Abstract
In this paper, the harmonic function related to the q-Srivastava–Attiya operator is described to introduce a new class of complex harmonic functions that are orientation-preserving and univalent in the open-unit disk. We also cover some important aspects such as coefficient bounds, convolution conservation, and convexity constraints. Next, using sufficiency criteria, we calculate the sharp bounds of the real parts of the ratios of harmonic functions to their sequences of partial sums. In addition, for the first time some of the interesting implications of the q-Srivastava–Attiya operator in harmonic functions are also included.
Keywords:
analytic functions; univalent; harmonic; harmonic starlike functions; convolution; q-differential operators; q-Srivastava–Attiya operator MSC:
30C50; 30C45
1. Introduction and Preliminaries
Minimal surfaces have been represented for a long time using planar harmonic univalent mappings. Such mappings, for instance, were employed in 1952 by Heinz [1] to investigate the Gaussian curvature of nonparametric minimum surfaces over the unit disc (see [2]). Applications for these mappings and associated functions can be found in a wide range of applied mathematical disciplines, including engineering, physics, electronics, medicine, operations research, aerodynamics, and other fields. Harmonic and meromorphic functions, for instance, are essential to the resolution of many physical issues, including the diffusion of salt through a channel, the flow of water through an underground aquifer, the steady-state temperature distribution, and the intensity of the electrostatic field. Harmonic univalent mappings are closely related to each other. Another significant distinction is the ability to create a harmonic univalent mapping on a border interval of the open unit disc. It is common knowledge that if has continuous partial derivatives, then f is only analytic if and when the Cauchy–Riemann equations and are met. Every analytic function is, therefore, a complex-valued harmonic function. Not all complex-valued harmonic functions, however, are analytic since the Cauchy–Riemann equations must be used to link them, as no two solutions to the Laplace equation can be interpreted as the components u and v of an analytic function in of any simply connected domain. A harmonic function’s analytical function might not be harmonic. As an illustration, x is harmonic, but is not. Furthermore, a harmonic function does not always have a harmonic inverse. The linear mapping with is the most basic example of a harmonic univalent function that need not be conformal. Another straightforward example is , which maps harmonically onto a region inside a hypocycloid of three cusps.
Let be continuous and complex harmonic function in the complex domain whenever and real and harmonic in In of any simply connected domain, we uniquely represent where and are analytic in We say is an analytic part and a co-analytic part of Also, is locally univalent and makes sense in only if in (see [3]). Symbolize by the family of functions of the form
which are harmonic, univalent and sense-preserving in the open unit disc so that is normalized by Then, for and are analytic functions () in given by:
and is then written as:
We annotate the family if Denote by the subfamily of consisting of harmonic functions defined by
For the class of harmonic functions with negative coefficients, see [4]. For assumed as in (1) and assumed by
we evoke the Hadamard product (or convolution) of and by
The subclass includes all functions with so Clunie and Sheil-Small also considered starlike functions in denote by The subclass of all starlike functions in can be denoted by . Starlikeness is not a hereditary property for harmonic mappings, so the image of every subdisk is not necessarily starlike with respect to the origin [5,6]. Thus, we need a property to explain the starlikeness of a map in a hereditary form. We have the following definition.
Definition 1
([5]). A harmonic mapping f with is said to be fully starlike if it maps every circle in a one-to-one manner onto a curve that bounds a starlike domain with respect to the origin.
For the family of fully starlike functions is denoted by In 1980, Mocanu gave a relation between fully starlikeness and a differential operator of a non-analytic function [7]. Let
and clearly
Let be a complex-valued function such that for all and in and
Then, f is univalent and fully starlike in However, a fully-starlike mapping need not be univalent [8]. We restrict our discussion to the class. The harmonic function is not fully starlike [5], thus Clunie and SheilSmall [3] posed the following harmonic analogues of the Bieberbach conjecture (see Conjecture 2.3) for the family :
- 1.
- 2.
- 3.
