关于对称点的函数的对数系数的尖锐界限问题

Q3 Mathematics Matematychni Studii Pub Date : 2023-03-28 DOI:10.30970/ms.59.1.68-75
N. H. Mohammed
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引用次数: 3

摘要

在一元函数理论中,对数系数对不同的估计起着重要的作用。由于近年来对数系数研究的重要性,这些系数的第二次汉克尔行列式的锐界问题,即 $H_{2,1}(F_f/2)$ 得到了关注。我们记得,如果 $f$ 和 $F$ 有两个解析函数吗 $\mathbb{D}$,函数 $f$ 从属于 $F$,写的 $f(z)\prec F(z)$,如果存在解析函数 $\omega$ 在 $\mathbb{D}$ 有 $\omega(0)=0$ 和 $|\omega(z)|<1$,这样 $f(z)=F\left(\omega(z)\right)$ 对所有人 $z\in\mathbb{D}$。众所周知, $F$ 是一元的 $\mathbb{D}$那么, $f(z)\prec F(z)$ 当且仅当 $f(0)=F(0)$ 和 $f(\mathbb{D})\subset F(\mathbb{D})$a函数 $f\in\mathcal{A}$ 对于对称点是星形的吗 $\mathbb{D}$ 如果每 $r$ 接近于 $1,$ $r < 1$ 每一个 $z_0$ on $|z| = r$ 的角速度 $f(z)$关于 $f(-z_0)$ 是正的 $z = z_0$ as $z$ 穿过圆 $|z| = r$ 朝积极的方向。在目前的研究中,我们得到了对数系数的第二汉克尔行列式的锐界 $\mathcal{S}_s^*(\psi)$ 和 $\mathcal{C}_s(\psi)$ 我们在哪里定义了从属和从属的概念 $\psi$ 被认为是单价的 $\mathbb{D}$ 实部为正 $\mathbb{D}$ 并且满足条件 $\psi(0)=1$。请注意 $f\in \mathcal{S}_s^*(\psi)$ 如果\[\dfrac{2zf^\prime(z)}{f(z)-f(-z)}\prec\psi(z),\quad z\in\mathbb{D}\]和 $f\in \mathcal{C}_s(\psi)$ 如果\[\dfrac{2(zf^\prime(z))^\prime}{f^\prime(z)+f^\prime(-z)}\prec\psi(z),\quad z\in\mathbb{D}.\]值得一提的是,本文给出的边界扩展和发展了文献中最近的一些相关结果。此外,这些定理所给出的结果可用于确定的上界 $\left\vert H_{2,1}(F_f/2)\right\vert$ 其他受欢迎的家庭。
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Sharp bounds of logarithmic coefficient problems for functions with respect to symmetric points
The logarithmic coefficients play an important role for different estimates in the theory of univalent functions.Due to the significance of the recent studies about the logarithmic coefficients, the problem of obtaining the sharp bounds for the second Hankel determinant of these coefficients, that is $H_{2,1}(F_f/2)$ was paid attention. We recall that if $f$ and $F$ are two analytic functions in $\mathbb{D}$, the function $f$ is subordinate to $F$, written $f(z)\prec F(z)$, if there exists an analytic function $\omega$ in $\mathbb{D}$ with $\omega(0)=0$ and $|\omega(z)|<1$, such that $f(z)=F\left(\omega(z)\right)$ for all $z\in\mathbb{D}$. It is well-known that if $F$ is univalent in $\mathbb{D}$, then $f(z)\prec F(z)$ if and only if $f(0)=F(0)$ and $f(\mathbb{D})\subset F(\mathbb{D})$.A function $f\in\mathcal{A}$ is starlike with respect to symmetric points in $\mathbb{D}$ iffor every $r$ close to $1,$ $r < 1$ and every $z_0$ on $|z| = r$ the angular velocity of $f(z)$about $f(-z_0)$ is positive at $z = z_0$ as $z$ traverses the circle $|z| = r$ in the positivedirection. In the current study, we obtain the sharp bounds of the second Hankel determinant of the logarithmic coefficients for families $\mathcal{S}_s^*(\psi)$ and $\mathcal{C}_s(\psi)$ where were defined by the concept subordination and $\psi$ is considered univalent in $\mathbb{D}$ with positive real part in $\mathbb{D}$ and satisfies the condition $\psi(0)=1$. Note that $f\in \mathcal{S}_s^*(\psi)$ if\[\dfrac{2zf^\prime(z)}{f(z)-f(-z)}\prec\psi(z),\quad z\in\mathbb{D}\]and $f\in \mathcal{C}_s(\psi)$ if\[\dfrac{2(zf^\prime(z))^\prime}{f^\prime(z)+f^\prime(-z)}\prec\psi(z),\quad z\in\mathbb{D}.\]It is worthwhile mentioning that the given bounds in this paper extend and develop some related recent results in the literature. In addition, the results given in these theorems can be used for determining the upper bound of $\left\vert H_{2,1}(F_f/2)\right\vert$ for other popular families.
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来源期刊
Matematychni Studii
Matematychni Studii Mathematics-Mathematics (all)
CiteScore
1.00
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0.00%
发文量
38
期刊介绍: Journal is devoted to research in all fields of mathematics.
期刊最新文献
On the h-measure of an exceptional set in Fenton-type theorem for Taylor-Dirichlet series Almost periodic distributions and crystalline measures Reflectionless Schrodinger operators and Marchenko parametrization Existence of basic solutions of first order linear homogeneous set-valued differential equations Real univariate polynomials with given signs of coefficients and simple real roots
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