc. 1975, 49, 109–115. [Google Scholar] [CrossRef]
- Morais, J.; Zayed, H.M. Applications of differential subordination and superordination theorems to fluid mechanics involving a fractional higher-order integral operator. Alex. Eng. J. 2021, 60, 3901–3914. [Google Scholar] [CrossRef]
- Aleman, A.; Constantin, A. Harmonic maps and ideal fluid flows. Arch. Ration. Mech. Anal. 2012, 204, 479–513. [Google Scholar] [CrossRef]
- Branges, L. A proof of the Bieberbach conjecture. Acta Math. 1985, 154, 137–152. [Google Scholar] [CrossRef]
- El-Deeb, S.M.; Cătaş, A. Some inequalities for certain p-valent functions connected with the combination binomial series and confluent hypergeometric function. Axioms 2022, 11, 631. [Google Scholar] [CrossRef]
- Rainville, E.D. Special Functions; The Macmillan Co.: New York, NY, USA, 1960. [Google Scholar]
- Porwal, S.; Kumar, S. Confluent hypergeometric distribution and its applications on certain classes of univalent functions. Afr. Mat. 2017, 28, 1–8. [Google Scholar] [CrossRef]
- Porwal, S. Confluent hypergeometric distribution and its applications on certain classes of univalent functions of conic regions. Kyungpook Math. J. 2018, 58, 495–505. [Google Scholar]
- El-Deeb, S.M. On unified subclass of complex order connected with q-confluent hypergeometric distribution. Surv. Math. Appl. 2022, 16, 327–337. [Google Scholar]
- El-Deeb, S.M.; El-Matary, B.M. Subclasses of bi-univalent functions associated with q-confluent hypergeometric distribution based upon the Horadam polynomials. Adv. Theory Nonlinear Anal. Appl. 2021, 5, 82–93. [Google Scholar] [CrossRef]
- Aouf, M.K. A generalization of functions with real part bounded in the mean on the unit disc. Math. Jpn. 1988, 33, 175–182. [Google Scholar]
- Patil, D.A.; Thakare, N.K. On convex hulls and extreme points of p-valent starlike and convex classes with applications. Bull. Math. Soc. Sci. Math. R. S. Roum. (N. S.) 1983, 27, 145–160. [Google Scholar]
- Owa, S. On certain classes of p-valent functions with negative coefficient. Simon Stevin 1985, 59, 385–402. [Google Scholar]
- Aouf, M.K. On a class of p-valent close-to-convex functions. Int. J. Math. Math. Sci. 1988, 11, 259–266. [Google Scholar] [CrossRef]
- Paatero, V. Uber Gebiete von beschrankter Randdrehung. Ann. Acad. Sci. Fenn. Ser. A 1933, 37, 9. [Google Scholar]
- Alb Lupaş, A.; Oros, G.I. Subordination Results on the q-Analogue of the Sălăgean differential operator. Symmetry 2022, 14, 1744. [Google Scholar] [CrossRef]
- Alb Lupaş, A.; Oros, G.I. Differential sandwich theorems involving Riemann-Liouville fractional integral of q-hypergeometric function. AIMS Math. 2023, 8, 4930–4943. [Google Scholar] [CrossRef]
- Noor, K.I.; Noor, M.A.; Al-Saidb, E. On multivalent functions of bounded radius rotations. Appl. Math. Lett. 2011, 24, 1155–1159. [Google Scholar] [CrossRef]
- Noor, K.I.; Malikz, B.; Mustafa, S. A survey on functions of bounded boundary and bounded radius rotation. Appl. Math. E-Notes 2012, 12, 136–152. [Google Scholar]
- Hussain, S.; Ahmad, K. On strongly starlike and strongly convex functions with bounded radius and bounded boundary rotation. J. Inequal. Appl. 2020, 2020, 126. [Google Scholar] [CrossRef]
- Miller, S.S.; Mocanu, P.T. Second order differential inequalities in the complex plane. J. Math. Anal. Appl. 1978, 65, 289–305. [Google Scholar] [CrossRef]
- Miller, S.S. Differential inequalities and Caratheodory function. Bull. Am. Math. Soc. 1975, 8, 79–81. [Google Scholar] [CrossRef]
- Ruscheweyh, S.; Singh, V. On certain extermal problems for functions with positive real part. Proc. Am. Math. Soc. 1976, 61, 329–334. [Google Scholar] [CrossRef]
- Ruscheweyh, S.; Shiel-Small, T. Hadmard product of schlicht functions and Polya-Schoenberg conjecture. Comment. Math. Helv. 1973, 48, 119–135. [Google Scholar] [CrossRef]
- Choi, J.H.; Saigo, M.; Srivastava, H.M. Some inclusion properties of a certain family of integral operators. J. Math. Anal. Appl. 2002, 276, 432–445. [Google Scholar] [CrossRef]
- Abd El-Hamid, H.A.; Rezk, H.M.; Ahmed, A.M.; AlNemer, G.; Zakarya, M.; El Saify, H.A. Dynamic inequalities in quotients with general kernels and measures. J. Funct. Spaces 2020, 2020, 5417084. [Google Scholar] [CrossRef]
- Ahmed, A.M.; Saker, S.H.; Kenawy, M.R.; Rezk, H.M. Lower bounds on a generalization of Cesaro operator on time scale. Dyn. Contin. Discret. Impuls. Syst. Ser. Math. Anal. 2021, 28, 345–355. [Google Scholar]
- Saker, S.H.; Rezk, H.M.; Abohela, I.; Baleanu, D. Refinement multidimensional dynamic inequalities with general kernels and measures. J. Inequal. Appl. 2019, 2019, 306. [Google Scholar] [CrossRef]
- Li, Y.; Vijaya, K.; Murugusundaramoorthy, G.; Tang, H. On new subclasses of bi-starlike functions with bounded boundary rotation. AIMS Math. 2020, 5, 3346–3356. [Google Scholar] [CrossRef]
- Breaz, D.; Sharma, P.; Sivasubramanian, S.; El-Deeb, S.M. On a new class of bi-close-toconvex functions with bounded boundary rotation. Mathematics 2023, 11, 4376. [Google Scholar] [CrossRef]
- Vijaya, K.; Murugusundaramoorthy, G.; Yalçın, S. Certain class of analytic functions involving Sălăgean type q-difference operator. Konuralp J. Math. 2018, 6, 264–271. [Google Scholar]
- Naeem, M.; Hussain, S.; Mahmood, T.; Khan, S.; Darus, M. A new subclass of analytic functions defined by using Sălăgean q-differential operator. Mathematics 2019, 7, 458. [Google Scholar] [CrossRef]
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content. |
© 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).