Also, maps onto the half plane; then, for , we have the bounds
which are sharp. The results of these types have been previously obtained only for functions in the special subclass of covex harmonic functions (see [9]). However, necessary coefficient conditions for functions in were also found in [3]. Another challenging area is the Riemann Mapping Theorem related to the harmonic univalent mappings. The best possible Riemann Mapping Theorem was obtained by Hengartner and Schober in [10]. However, the uniqueness problem of mappings in their theorem and also the radius of starlikeness for starlike mappings in are still open. Since it is difficult to directly prove several results or obtain sharp estimates for the families and one usually attempts to investigate them for various subclasses of these families. In this article, we also made an attempt to define new class based on the q-difference Hurwitz–Lerch operator.
q-Difference Hurwitz–Lerch Operator: We aptly evoke the concept of q-operators. The q-difference operator has fascinated and inspired many scientists due to its use in various areas of quantitative sciences. The application of q-calculus was initiated by Jackson [11] (see also [12,13,14,15]. Kanas and Răducanu [16] used fractional q-calculus operators when investigating certain classes of functions, which are analytic in
For the Jackson q-derivative function, is given by the following definition [11]:
and From (7), we have where is sometimes called the basic number n. If . For a function we obtain and
where is the ordinary derivative.
For the first time, a research paper was presented in conjunction with function theory and q-theory by Ismail et al. [17]. So far, only insignificant interest has been shown in this area, although it deserves more attention. Difference operator: q-related to the q-calculus was introduced by Andrews et al. (see [18] Chapter 10), Srivastava [19] and references cited therein. Several interesting properties and characteristics of the Hurwitz–Lerch Zeta (HLZ) function, , defined by (cf. e.g., [20], p. 121), can also be found in recent investigations by Choi and Srivastava [21], Ferreira and Lopez [22], Garg et al. [23], Lin and Srivastava [24], Lin et al. [25] and others. Furthermore, Srivastava and Attiya [26], Raducanu and Srivastava [27] and Prajapat and Goyal [28] and references cited therein have studied various subclasses of analytic functions based on HLZ functions.
In the following, we recall a general q-analogue of Hurwitz–Lerch Zeta function defined in [29],
where, as usual, Now we state the linear operator:
defined, in terms of the Hadamard product (or convolution), by
where, for convenience,
It is easy to observe from (9) and (10) that, for of the form (2), we have
where (and throughout this paper, unless otherwise mentioned) the parameters are constrained as follows:
For and
For various choices of , we obtain different operators, which are listed below (see also [20,30,31]).
which is closely related to some multiplier transformation studied by Fleet [32]. Motivated by the study on harmonic univalent functions [4,33,34,35,36,37,38,39,40,41], for the determination of this article, we will first become acquainted with the new operator (the q-Srivastava–Attiya operator)
and describe a subclass of symbolized , which contains convolution (6) and consists of all functions of the form (1) such that they satisfy inequality:
where and where Also denote
We deem it appropriate to comment underneath some of the function classes that transpire from the function class defined above. Indeed, we observe that if we fix the parameters suitably, We denote the reliable reducible new classes of , which have not been studied so far in association with the q-Srivastava–Attiya operator, as illustrated below:
Remark 1.
(i) If , we let which satisfies
(ii) If , we let satisfying the criteria
(iii) When , let which satisfies
(iv) When we let , satisfying the criteria
(v) When and taking we let , satisfying the criteria
Started by prior papers (see [3,4,34,35,36,37,38,39,40,41]) on the subject of harmonic functions, in this study, we obtain a sufficiency criterion for functions given by (3) to be in the class It is shown that this criterion is also necessary for Furthermore, distortion limits and convexity conditions, extreme points, and partial sum problems are also obtained. The special cases of our results yield the corresponding results for the function classes given in Remark 1.
2. The Coefficient Bounds
We will denote
throughout our study unless otherwise stated.
In the following theorem, we obtain a sufficient criterion for
Theorem 1.
Proof.
In order to achieve the result, it is sufficient to determine whether validates the relationship (21). From (19), we can write
where
Considering the fact that if and only if it suffices to show that
Substituting for and in (22), wehave
The above condition is non-negative by (21), and so □
The harmonic function
where , shows that the coefficient the bound in (21) is sharp. Then, as in (23) and because
The following theorem states that such coefficient restrictions cannot be further improved.
Theorem 2.
For and if and only if
Proof.
Since we only need to prove the “only if” part of the theorem. To this end, for of the form (4), we state that the condition
Equivalently,
The above mandatory condition must hold for all values of z in Upon taking the values of on the positive real axis where we must have
If the condition (24) does not hold, then the numerator in (25) is negative for r close enough to 1. Thus, there exists in (0, 1) for which the proportion (25) is negative. This is contrary to a necessary condition for . This completes the proof of the theorem. □
3. Distortion Bounds and Extreme Points
The subsequent theorem provides the distortion limits for functions in , which yields a covering result for the class
Theorem 3.
Proof.
