{"title":"单位球内整体函数和解析函数的组成","authors":"Andriy Ivanovych Bandura, O. Skaskiv, I. Tymkiv","doi":"10.15330/cmp.14.1.95-104","DOIUrl":null,"url":null,"abstract":"In this paper, we investigate a composition of entire function of several complex variables and analytic function in the unit ball. We modified early known results with conditions providing equivalence of boundedness of $L$-index in a direction for such a composition and boundedness of $l$-index of initial function of one variable, where the continuous function $L:\\mathbb{B}^n\\to \\mathbb{R}_+$ is constructed by the continuous function $l: \\mathbb{C}^m\\to \\mathbb{R}_+.$ Taking into account new ideas from recent results on composition of entire functions, we remove a condition that a directional derivative of the inner function $\\Phi$ in the composition does not equal to zero. Instead of the condition we construct a greater function $L(z)$ for which $F(z)=f(\\underbrace{\\Phi(z),\\ldots,\\Phi(z)}_{m\\text{ times}})$ has bounded $L$-index in a direction, where $f\\colon \\mathbb{C}^m\\to \\mathbb{C}$ is an entire function of bounded $l$-index in the direction $(1,\\ldots,1)$, $\\Phi\\colon \\mathbb{B}^n\\to \\mathbb{C}$ is an analytic function in the unit ball. \nWe weaken the condition $|\\partial_{\\mathbf{b}}^k\\Phi(z)|\\le K|\\partial_{\\mathbf{b}}\\Phi(z)|^k$ for all $z\\in\\mathbb{B}^n$, where $K\\geq 1$ is a constant, $\\mathbf{b}\\in\\mathbb{C}^n\\setminus\\{0\\}$ is a given direction and $${\\partial_{\\mathbf{b}} F(z)}:=\\sum\\limits_{j=1}^{n}\\!\\frac{\\partial F(z)}{\\partial z_{j}}{b_{j}}, \\ \\partial_{\\mathbf{b}}^k F(z):=\\partial_{\\mathbf{b}}\\big(\\partial_{\\mathbf{b}}^{k-1} F(z)\\big).$$ It is replaced by the condition $|\\partial_{\\mathbf{b}}^k\\Phi(z)|\\le K(l(\\Phi(z)))^{1/(N_{\\mathbf{1}}(f,l)+1)}|\\partial_{\\mathbf{b}}\\Phi(z)|^k$, where $N_{\\mathbf{1}}(f,l)$ is the $l$-index of the function $f$ in the direction $\\mathbf{1}=(1,\\ldots,1).$ The described result is an improvement of previous one. It is also a new result for the one-dimensional case $n=1,$ $m=1$, i.e. for an analytic function $\\Phi$ in the unit disc and for an entire function $f: \\mathbb{C}\\to\\mathbb{C}$ of bounded $l$-index.","PeriodicalId":42912,"journal":{"name":"Carpathian Mathematical Publications","volume":null,"pages":null},"PeriodicalIF":1.0000,"publicationDate":"2022-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":"{\"title\":\"Composition of entire and analytic functions in the unit ball\",\"authors\":\"Andriy Ivanovych Bandura, O. Skaskiv, I. Tymkiv\",\"doi\":\"10.15330/cmp.14.1.95-104\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"In this paper, we investigate a composition of entire function of several complex variables and analytic function in the unit ball. We modified early known results with conditions providing equivalence of boundedness of $L$-index in a direction for such a composition and boundedness of $l$-index of initial function of one variable, where the continuous function $L:\\\\mathbb{B}^n\\\\to \\\\mathbb{R}_+$ is constructed by the continuous function $l: \\\\mathbb{C}^m\\\\to \\\\mathbb{R}_+.$ Taking into account new ideas from recent results on composition of entire functions, we remove a condition that a directional derivative of the inner function $\\\\Phi$ in the composition does not equal to zero. Instead of the condition we construct a greater function $L(z)$ for which $F(z)=f(\\\\underbrace{\\\\Phi(z),\\\\ldots,\\\\Phi(z)}_{m\\\\text{ times}})$ has bounded $L$-index in a direction, where $f\\\\colon \\\\mathbb{C}^m\\\\to \\\\mathbb{C}$ is an entire function of bounded $l$-index in the direction $(1,\\\\ldots,1)$, $\\\\Phi\\\\colon \\\\mathbb{B}^n\\\\to \\\\mathbb{C}$ is an analytic function in the unit ball. \\nWe weaken the condition $|\\\\partial_{\\\\mathbf{b}}^k\\\\Phi(z)|\\\\le K|\\\\partial_{\\\\mathbf{b}}\\\\Phi(z)|^k$ for all $z\\\\in\\\\mathbb{B}^n$, where $K\\\\geq 1$ is a constant, $\\\\mathbf{b}\\\\in\\\\mathbb{C}^n\\\\setminus\\\\{0\\\\}$ is a given direction and $${\\\\partial_{\\\\mathbf{b}} F(z)}:=\\\\sum\\\\limits_{j=1}^{n}\\\\!