{"title":"解析函数的亚高斯随机变量和Wiman不等式","authors":"A. Kuryliak, O. Skaskiv","doi":"10.15330/cmp.15.1.306-314","DOIUrl":null,"url":null,"abstract":"Let $f$ be an analytic function in $\\{z: |z|<R\\}$ of the form $f(z)=\\sum\\limits_{n=0}^{+\\infty}a_n z^n$. In the paper, we consider the Wiman-type inequality for random analytic functions of the form $f(z,\\omega)=\\sum\\limits_{n=0}^{+\\infty}Z_n(\\omega)a_nz^n$, where $(Z_n)$ is a sequence on the Steinhaus probability space of real independent centered sub-Gaussian random variables, i.e. $(\\exists D>0)(\\forall k\\in\\mathbb{N})(\\forall \\lambda\\in\\mathbb{R})\\colon \\mathbf{E}(e^{\\lambda Z_k})\\leq e^{D \\lambda^2}$, and such that $(\\exists\\beta>0)(\\exists n_0\\in\\mathbb{N})\\colon \\inf\\limits_{n\\geq n_0}\\mathbf{E}|Z_n|^{-\\beta}<+\\infty.$ \nIt is proved that for every $\\delta>0$ there exists a set $E(\\delta)\\subset [0,R)$ of finite $h$-logarithmic measure (i.e. $\\int\\nolimits_{E}h(r)d\\ln r<+\\infty$) such that almost surely for all $r\\in(r_0(\\omega),R)\\backslash E$ we have \\[ M_f(r,\\omega):=\\max\\big\\{|f(z,\\omega)|\\colon |z|=r\\big\\}\\leq \\sqrt{h(r)}\\mu_f(r)\\Big(\\ln^3h(r)\\ln\\{h(r)\\mu_f(r)\\}\\Big)^{1/4+\\delta}, \\] where $h(r)$ is any fixed continuous non-decreasing function on $[0;R)$ such that $h(r)\\geq2$ for all $r\\in (0,R)$ and $\\int^R_{r_{0}} h(r) d\\ln r =+\\infty$ for some $r_0\\in(0,R)$.","PeriodicalId":42912,"journal":{"name":"Carpathian Mathematical Publications","volume":null,"pages":null},"PeriodicalIF":1.0000,"publicationDate":"2023-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Sub-Gaussian random variables and Wiman's inequality for analytic functions\",\"authors\":\"A. Kuryliak, O. Skaskiv\",\"doi\":\"10.15330/cmp.15.1.306-314\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Let $f$ be an analytic function in $\\\\{z: |z|<R\\\\}$ of the form $f(z)=\\\\sum\\\\limits_{n=0}^{+\\\\infty}a_n z^n$. In the paper, we consider the Wiman-type inequality for random analytic functions of the form $f(z,\\\\omega)=\\\\sum\\\\limits_{n=0}^{+\\\\infty}Z_n(\\\\omega)a_nz^n$, where $(Z_n)$ is a sequence on the Steinhaus probability space of real independent centered sub-Gaussian random variables, i.e. $(\\\\exists D>0)(\\\\forall k\\\\in\\\\mathbb{N})(\\\\forall \\\\lambda\\\\in\\\\mathbb{R})\\\\colon \\\\mathbf{E}(e^{\\\\lambda Z_k})\\\\leq e^{D \\\\lambda^2}$, and such that $(\\\\exists\\\\beta>0)(\\\\exists n_0\\\\in\\\\mathbb{N})\\\\colon \\\\inf\\\\limits_{n\\\\geq n_0}\\\\mathbf{E}|Z_n|^{-\\\\beta}<+\\\\infty.$ \\nIt is proved that for every $\\\\delta>0$ there exists a set $E(\\\\delta)\\\\subset [0,R)$ of finite $h$-logarithmic measure (i.e. $\\\\int\\\\nolimits_{E}h(r)d\\\\ln r<+\\\\infty$) such that almost surely for all $r\\\\in(r_0(\\\\omega),R)\\\\backslash E$ we have \\\\[ M_f(r,\\\\omega):=\\\\max\\\\big\\\\{|f(z,\\\\omega)|\\\\colon |z|=r\\\\big\\\\}\\\\leq \\\\sqrt{h(r)}\\\\mu_f(r)\\\\Big(\\\\ln^3h(r)\\\\ln\\\\{h(r)\\\\mu_f(r)\\\\}\\\\Big)^{1/4+\\\\delta}, \\\\] where $h(r)$ is any fixed continuous non-decreasing function on $[0;R)$ such that $h(r)\\\\geq2$ for all $r\\\\in (0,R)$ and $\\\\int^R_{r_{0}} h(r) d\\\\ln r =+\\\\infty$ for some $r_0\\\\in(0,R)$.\",\"PeriodicalId\":42912,\"journal\":{\"name\":\"Carpathian Mathematical Publications\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":1.0000,\"publicationDate\":\"2023-06-30\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Carpathian Mathematical Publications\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.15330/cmp.15.1.306-314\",\"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.15.1.306-314","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATHEMATICS","Score":null,"Total":0}
Sub-Gaussian random variables and Wiman's inequality for analytic functions
Let $f$ be an analytic function in $\{z: |z|0)(\forall k\in\mathbb{N})(\forall \lambda\in\mathbb{R})\colon \mathbf{E}(e^{\lambda Z_k})\leq e^{D \lambda^2}$, and such that $(\exists\beta>0)(\exists n_0\in\mathbb{N})\colon \inf\limits_{n\geq n_0}\mathbf{E}|Z_n|^{-\beta}<+\infty.$
It is proved that for every $\delta>0$ there exists a set $E(\delta)\subset [0,R)$ of finite $h$-logarithmic measure (i.e. $\int\nolimits_{E}h(r)d\ln r<+\infty$) such that almost surely for all $r\in(r_0(\omega),R)\backslash E$ we have \[ M_f(r,\omega):=\max\big\{|f(z,\omega)|\colon |z|=r\big\}\leq \sqrt{h(r)}\mu_f(r)\Big(\ln^3h(r)\ln\{h(r)\mu_f(r)\}\Big)^{1/4+\delta}, \] where $h(r)$ is any fixed continuous non-decreasing function on $[0;R)$ such that $h(r)\geq2$ for all $r\in (0,R)$ and $\int^R_{r_{0}} h(r) d\ln r =+\infty$ for some $r_0\in(0,R)$.