We will show the right-hand inequality only by taking the absolute value
The proof of the left-hand inequality follows on lines similar to that of the right-hand side’s inequality. □
The covering result follows from the left hand inequality given in Theorem 3.
Theorem 4.
Proof.
Using the left inequality of Theorem 3 and letting we prove that
□
For any compact family, the maximum or minimum of the real part of any continuous linear functional occurs at one of the extreme points of the closed convex hull. Since convex families, we will use the necessary and sufficient coefficient inequalities of Theorems 1 and 2 to determine their extreme points. Next, we regulate the extreme points of closed convex hulls of symbolized by
Theorem 5.
A function if and only if
where
In particular, the extreme points of are and
Proof.
We annotate that for , as in the above theorem, we may state
Then,
and so
Conversely, suppose that Setting
and
Therefore, can be rewritten as
□
4. Inclusion Results
Now, we inspect convinced closure properties for below convex combinations and integral transform.
Theorem 6.
The family is closed under convex combinations.
Proof.
For suppose that where
Then, by Theorem 2
For , , the convex combination of may be written as
Using the inequality (24), we obtain
and therefore □
Now, let the generalized q-Bernardi–Libera–Livingston integral operator be defined by
Theorem 7.
Let Then,
Proof.
From the representation of , it follows that
Using the inequality (24), we obtain
Hence, by Theorem 2, □
Theorem 8.
For let and Then,
Proof.
Let and . Then, is given by (6).
For , we note that and Now, by Theorem 2, we have
and since
and by Theorem 2, we obtain the desired result. □
5. Partial Sums Results
Many researchers have studied and distinguished partial sum results for different classes of analytic functions based on the results provided by Silvia [42]. Silverman [43] determined that the lower bounds on ratios like or have been found to be sharp only when The lower bounds in question are strictly increasing functions of Analogous results on harmonic functions have not yet been explored in the literature. Recently, in [44], Porwal filled this gap by checking exciting results on partial sums of star harmonic univalent functions (see [45]). In this section, we examine partial sum results for
Let consisting of functions , as assumed as in (3) with
where
unless otherwise stated. Now, we discuss the ratio of , as assumed as in (3) with , where
We begin by obtaining the sharp bounds for
Theorem 9.
If of the form (3) with and holds (30), then
The result (31) is sharp for
Proof.
To prove (31) we set
It suffices to show that Now, from (33) we can write
Hence, we obtain
Now, if
From the condition (30), it is sufficient to show that
which is equivalent to
To see that as in (32) gives the sharp result, we observe that for
□
We next determine bounds for
Theorem 10.
The result (34) is sharp for
Proof.
To prove (34) we let
Hence, we obtain
The last inequality is equivalent to
Making use of (30) and (35), we obtain (5). Finally, equality (34) holds for as in (36). □
We next turn to ratios for the for and .
Theorem 11.
The result (37) is sharp for
Proof.
To prove (37) we define
The result (37) follows by using the techniques used in Theorem 9. □
Proceeding exactly as in the proof of Theorem 10, we can prove the following theorem.
Corollary 1.
If of the form (3) with and satisfies (30), then
The result is sharp for
We next determine bounds for and
Corollary 2.
The result (39) is sharp for
Theorem 12.
The result (40) is sharp for
Proof.
To prove (40) we set
We omit the details of this proof because it runs parallel to that from Theorem 10. □
Corollary 3.
The result (41) is sharp for
Corollary 4.
Corollary 5.
If of the form (3) with and satisfies (30), then
Corollary 6.
If of the form (3) with and holds (30), then
The result (44) is sharp for
Corollary 7.
The result (45) is sharp for
Corollary 8.
If of the form (3) with satisfies (30), then
The result (46) is sharp for
6. Integral Means Inequalities
An analytic function h is subordinate to an analytic function written provided there is an analytic function w defined on with and sustaining . Using the principle of subordination and the following Lemma 1, we obtain integral means inequalities for the functions in the family due to Dziok [36] and Silverman [46].
Lemma 1
([47]). If the functions ϕ and ψ are analytic in with ( ψ is subordinate to ψ), then for and
Due to the recent work of Dziok [36], we suppose and is defined by
where is given by (26). Since
by Lemma 1, we have
Thus, we have the following result:
Lemma 2.
Let Then,
where and are defined by (27) and (28).
By Lemma 13 and Theorem 5, we have the following:
Theorem 13.
Let Then,
where and are defined by (27) and (28).
