analytic functions
در نشریات گروه ریاضی-
International Journal Of Nonlinear Analysis And Applications, Volume:16 Issue: 7, Jul 2025, PP 37 -46
In this paper, we extend the $q$-derivative operator, which plays an essential role in quantum calculus. Indeed, by using the Hadamard product and generalized Koebe function we define the following $(\alpha,\beta,\gamma)$-derivative operator\begin{equation*} {\rm d}_{\alpha,\beta,\gamma} f(z)=\frac{1}{z}\left\{f(z)*\mathfrak{L}_{\alpha,\beta,\gamma}(z)\right\},\end{equation*}where\begin{equation*} \mathfrak{L}_{\alpha,\beta,\gamma}(z)=\frac{2(1-\gamma)z}{(1-\alpha z)(1-\beta z)},\end{equation*}and $\alpha\in[-1,1]$, $\beta\in[-1,1]$, $\alpha\beta\neq \pm1$ and $\gamma\in[0,1)$. Then by subordination relation, the operator ${\rm d}_{\alpha,\beta,\gamma} f(z)$, and a special function $\phi_\delta(z)=1+\delta z/\exp(\delta z)$ ($0<\delta\leq1$), we define a new particular Ma-Minda class. We investigate some properties of this class, such as, radius problem and coefficient estimate.
Keywords: Unit Disk, Analytic Functions, Starlike Function, Subordination, Radius Problems, Coefficients Problems -
International Journal Of Nonlinear Analysis And Applications, Volume:16 Issue: 5, May 2025, PP 77 -85We provide new sharp results on the action of Toeplitz operators from Triebel and Besov spaces to new BMOA-type function spaces on the unit disk. In this paper, we consider $s\geq1$ case in previous papers $s<1$ was covered for $BMOA_{s,q}$ and $BMOA_s^p$ spaces. We modify a little our previously known proofs.Keywords: Toeplitz Operators, Besov Type Spaces, Lizorkin-Triebel Type Spaces, Analytic Functions
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International Journal Of Nonlinear Analysis And Applications, Volume:15 Issue: 8, Aug 2024, PP 53 -64In this investigation, using Opoola differential operator ($D^{m}(\mu,\beta,t)f(z)$), a new integral operator: $I_{t,\beta,\mu}^{m,\sigma}(f_{1},...,f_{n})(z): A^{n}\rightarrow A$ is defined in the unit disk, $U=\left\lbrace z\in C:\left|z\right|<1\right\rbrace$; and we investigated the Univalence conditions of this generalized operator. Finally, a number of corollaries and remarks which show the extension of our results are presented.Keywords: Analytic Functions, Univalent Functions Starlike Functions, Convex Functions, Close-To-Convex Functions, Integral Operator
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فرض کنیم $\mathcal{S}^{\ast}(f_c)$ خانواده ای از توابع تحلیلی $f(z)=z+a_2z^2+a_3z^3+\cdots$ در دیسک واحد باز $\mathbb{D}$ باشند که برای $c\in (0,1)$، در رابطه ی زیر صدق می کنند:$$\frac{zf'(z)}{f(z)}\prec f_c(z)=\frac{1}{\sqrt{1-cz}}, \quad z\in\mathbb{D}.$$ابتدا، توابع تحلیلی $f_c(z)$ را معرفی کرده و ویژگی ستاره گونی و مثبت بودن قسمت حقیقی آن ها را بررسی می کنیم، و سپس نگاره ی آنها در دیسک واحد باز $\mathbb{D}$، که بیضی های کاسینی می باشند، را به دست می آوریم. بیضی های کاسینی به دلیل ویژگی هایی که دارند، برای حل مسایل گوناگونی در حوزه های مانند هندسه، فیزیک و ریاضیات، کاربرد دارند. این منحنی ها در بررسی حرکت موج ها و امواج الکترومغناطیسی در فضاهای بین ستاره ای و نیز در طراحی سازه های مهندسی مانند تلسکوپ ها، به کار می روند. در این مقاله به کمک انتگرال، ساختار نگاشت ها در این خانواده و برخی خواص شامل بیشینه و کمینه قدرمطلق، و کران های قسمت حقیقی این توابع را، بررسی می کنیم. همچنین روابط بین رده های هندسی تعریف شده با این خانواده، که شامل مرتبه ستاره گونی و مرتبه به طور قوی ستاره گونی می باشند، را به دست می آوریم.
