{"title":"Hankel and Toeplitz determinants for a subclass of analytic functions","authors":"V. MatematychniStudii., No 60, M. Buyankara, M.","doi":"10.30970/ms.60.2.132-137","DOIUrl":null,"url":null,"abstract":"Let the function $f\\left( z \\right) =z+\\sum_{k=2}^{\\infty}a{_{k}}z {^{k}}\\in A$ be locally univalent for $z \\in \\mathbb{D}%:=\\{z \\in \\mathbb{C}:{|}z {|}<1\\}$ and $0\\leq\\alpha<1$.Then, $f$\\textit{\\ }$\\in $ $M(\\alpha )$ if and only if \\begin{equation*}\\Re\\Big( \\left( 1-z ^{2}\\right) \\frac{f(z )}{z }\\Big) >\\alpha,\\quad z \\in \\mathbb{D}.\\end{equation*}%Due to their geometrical characteristics, this class has a significantimpact on the theory of geometric functions. In the article we obtain sharp bounds for the second Hankel determinant \\begin{equation*}\\left\\vert H_{2}\\left( 2\\right) \\left( f\\right) \\right\\vert =\\left\\verta_{2}a_{4}-{a_{3}^{2}}\\right\\vert \\end{equation*}and some Toeplitz determinants \\begin{equation*}\\left\\vert {T}_{3}\\left( 1\\right) \\left( f\\right) \\right\\vert =\\left\\vert 1-2%{a_{2}^{2}}+2{a_{2}^{2}}a_{3}-{a_{3}^{2}}\\right\\vert,\\ \\\\left\\vert {T}_{3}\\left( 2\\right) \\left( f\\right) \\right\\vert =\\left\\vert {%a_{2}^{3}}-2a_{2}{a_{3}^{2}}+2{a_{3}^{2}}a_{4}-a_{2}{a_{4}^{2}}\\right\\vert \\end{equation*}of a subclass of analytic functions $M(\\alpha )$ in the open unit disk $%\\mathbb{D}$.","PeriodicalId":37555,"journal":{"name":"Matematychni Studii","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Matematychni Studii","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.30970/ms.60.2.132-137","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"Mathematics","Score":null,"Total":0}
引用次数: 0
Abstract
Let the function $f\left( z \right) =z+\sum_{k=2}^{\infty}a{_{k}}z {^{k}}\in A$ be locally univalent for $z \in \mathbb{D}%:=\{z \in \mathbb{C}:{|}z {|}<1\}$ and $0\leq\alpha<1$.Then, $f$\textit{\ }$\in $ $M(\alpha )$ if and only if \begin{equation*}\Re\Big( \left( 1-z ^{2}\right) \frac{f(z )}{z }\Big) >\alpha,\quad z \in \mathbb{D}.\end{equation*}%Due to their geometrical characteristics, this class has a significantimpact on the theory of geometric functions. In the article we obtain sharp bounds for the second Hankel determinant \begin{equation*}\left\vert H_{2}\left( 2\right) \left( f\right) \right\vert =\left\verta_{2}a_{4}-{a_{3}^{2}}\right\vert \end{equation*}and some Toeplitz determinants \begin{equation*}\left\vert {T}_{3}\left( 1\right) \left( f\right) \right\vert =\left\vert 1-2%{a_{2}^{2}}+2{a_{2}^{2}}a_{3}-{a_{3}^{2}}\right\vert,\ \\left\vert {T}_{3}\left( 2\right) \left( f\right) \right\vert =\left\vert {%a_{2}^{3}}-2a_{2}{a_{3}^{2}}+2{a_{3}^{2}}a_{4}-a_{2}{a_{4}^{2}}\right\vert \end{equation*}of a subclass of analytic functions $M(\alpha )$ in the open unit disk $%\mathbb{D}$.