7. Conclusions
For a suitable choice of , when we break through with and the many results which exist in this paper motivate the expansion and simplification of the earlier simpler classes of harmonic functions (see [39,40,41]) associated with the q-Srivastava–Attiya operator. Correspondingly, setting can provide interesting results for Noshiro-type harmonic functions based on the q-Srivastava–Attiya operator. The facts convoluted in the beginnings of such a specialization of meaning (see (14)–(17)), as were obtained in this article, are relatively straightforward and therefore omitted. Utilizing the principles of quantum calculus and connecting Hurwitz–Lerch zeta functions of certain meromorphic and harmonic functions, the study undertaken in this article can be extended to investigate necessary and sufficient conditions, problems for partial sums, distortion limits, convexity conditions, and convolution preservation and its implications. Finally, many problem remain open, and it may be interesting to extend the obtained results in this article. Furthermore, it may be interesting to characterize the domain as open and bounded to define a deferential operator applicable to differential equations, or a partial deferential in finite or infinite Banach and Hilbert spaces or in general in Sobolev space, for example. Or the Srivastava–Attiya operator can be extended to the domain of control system analysis where the field of vector space is complex in in some cases for future works, such as in [48]. The operator introduced in this article can also be applied to extend the study on various subclasses of bi-univalent functions, meromorphic functions and symmetric functions [49,50,51,52]. By using the Miller–Ross-type Poisson distribution series (see [53] and references cited therein), one can also study certain inclusion results for
Author Contributions
Conceptualization, G.M., K.V., D.B. and L.-I.C.; methodology, G.M., K.V., D.B. and L.-I.C.; validation, G.M., K.V., D.B. and L.-I.C.; formal analysis, G.M., K.V., D.B. and L.-I.C.; investigation, G.M., K.V., D.B. and L.-I.C.; resources, G.M., K.V., D.B. and L.-I.C.; writing—original draft preparation, G.M., K.V., D.B. and L.-I.C.; writing—review and editing, G.M., K.V., D.B. and L.-I.C.; supervision, G.M., K.V., D.B. and L.-I.C.; project administration, G.M., K.V., D.B. and L.-I.C. All authors have read and agreed to the published version of the manuscript.
Funding
This research received no external funding.
Data Availability Statement
The data presented in this study are available on request from the corresponding author.
Conflicts of Interest
The authors declare no conflict of interest.
References
- Heinz, E. Über die Lösungen der Minimalflächengleichung, (German). Nachr. Akad. Wiss. Göttingen. Math.-Phys. Kl. Math.-Phys.-Chem. Abt. 1952, 51–56. [Google Scholar]
- Weitsman, A. On univalent harmonic mappings and minimal surfaces. Pacific J. Math. 2000, 192, 191–200. [Google Scholar] [CrossRef][Green Version]
- Clunie, J.; Sheil-Small, T. Harmonic univalent functions. Ann. Acad. Aci. Fenn. Ser. A.I. Math. 1984, 9, 3–25. [Google Scholar] [CrossRef]
- Silverman, H. Harmonic univalent functions with negative coefficients. J. Math. Anal. Appl. 1998, 220, 283–289. [Google Scholar] [CrossRef]
- Ahuja, O.P.; Jahangiri, J.M. On a linear combination of classes of multivalently harmonic functions. Kyungpook Math. J. 2002, 42, 61–67. [Google Scholar]
- Abu-muhanna, Y. On harmonic univalent functions. Complex Variables Theory Appl. 1999, 39, 341–348. [Google Scholar] [CrossRef]
- Ahuja, O.P.; Jahangiri, J.M. Sakaguchi-type harmonic univalent functions. Sci. Math. Jpn. 2004, 59, 163–168. [Google Scholar]
- Abu-muhanna, Y.; Lyzzaik, A. The boundary behaviour of harmonic univalent maps. Pacific J. Math. 1990, 141, 1–2. [Google Scholar] [CrossRef]