\\\\frac{\\\\partial F(z)}{\\\\partial z_{j}}{b_{j}}, \\\\ \\\\partial_{\\\\mathbf{b}}^k F(z):=\\\\partial_{\\\\mathbf{b}}\\\\big(\\\\partial_{\\\\mathbf{b}}^{k-1} F(z)\\\\big).$$ It is replaced by the condition $|\\\\partial_{\\\\mathbf{b}}^k\\\\Phi(z)|\\\\le K(l(\\\\Phi(z)))^{1/(N_{\\\\mathbf{1}}(f,l)+1)}|\\\\partial_{\\\\mathbf{b}}\\\\Phi(z)|^k$, where $N_{\\\\mathbf{1}}(f,l)$ is the $l$-index of the function $f$ in the direction $\\\\mathbf{1}=(1,\\\\ldots,1).$ The described result is an improvement of previous one. It is also a new result for the one-dimensional case $n=1,$ $m=1$, i.e. for an analytic function $\\\\Phi$ in the unit disc and for an entire function $f: \\\\mathbb{C}\\\\to\\\\mathbb{C}$ of bounded $l$-index.\",\"PeriodicalId\":42912,\"journal\":{\"name\":\"Carpathian Mathematical Publications\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":1.0000,\"publicationDate\":\"2022-06-09\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"1\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Carpathian Mathematical Publications\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.15330/cmp.14.1.95-104\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q1\",\"JCRName\":\"MATHEMATICS\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Carpathian Mathematical Publications","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.15330/cmp.14.1.95-104","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATHEMATICS","Score":null,"Total":0}
Composition of entire and analytic functions in the unit ball
In this paper, we investigate a composition of entire function of several complex variables and analytic function in the unit ball. We modified early known results with conditions providing equivalence of boundedness of $L$-index in a direction for such a composition and boundedness of $l$-index of initial function of one variable, where the continuous function $L:\mathbb{B}^n\to \mathbb{R}_+$ is constructed by the continuous function $l: \mathbb{C}^m\to \mathbb{R}_+.$ Taking into account new ideas from recent results on composition of entire functions, we remove a condition that a directional derivative of the inner function $\Phi$ in the composition does not equal to zero. Instead of the condition we construct a greater function $L(z)$ for which $F(z)=f(\underbrace{\Phi(z),\ldots,\Phi(z)}_{m\text{ times}})$ has bounded $L$-index in a direction, where $f\colon \mathbb{C}^m\to \mathbb{C}$ is an entire function of bounded $l$-index in the direction $(1,\ldots,1)$, $\Phi\colon \mathbb{B}^n\to \mathbb{C}$ is an analytic function in the unit ball.
We weaken the condition $|\partial_{\mathbf{b}}^k\Phi(z)|\le K|\partial_{\mathbf{b}}\Phi(z)|^k$ for all $z\in\mathbb{B}^n$, where $K\geq 1$ is a constant, $\mathbf{b}\in\mathbb{C}^n\setminus\{0\}$ is a given direction and $${\partial_{\mathbf{b}} F(z)}:=\sum\limits_{j=1}^{n}\!\frac{\partial F(z)}{\partial z_{j}}{b_{j}}, \ \partial_{\mathbf{b}}^k F(z):=\partial_{\mathbf{b}}\big(\partial_{\mathbf{b}}^{k-1} F(z)\big).$$ It is replaced by the condition $|\partial_{\mathbf{b}}^k\Phi(z)|\le K(l(\Phi(z)))^{1/(N_{\mathbf{1}}(f,l)+1)}|\partial_{\mathbf{b}}\Phi(z)|^k$, where $N_{\mathbf{1}}(f,l)$ is the $l$-index of the function $f$ in the direction $\mathbf{1}=(1,\ldots,1).$ The described result is an improvement of previous one. It is also a new result for the one-dimensional case $n=1,$ $m=1$, i.e. for an analytic function $\Phi$ in the unit disc and for an entire function $f: \mathbb{C}\to\mathbb{C}$ of bounded $l$-index.