کلید واژگان: وابع تحلیلی، توابع ستاره گون، توابع به طور قوی ستاره گون، بیضی کاسینیLet's denote $\mathcal{S}^{\ast}(f_c)$ as a family of analytic functions $f(z)=z+a_2z^2+a_3z^3+\cdots$ in the open unit disk $\mathbb{D}$ that satisfy the following relation for $c\in (0,1)$:$$\frac{zf'(z)}{f(z)}\prec f_c(z)=\frac{1}{\sqrt{1-cz}}, \quad z\in\mathbb{D}.$$First, we introduce the analytic functions $f_c(z)$ and examine their starlike and positivity properties of the real part. Then, we obtain their images in the open unit disk $\mathbb{D}$, which are Cassini ovals. Cassini ovals, due to their properties, have applications in solving various problems in fields such as geometry, physics, and mathematics. These curves are used in studying the motion of waves and electromagnetic waves in interstellar spaces, as well as in the design of engineering structures such as telescopes. In this article, with the help of integrals, we investigate the structure of mappings in this family and some properties including maximum and minimum moduli, bounds of the real part of these functions. Moreover, we obtain the relationships between the defined geometric ranks with this family, including the order of starlikeness and order of strong starlikeness.
IntroductionLet $\mathcal{A}$ be a set of analytic functions of the form $f(z)=z+a2z^2+a3z^3+\cdots$ in the open unit disc $\mathbb{D}:=\left\{z\in\mathbb{C}\colon |z|<1\right\}$. A function $f\in\mathcal{A}$ is called univalent if it is one-to-one. In [5], two classes of starlike and convex functions with order $0\le \beta<1$ are defined as follows:\begin{equation}\label{starlike-convex}\mathcal{S}^{\ast}(\beta):=\left\{f\in\mathcal{A}\colon \Re\left(\frac{zf'(z)}{f(z)}\right)>\beta\right\},\quad \mathcal{K}(\beta):=\left\{f\in\mathcal{A}\colon zf'(z)\in\mathcal{S}^{\ast}(\beta)\right\}.\end{equation}Similarly, in [2], the class of functions called strongly starlike with order $0<\alpha\le 1$ is defined as:\[\mathcal{SS}^{\ast}(\alpha)=\left\{f\in\mathcal{A}\colon \left|\mathrm{Arg}\frac{zf'(z)}{f(z)}\right|<\frac{\alpha \pi}{2}\right\}.\]If $f$ and $g$ are two analytic functions in $\mathbb{D}$, we say that $f$ is subordinate to $g$ \cite{Dur}, denoted by $f\prec g$, if and only if there exists an analytic function $w$ with $w(0)=0$ such that for all $z\in\mathbb{D}$:\[\left|w(z)\right|<1, \quad f(z)=g(w(z)).\]If $g$ is univalent, we have:\[f(z)\prec g(z) \Longleftrightarrow f(0)=g(0),\quad f(\mathbb{D})\subset g(\mathbb{D}).\]Given $c\in(0,1)$, analytic functions $f_c$ are defined as follows:(1.2)$$f_c(z):=\frac{1}{\sqrt{1-cz}}=1+\frac{c}{2}z+\frac{3c^2}{8}z^2+\cdots$$in the principal branch of the complex logarithm, where $\log 1=0$. These functions are univalent in $\mathbb{D}$ and map the open unit disc $\mathbb{D}$ into the interior of the Cassinian ovals given by the Cartesian equation:\begin{equation}\label{Cassinian-Ovals}(x^2+y^2)^2-\frac{2}{1-c^2}(x^2-y^2)+\frac{1}{1-c^2}=0,\end{equation}or the polar equation:\begin{equation}\label{Cassinian-Ovals1}r^4-\frac{2r^2 }{1-c^2} \cos(2\theta)=\frac{1}{c^2-1}.\end{equation}