- Wang, X.-T.; Liang, X.-Q.; Zhang, Y.-L. Precise coefficient estimates for close-to-convex harmonic univalent mappings. J. Math. Anal. Appl. 2001, 263, 501–509. [Google Scholar] [CrossRef]
- Hengartner, W.; Schober, G. Harmonic mappings with given dilatation. J. London Math. Soc. 1986, 33, 473–483. [Google Scholar] [CrossRef]
- Jackson, F.H. On q-functions and a certain difference operator. Trans. R. Soc. Edinb. 1908, 46, 253–281. [Google Scholar] [CrossRef]
- Amini, E.; Al-Omari, S.; Nonlaopon, K.; Baleanu, D. Estimates for coefficients of bi-univalent functions associated with a fractional q-difference operator. Symmetry 2022, 14, 879. [Google Scholar] [CrossRef]
- Aral, A.; Gupta, V.; Agarwal, R.P. Applications of q-Calculus in Operator Theory; Springer: New York, NY, USA, 2013. [Google Scholar]
- Trjitzinsky, W.J. Analytic theory of linear q-difference equations. Acta Math. 1933, 61, 1–38. [Google Scholar] [CrossRef]
- Kiryakova, V. Generalized Fractional Calculus and Applications; Pitman Research Notes in Mathematics; Longman Scientific and Technical: Harlow, UK, 1993; Volume 301. [Google Scholar]
- Kanas, S.; Răducanu, D. Some subclass of analytic functions related to conic domains. Math. Slovaca 2014, 64, 1183–1196. [Google Scholar] [CrossRef]
- Ismail, M.E.H.; Merkes, E.; Styer, D. A generalization of starlike functions. Complex Var. Theory Appl. 1990, 14, 77–84. [Google Scholar] [CrossRef]
- Andrews, G.E.; Askey, G.E.; Roy, R. Special Functions; Cambridge University Press: Cambridge, UK, 1999. [Google Scholar]
- Srivastava, H.M. Operators of basic (or q-) calculus and fractional q-calculus and their applications in geometric function theory of complex analysis. Iran. J. Sci. Technol. Trans. A Sci. 2020, 44, 327–344. [Google Scholar] [CrossRef]
- Srivastava, H.M.; Choi, J. Series Associated with the Zeta and Related Functions; Kluwer Academic Publishers: Dordrecht, The Netherlands, 2001. [Google Scholar]
- Choi, J.; Srivastava, H.M. Certain families of series associated with the Hurwitz-Lerch Zeta function. Appl. Math. Comput. 2005, 170, 399–409. [Google Scholar] [CrossRef]
- Ferreira, C.; Lopez, J.L. Asymptotic expansions of the Hurwitz-Lerch Zeta function. J. Math. Anal. Appl. 2004, 298, 210–224. [Google Scholar] [CrossRef]
- Garg, M.; Jain, K.; Srivastava, H.M. Some relationships between the generalized Apostol-Bernoulli polynomials and Hurwitz-Lerch Zeta functions. Integral Transform. Spec. Funct. 2006, 17, 803–815. [Google Scholar] [CrossRef]
- Lin, S.-D.; Srivastava, H.M. Some families of the Hurwitz-Lerch Zeta functions and associated fractional derivative and other integral representations. Appl. Math. Comput. 2004, 154, 725–733. [Google Scholar] [CrossRef]
- Lin, S.-D.; Srivastava, H.M.; Wang, P.-Y. Some espansion formulas for a class of generalized Hurwitz-Lerch Zeta functions. Integral Transform. Spec. Funct. 2006, 17, 817–827. [Google Scholar] [CrossRef]
- Srivastava, H.M.; Attiya, A.A. An integral operator associated with the Hurwitz-Lerch Zeta function and differential subordination. Integral Transform. Spec. Funct. 2007, 18, 207–216. [Google Scholar] [CrossRef]
- Raducanu, D.; Srivastava, H.M. A new class of analytic functions defined by means of a convolution operator involving the Hurwitz-Lerch Zeta function. Integral Transform. Spec. Funct. 2007, 18, 933–943. [Google Scholar] [CrossRef]
- Prajapat, J.K.; Goyal, S.P. Applications of Srivastava-Attiya operator to the classes of strongly starlike and strongly convex functions. J. Math. Inequal. 2009, 3, 129–137. [Google Scholar] [CrossRef]
- Shah, S.A.; Noor, K.I. Study on the q-analogue of a certain family of linear operators. Turk. J. Math. 2019, 43, 2707–2714. [Google Scholar] [CrossRef]
