univalent functions
در نشریات گروه ریاضی-
This study investigates the geometric characteristics of integral operators connected with the Pascal distribution series. The objective of this article is to establish conditions on the parameters of these operators by utilizing coefficient bounds from class $\mathcal{R}_{\wp,\upsilon}^{\tau}(\gamma)$. Also, the study analyzes the inclusion outcomes of integral operators related to the Pascal distribution series within various subclasses of analytic functions. The findings presented here incorporated previously published results as specific instances.Keywords: Univalent Functions, Starlike Functions, Convex Functions, Spirallike Functions, Pascal Distribution Series
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This paper focuses on a particular type of starlike univalent function, namely $(1-sz)(1+z)$ with $-1/3\leq s\leq 1/3$. This function maps the open unit disk $\mathbb{D}$ onto a Limaçon domain denoted by \[ \left[(u-1)^2+v^2-s^2\right]^2<(1-s)^2\left[\left(u-1-s\right)^2+v^2\right].\] The primary investigation concerns on analytic function families where $zh'/h$ maps the unit disk to a subset of this domain. The paper provides the lower and upper bounds of the real and imaginary parts of these functions and highlights some distinguishing characteristics of these bounds. Furthermore, the study employed subordination theory to derive conclusions and corollaries for functions belonging to the aforementioned class.Keywords: Univalent Functions, Subordination, Starlike Functions, Domain Bounded By Limacon
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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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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 9 -16This paper introduces a new subclass in the open unit disc of analytic functions. It is mainly defined by the modified q-Opoola derivative operator. A coefficient inequality is obtained, and other properties like distortion and closure theorems are derived. Moreover, extreme points of the differential operator are also given. Additionally, Hadamard products (or convolution) of functions respective to the class are also included.Keywords: Univalent functions, Analytic function, Opoola Derivative operator, Hadamard product, q-calculus
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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: 3, Mar 2023, PP 189 -199Let $\mathcal{S}^{\ast}_{L}(\uplambda)$ and $\mathcal{CV}_L(\uplambda)$ be the classes of functions$f$, analytic in the unit disc $\Updelta=\{z\colon|z|<1\}$, with thenormalization $f(0)=f'(0)-1=0$, which satisfies the conditions\begin{equation*}\frac{zf'(z)}{f(z)}\prec \left(1+z\right)^{\uplambda}\quad\text{and}\quad \left(1+\frac{zf''(z)}{f'(z)}\right)\prec \left(1+z\right)^{\uplambda}\qquad \left(0<\uplambda\le 1 \right),\end{equation*}where $\prec$ is the subordination relation, respectively. The classes$\mathcal{S}^{\ast}_{L}(\uplambda)$ and $\mathcal{CV}_L(\uplambda)$ are subfamilies of the known classes of strongly starlike and convex functions of order $\uplambda$. We consider the relations between $\mathcal{S}^{\ast}_{L}(\uplambda)$, $\mathcal{CV}_L(\uplambda)$ and other classes geometrically defined. Also, we obtain the sharp radius of convexity for functions belonging to $\mathcal{S}^{\ast}_{L}(\uplambda)$ class. Furthermore, the norm of pre-Schwarzian derivatives and univalency of functions $f$ which satisfy the condition\begin{equation*}\Re\left\{1+\frac{zf''(z)}{f'(z)}\right\}<1+\frac{\uplambda}{2}\qquad\myp{z \in \Updelta}, \end{equation*}are considered.Keywords: Univalent functions, subordination, strongly starlike functions, Domain bounded by Sinusoidal spiral
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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 1849 -1856In this article, using the concept of q-analogue, we define a new class of analytic functions associated with Chebyshev polynomial of second kind. Then with the help of symmetric q-Chebyshev polynomial, we introduce and estimating first two Maclaurin coefficients for new subclasses of analytic functions. Also as application of the results, we estimate the relevant connection to the famous classical Fekete- Szegö inequality belonging to the class $\tilde{S}_{\Sigma}^{q}(\lambda,\gamma,s).$Keywords: Univalent functions, subordination, q-derivative, q-Chebyshev polynomial, Fekete-Szegö inequality
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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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Let $f$ be function that is analytic in the unit disk $D=\{z:|z|<1\}$, normalized such that $f(0)=f'(0)-1=0$, i.e., of type $f(z)=z+\sum_{n=2}^{\infty} a_n z^n$. If additionally, \[ \left| \left(\frac{z}{f(z)}\right)^2 f'(z) -1\right|<\lambda \quad\quad (z\in D), \]then $f$ belongs to the class $U(\lambda)$, $0<\lambda\le1$. In this paper we prove sharp upper bound of the modulus of the fifth coefficient of $f$ from $U(\lambda)$ in the case when $0.400436\ldots \le\lambda\le1$.Keywords: Univalent functions, Class U($, lambda$), fifth coefficient, sharp estimate
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The aim of this article is to obtain some necessary and sufficient conditions for functions, whose coefficients are probabilities of the Miller-Ross-type Poisson distribution series, to belong to certain subclasses of analytic and univalent functions. Furthermore, we consider an integral operator related to the Miller-Ross type Poisson distribution series.