Main ResultsIn this section, we will first derive the structure of functions in the class $\mathcal{S}^{\ast}(f_c)$, and then using the stated theorems, we will determine the order of starlikeness and strongly starlikeness of functions in the class $\mathcal{S}^{\ast}(f_c)$. Theorem 2.1. A function $f$ belongs to the class $\mathcal{S}^{\ast}(f_c)$ if and only if there exists a function $p \prec f_c$ such that\begin{equation}\label{thm-1-0}f(z)=z\exp\left(\int_{0}^{z}\frac{p(t)-1}{t}dt\right), \quad z\in\mathbb{D}.\end{equation} If we set $p(z)=f_c(z)$ in theorem (2.1), then we get(2.2) $$F_c(z):=z\exp\left(\int_{0}^{z}\frac{f_c(t)-1}{t}dt\right)=\frac{4z}{(1+\sqrt{1-cz})^2}, \quad z\in\mathbb{D}.$$This function $F_c(z)$ is an extreme function for the class $\mathcal{S}^{\ast}(f_c)$. Figure 2 illustrates the image of the open unit disk $\mathbb{D}$ under the mapping $F_c(z)$ for $c=3/4$. Theorem 2.2. Let $f_c$ be the given function described in (1.2). Then $f_c$ is convex and satisfies the following conditions:\begin{equation}\label{max-min0}\max_{|z|=r<1}\left|f_c(z)\right|=f_c(r),\quad \min_{|z|=r<1}\left|f_c(z)\right|=f_c(-r).\end{equation} In the following theorem, we obtain bounds for the real part and strongly starlike mappings of the functions $f_c$. Theorem 2.3. Suppose $c\in(0,1)$. Then we have the following:(1) \[f_c(\mathbb{D})\subset \left\{w\in\mathbb{C}\colon \frac{1}{\sqrt{1+c}}<\Re(w)<\frac{1}{\sqrt{1-c}}\right\},\](2)\[f_c(\mathbb{D})\subset \left\{w\in\mathbb{C}\colon \left|\mathrm{Arg}(w)\right|<\frac12 \arccos\sqrt{1-c^2}\right\}.\] Theorem 2.4. If $f\in \mathcal{S}^{\ast}(fc)$ and $|z|=r<1$, then the following hold:(1) \[\frac{zf'(z)}{f(z)}\prec \frac{zF'_c(z)}{F_c(z)},\quad \frac{f(z)}{z}\prec\frac{F_{c}(z)}{z},\](2) \[F'_c(-r)\le \left|f'(z)\right|\le F'_c(r),\](3) \[-F_c(-r)\le |f(z)|\le F_c(r),\](4) \[\left|\arg{(f(z)/z)}\right|\le \max{|z|=r}\arg\left(\frac{1}{(1+\sqrt{1-cz})^2}\right),\](5) Either $f$ is a rotation of $F_c$ or\[\left\{w\in \mathbb{C} \colon\ |w|\leq-F_c(-1)=\frac{4}{(1+\sqrt{1+c})^2}\right\}\subsetf(\mathbb{D}),\]where in all cases, the function $F_c$ is defined as per equation (2.2).\end{thm}In the following theorem, we determine the subordination order and strong subordination order for the class of functions $\mathcal{S}^{\ast}(f_c)$. Theorem 2.5. The class of functions $\mathcal{S}^{\ast}(f_c)$ has the following properties:(1) For $0\le \beta\le \frac{1}{\sqrt{1+c}}$, we have\[\mathcal{S}^{\ast}(f_c)\subset \mathcal{S}^{\ast}(\beta).\](2) For $\frac{1}{\pi}\arccos\sqrt{1-c^2}\le \alpha\le 1$, we have\[\mathcal{S}^{\ast}(f_c)\subset \mathcal{SS}^{\ast}(\alpha).\]
ConclusionsThe class $\mathcal{S}^{\ast}(f_c)$ consists of functions that can be represented in a specific form involving the function $f_c$, which is a special function related to the starlikeness property. The function $F_c(z)$, derived from $f_c(z)$, is an extreme function for the class $\mathcal{S}^{\ast}(f_c)$ and has specific properties, including convexity and bounds on its maximum and minimum modulus on the unit circle. The presented theorems provide bounds for the real part of the functions $f_c$ and establish relationships related to subordination and strong subordination order for the class of functions $\mathcal{S}^{\ast}(f_c)$. Overall, the obtained theorems and their proofs contribute to understanding the structural properties, order of starlikeness and strongly starlikeness, as well as subordination order within the class of functions $\mathcal{S}^{\ast}(f_c)$, for different values of the parameter $c$.
Keywords: Analytic functions, Starlike functions, Strongly starlike functions, Cassini Ovals -
In this paper, we investigate the subclasses of harmonic univalent functions introduced by Porwal et al. in 2018. By implementing specific convolution operators such as the Pascal distribution series, we examine the inclusion relations of these functions. Moreover, we investigate several mapping properties involving these subclasses.