- Hiba, F.A.; Ghanim, F.; Agarwal, P. Geometric studies on inequalities of harmonic functions in a Complex Field Based on ℵ-generalized Hurwitz-Lerch Zeta function. Iran. J. Math. Sci. Inform. 2023, 1, 73–95. [Google Scholar]
- Noor, K.I.; Riaz, S.; Noor, M.A. On q-Bernardi integral operator. TWMS J. Pure Appl. Maths. 2017, 8, 3–11. [Google Scholar]
- Flett, T.M. The dual of an inequality of Hardy and Littlewood and some related inequalities. J. Math. Anal. Appl. 1972, 38, 746–765. [Google Scholar] [CrossRef]
- Ahuja, O.P. Planar harmonic univalent and related mappings. J. Inequal. Pure Appl. Math 2005, 6, 1–18. [Google Scholar]
- Ahuja, O.P.; Jahangiri, J. Noshiro-type harmonic univalent functions. Sci. Math. Jpn. 2002, 56, 1–7. [Google Scholar]
- Silverman, H.; Silvia, E.M. Subclasses of harmonic univalent functions. N. Z. J. Math. 1999, 28, 275–284. [Google Scholar]
- Dziok, J. On Janowski harmonic functions. J. Appl. Anal. 2015, 21, 99–107. [Google Scholar] [CrossRef]
- Jahangiri, J.M.; Silverman, H. Harmonic univalent functions with varying rrguments. Internat. J. Appl. Math. 2002, 8, 267–275. [Google Scholar]
- Jahangiri, J.M. Harmonic functions starlike in the unit disc. J. Math. Anal. Appl. 1999, 235, 470–477. [Google Scholar] [CrossRef]
- Totoi, A.E.; Cotîrlă, L.I. Preserving Classes of Meromorphic Functions through Integral Operators. Symmetry 2022, 14, 1545. [Google Scholar] [CrossRef]
- Jahangiri, J.M.; Murugusundaramoorthy, G.; Vijaya, K. Salagean-Type harmonic univalent functions. Southwest J. Pure Appl. Math. 2002, 2, 77–82. [Google Scholar]
- Jahangiri, J.M.; Murugusundaramoorthy, G.; Vijaya, K. Classes of harmonic starlike functions defined by Sălăgean-type q-differential operators. Hacet. J. Math. Stat. 2020, 49, 416–424. [Google Scholar] [CrossRef]
- Silvia, E.M. On partial Sums of convex functions of order α. Houst. J. Math. 1985, 3, 397–404. [Google Scholar]
- Silverman, H. Partial sums of starlike and convex functions. J. Math. Anal. Appl. 1997, 209, 221–227. [Google Scholar] [CrossRef]
- Porwal, S. Partial sums of certain harmonic univalent functions. Lobachevskii J. Math. 2011, 32, 366–375. [Google Scholar] [CrossRef]
- Porwal, S.; Dixit, K.K. Partial sums of starlike harmonic univalent functions. Kyungpook Math. J. 2010, 50, 433–445. [Google Scholar] [CrossRef]
- Silverman, H. Integral means for univalent functions with negative coefficients. Houston J. Math. 1997, 23, 169–174. [Google Scholar]
- Littlewood, J.E. On inequalities in theory of functions. Proc. Lond. Math. Soc. 1925, 23, 481–519. [Google Scholar] [CrossRef]
- Rekkab, S.; Benhadid, S.; Al-Saphory, R. An Asymptotic Analysis of the Gradient Remediability Problem for Disturbed Distributed Linear Systems. Baghdad Sci. J. 2022, 19, 1623–1635. [Google Scholar] [CrossRef]
- Al-shbeil, I.; Gong, J.; Shaba, T.G. Coefficients Inequalities for the bi-univalent functions related to q-Babalola convolution operator. Fractal Fract. 2023, 7, 155. [Google Scholar] [CrossRef]
- Srivastava, H.M.; Al-Shbeil, I.; Xin, Q.; Tchier, F.; Khan, S.; Malik, S.N. Faber polynomial coefficient estimates for bi-close-to-convex functions defined by the q-fractional derivative. Axioms 2023, 12, 585. [Google Scholar] [CrossRef]
- Faisal, M.I.; Al-Shbeil, I.; Abbas, M.; Arif, M.; Alhefthi, R.K. Problems Concerning Coefficients of Symmetric Starlike Functions Connected with the Sigmoid Function. Symmetry 2023, 15, 1292. [Google Scholar] [CrossRef]
- Al-Shbeil, I.; Gong, J.; Ray, S.; Khan, S.; Khan, N.; Alaqad, H. The properties of meromorphic multivalent q-starlike functions in the Janowski domain. Fractal Fract. 2023, 7, 438. [Google Scholar] [CrossRef]
- Sümer Eker, S.; Murugusundaramoorthy, G.; Şeker, B.; Çekiç, B. Spiral-like functions associated with Miller–Ross-type Poisson distribution series. Bol. Soc. Mat. Mex. 2023, 29, 16. [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/).