Keywords: Univalent functions, Miller-Ross Function, Poisson Distribution -
یکی از مباحث بسیار مهم و جذاب در نظریه توابع هندسی، رده های توابع ستاره گون و محدب ما-میندا بر قرص واحد $\mathbb{D}=\left\{z\in \mathbb{C}\colon |z|<1 \right\}$ می باشند که به کمک رابطه تبعیت تعریف شده اند. فرض می کنیم $\mathcal {A}$ رده توابع تحلیلی بر قرص واحد $\mathbb {D}$ در صفحه مختلط $\mathbb {C}$ که با $f (0)=f' (0)-1=0$ نرمالیزه شده و رده های $\ mathcal{ST}_N(s)$ و $ \mathcal{CV}_N (s)$ نمایش خانواده ای از توابع ستاره گون و محدب ما-میندا $f\in \mathcal{A}$ باشند به طوری که برای هر $z\in \mathbb{D}$، کمیت های $zf' (z)/f (z)$ و $1+zf''(z)/f' (z)$ در داخل دامنه کران دار به ناحیه نفرویید \[\left[(u-1)^2+v^2-4s^2\right]^3=108s^4v^2, \quad 0<s\le \frac {\sqrt{2}}{4}\] باشند. در این مقاله، برخی خواص و ویژگی های رده های $\mathcal{ST}_N(s)$ و $\mathcal {CV}_N (s)$ تعریف شده از نوع ما-میندا، مانند ساختار توابع در این رده ها، توابع اکسترمال، قضیه رشد، دگرشکلی و قضیه دوران را مورد مطالعه قرار می دهیم.
کلید واژگان: توابع تک ارز، توابع ستاره گون و محدب، تبعیت، دامنه محدود به نفروئیدOne of the most important and interesting topics in the geometric function theory is the classes of starlike and convex functions of Ma-Minda type on the unit disk D = {z ∈ C: |z| < 1} which are defined by subordination. Let A be the class of functions f, analytic in the unit disc D = {z : |z| < 1} on the complex plane C, with the normalization f(0) = f 0 (0) − 1 = 0, and ST N (s) and CVN (s) be a family of starlike and convex functions f ∈ A so that for each z ∈ D, such that the quantity zf0 (z)/f(z) or 1 + zf00(z)/f0 (z) respectively are lying in the region bounded by the Nephroid (u − 1)2 + v 2 − 4s 2 3 = 108s 4 v 2 , 0 < s ≤ √ 2 4 . In this paper, some properties and characteristics of classes ST N (s) and CVN (s) defined by the Ma-Minda type, like the structure of functions in these classes, we study extreme functions, growth theorem, distoration, and rotation theorem.
Keywords: Univalent functions, Starlike, convex functions, Subordination, domain bounded by Nephroid -
In this paper, we investigate an interesting subclass of univalent functions. Also, we introduce a new subclass of meromorphic bi-univalent functions. We obtain the estimates on the initial Taylor-Maclurin Coefficients for functions in the interesting subclass of meromorphically bi-univalent functions defined on Δ={z∈C: 1<|z|<∞}Δ={z∈C: 1<|z|<∞}.
Keywords: Univalent functions, Meromorphic functions, Meromorphic Bi- univalent functions, Coeffcient estimates, Vertical strip -
In this paper the author used Salagean differential operator to define a certain subclass of spirallike functions and obtain some convolution results and some upper bounds on the coefficients.
Keywords: Univalent functions, Hadamard product, (n, λ)-spirallike functions of order β, Salagean differential operator -
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 -
فرض کنید رده همه توابع تحلیلی و نرمال شده در قرص واحد باشد. برای هر تابع از خانواه ضرایب لگاریتمی به صورت زیر تعریف می شوند:هم چنین، زیررده از را به صورت زیر تعریف می کنیم که در آن " " رابطه تبعیت است. هدف ما در این مقاله تخمین دقیق نامساویها شامل ضرایب لگاریتمی برای توابعی است که به رده تعلق دارند.
کلید واژگان: تابع تک ارز، ستاره واری، تبعیت، ضرایب لگاریتمی، ضرب پیچشیIntroductionLet be the open unit disc in the complex plane and be the class of all functions of which are analytic and normalized in The subclass of consisting of all univalent functions in is denoted by We say that a function is said to be starlike function if and only if for all We denote by the class of all satrlike functions in If and are two of the functions in then we say that is subordinate to written or if there exists a Schwartz function such that for all Furthermore, if the function is univalent in then we have the following equivalence: Also for and their Hadamard product (or convolution) is defined by The logarithmic coefficients of , denoted by , are defined by These coefficients play an important role for various estimates in the theory of univalent functions. For example, consider the Koebe function where It is easy to see that the above function has logarithmic coefficients where and Also for the function we have and the sharp estimates and hold. We remark that the Fekete-Szego theorem is used. For , the problem seems much harder and no significant upper bounds for when appear to be known. Moreover, the problem of finding the sharp upper bound for for is still open for . The sharp upper bounds for modulus of logarithmic coefficients are known for functions in very few subclasses of . For functions in the class it is easy to prove that for and the equality holds for the Koebe function. The celebrated de Brangeschr('39') inequalities (the former Milin conjecture) for univalent functions state that where with the equality if and only if De Branges used this inequality to prove the celebrated Bieberbach conjecture. Moreover, the de Brangeschr('39') inequalities have also been the source of many other interesting inequalities involving logarithmic coefficients of such as Let denote the class of functions and satisfying the following subordination relation where .
Material and methodsIn this paper, first we obtain a subordination relation for the class and by making use of this relation we give two sharp estimates for the logarithmic coefficients of the function
Results and discussionWe obtain two sharp estimates for the logarithmic coefficients of the function
ConclusionThe following conclusions were drawn from this research. Logarithmic coefficients of the function are estimated.
Keywords: Univalent functions, Starlikeness, Subordination, Logarithmic coefficients, Hadamard product -
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 -
International Journal Of Nonlinear Analysis And Applications, Volume:12 Issue: 1, Winter-Spring 2021, PP 2339 -2352
In this paper, we give an upper bound for the fourth Hankel determinant H4(1) for a new class S#C associated with the sine function.
Keywords: analytic functions, univalent functions, fourth-order Hankel determinant, subordination, convex function, sine function
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