Keywords: Analytic functions, Harmonic $, gamma$-uniformly star-like, Pascal distribution series, Univalent functions -
On this study, two new subclasses of the function class $\Xi$ of bi-univalent functions of complex order defined in the open unit disc are introduced and investigated. These subclasses are connected to the Hohlov operator with $(\mathcal {P,Q})-$Lucas polynomial and meet subordinate criteria. For functions in these new subclasses, we also get estimates for the Taylor-Maclaurin coefficients $|a_2|$ and $|a_3|$. The results are also discussed as having a number of (old or new) repercussions.Keywords: Analytic functions, Univalent functions, Bi-univalent functions, Bi-starlike, bi-convex functions, Hohlov operator, Gaussian hypergeometric function, (P, Q)-Lucas polynomial
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The purpose of the paper is to derive some interesting implications associated with some differential inequalities, for certain analytic functions in the open unit disk. Connections to previously well known results are also established.
Keywords: Analytic functions, Subordination, Carathéodory functions -
International Journal Of Nonlinear Analysis And Applications, Volume:14 Issue: 7, Jul 2023, PP 99 -106In this paper, we investigate the Toeplitz determinant for a family of functions with bounded turnings, we give estimates of the Toeplitz determinants of fifth order for the set $\mathcal{R}$ of univalent functions with bounded turnings in the unit disc. Also, we obtain bounds of the fifth Toeplitz determinant for the subclasses of the class $\mathcal{R}$.Keywords: Analytic functions, Univalent functions, Bounded turning functions, Toeplitz determinant
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International Journal Of Nonlinear Analysis And Applications, Volume:14 Issue: 5, May 2023, PP 259 -265The primary motivation of the paper is to give necessary and sufficient condition for the power series distribution (Pascal model) to be in the subclasses $\mathcal{VS}_{p}\left( \vartheta ,\gamma ,\kappa \right) $ and $\mathcal{VC}_p(\vartheta ,\gamma ,\kappa )$ of analytic functions. Further, to obtain certain connections between the Pascal distribution series and subclasses of normalized analytic functions whose coefficients are probabilities of the Pascal distribution.Keywords: Analytic functions, Univalent functions, power series distribution
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International Journal Of Nonlinear Analysis And Applications, Volume:14 Issue: 1, Jan 2023, PP 25 -32In this paper, the classical Fekete-Szego problem is studied regarding a class of univalent functions generated using a generalized fractional differential operator. The results presented in the main theorem are new generalizations for well-known results.Keywords: Analytic functions, fractional operator, Univalent functions, normalized functions, Fekete-Szego problems
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International Journal Of Nonlinear Analysis And Applications, Volume:14 Issue: 1, Jan 2023, PP 3145 -3154In this paper, we introduce a new subclass of the class of \textit{m}-fold symmetric bi-univalent functions and obtain estimates of the Taylor-Maclaurin coefficients $|a_{m+1}|,|a_{2m+1}|$ and Fekete-Szeg\H{o} functional problem for functions in this new subclass. The results in this paper generalize some of the results of Huo Tang et al. [18] Altinkaya and Yalcin [3].Keywords: Analytic functions, Bi-Univalent functions, m-fold symmetric functions, subordination, coefficient estimates, Fekete-Szego problem
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We investigate on some subclasses of analytic fuctions defined by subordination. Also, we give estimates of $\sup_{|z|<1}\big(1-|z|^{2}\big)\big|\dfrac{f^{''}(z)}{f^{'}(z)}\big|$, for functions belonging to extended class of starlike functions. For a locally univalent analytic function $f$ defined on $\Delta =\{z\in \mathbb{C}: |Z|<1\}$, we consider the pre-Schwarzian norm by $\Vert T\Vert=\sup _{|z|<1}\big(1-|z|^{2}\big)\big|\dfrac{f^{''}(z)}{f^{'}(z)}\big|$. In this work, we find the sharp norm estimate for the functions $f$ in the extended classes of starlike functions.
Keywords: Analytic Functions, Starlike functions, Pre-schwarzian derivatives, Subordination -
In this paper, we obtain upper bounds of the initial Taylor-Maclaurin coefficients $\left\vert a_{2}\right\vert ,$ $\left\vert a_{3}\right\vert $ and $\left\vert a_{4}\right\vert $ and of the Fekete-Szegö functional $\left\vert a_{3}-\eta a_{2}^{2}\right\vert $ for certain subclasses of analytic and bi-starlike functions $\mathcal{S}_{\sigma }^{\ast }(\beta,\theta ,n,m)$ in the open unit disk. We have also obtained an upper bound of the functional $\left\vert a_{2}a_{4}-a_{3}^{2}\right\vert $ for the functions in the class $\mathcal{S}_{\sigma }^{\ast }(\beta ,\theta ,n,m)$. Moreover, several interesting applications of the results presented here are also discussed.Keywords: Analytic functions, Univalent functions, Bi-univalent functions, Bi-starlike functions, Subordination between analytic functions, Hankel determinant
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International Journal Of Nonlinear Analysis And Applications, Volume:13 Issue: 2, Summer-Autumn 2022, PP 237 -251
Using the q-calculus operator we defined a new subclass of analytic functions Mq(ϑ,Φ) defined in the open unit disk Δ={z∈C:|z|<1} related with Bernoulli's lemniscate and obtained certain coefficient estimates, Fekete-Szeg\H{o} inequality results for f∈Mq(ϑ,Φ). As a special case of our result, we obtain Fekete-Szeg\H{o} inequality for a class of functions defined through Poisson distribution and further with the help of MAPLE\texttrademark\ software we find Hankel determinant inequality for f∈Mq(ϑ,Φ). Our investigation generalises some previous results obtained in different articles.
Keywords: Analytic functions, differential subordination, Fekete-SzegHo problem, q−calculus operator, Bernoulli's lemniscate -
In this paper, we discuss the upper bounds for the second Hankel determinant 𝐻2(2) of a new subclass of 𝜆-pseudo-starlike bi-univalent functions defined in the open unit disk 𝑈.
Keywords: Analytic functions, Bi-univalent functions, 𝜆- Pseudo-starlike functions, Upper bounds, Second Hankel determinant -
International Journal Of Nonlinear Analysis And Applications, Volume:13 Issue: 1, Winter-Spring 2022, PP 3085 -3092
In this paper, we introduce a new operator Ωc g(z) associated with polylogarithm function, applying it on the subclasses AHΣ∗ B (γ, k) of meromorphic starlike bi-univalent functions of order γ, and AHΣe∗ B (γ, k) of meromorphic strongly starlike bi-univalent functions of order γ, also we find estimates on the coefficients |b0| and |b1| for functions in these subclasses.
Keywords: Analytic functions, univalent functions, Bi-univalent functions, Starlike functions, strongly starlike functions, polylogarithm function, Meromorphic functions, Coefficientestimates -
The purpose of this paper is to define a new class of analytic, normalized functions in the open unit disk D = {z : z ∈ C and |z| < 1} subordinating with crescent shaped regions, and to derive certain coefficient estimates a2 , a3 and Fekete-Szeg¨o inequality for f ∈ Mq(α, β, λ). A similar result have been done for the function f −1 . Further application of our results to certain functions defined by convolution products with a normalized analytic function is given, in particular we obtain FeketeSzeg¨o inequalities for certai
Keywords: Analytic functions, Starlike functions, Convex functions, Subordination, Fekete-Szeg¨o inequality, Poisson distribution series, Hadamard product -
International Journal Of Nonlinear Analysis And Applications, Volume:12 Issue: 1, Winter-Spring 2021, PP 567 -573
In the present paper, we study a new subclass $mathcal{M}_p(alpha,beta)$ of $p$--valent functions and obtain some inequalities concerning the coefficients for the desired class. Also, by using the Hadamard product, we define a new general operator and find a condition such that it belongs to the class $mathcal{M}_p(alpha,beta)$.
Keywords: Analytic functions, p–valent functions, Generalized Bessel function, Gaussianhypergeometric function, Hadamard product -
International Journal Of Nonlinear Analysis And Applications, Volume:12 Issue: 1, Winter-Spring 2021, PP 997 -1008
Using the techniques of the differential subordination and superordination, we derive certain subordination and superordination properties of multivalent functions associated with the Dziok-Srivastava operator.
Keywords: analytic functions, meromorphic functions, multivalent functions, Dziok-Srivastavaoperator, differential subordination, differential superordination -
In this article, the authors introduce two new subclasses of a class m-fold symmetric biunivalent functions in open unit disk. Coefficient bounds for the Taylor-Maclaurin coefficients |am+1| and |a2m+1| are are obtain . Furthermore, we solve ”Fekete-Szeg” ”o” functional problems for functions in FP,m(γ, µ, ϑ) and MP,m(κ, η, ϑ) . Also, several certain special improver results for the associated classes are presented .
Keywords: Analytic functions, Bi-Univalent functions, Fekete-Szeg¨o coefficient, Taylor-Maclaurin series, Univalent functions
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