{"title":"一类指数系数微分方程的拟星解和拟凸解","authors":"M. Sheremeta","doi":"10.30970/ms.56.1.39-47","DOIUrl":null,"url":null,"abstract":"Dirichlet series $F(s)=e^{s}+\\sum_{k=1}^{\\infty}f_ke^{s\\lambda_k}$ with the exponents $1<\\lambda_k\\uparrow+\\infty$ and the abscissa of absolute convergence $\\sigma_a[F]\\ge 0$ is said to be pseudostarlike of order $\\alpha\\in [0,\\,1)$ and type $\\beta \\in (0,\\,1]$ if$\\left|\\dfrac{F'(s)}{F(s)}-1\\right|<\\beta\\left|\\dfrac{F'(s)}{F(s)}-(2\\alpha-1)\\right|$\\ for all\\ $s\\in \\Pi_0=\\{s\\colon \\,\\text{Re}\\,s<0\\}$. Similarly, the function $F$ is said to be pseudoconvex of order $\\alpha\\in [0,\\,1)$ and type $\\beta \\in (0,\\,1]$ if$\\left|\\dfrac{F''(s)}{F'(s)}-1\\right|<\\beta\\left|\\dfrac{F''(s)}{F'(s)}-(2\\alpha-1)\\right|$\\ for all\\ $s\\in \\Pi_0$. Some conditions are found on the parameters $b_0,\\,b_1,\\,c_0,\\,c_1,\\,\\,c_2$ and the coefficients $a_n$, under which the differential equation $\\dfrac{d^2w}{ds^2}+(b_0e^{s}+b_1)\\dfrac{dw}{ds}+(c_0e^{2s}+c_1e^{s}+c_2)w=\\sum\\limits_{n=1}^{\\infty}a_ne^{ns}$has an entire solution which is pseudostarlike or pseudoconvex of order $\\alpha\\in [0,\\,1)$ and type $\\beta \\in (0,\\,1]$. It is proved that by some conditions for such solution the asymptotic equality holds $\\ln\\,\\max\\{|F(\\sigma+it)|\\colon t\\in {\\mathbb R}\\}=\\dfrac{1+o(1)}{2}\\left(|b_0|+\\sqrt{|b_0|^2+4|c_0|}\\right)$ as $\\sigma \\to+\\infty$.","PeriodicalId":37555,"journal":{"name":"Matematychni Studii","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2021-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":"{\"title\":\"Pseudostarlike and pseudoconvex solutions of a differential equation with exponential coefficients\",\"authors\":\"M. Sheremeta\",\"doi\":\"10.30970/ms.56.1.39-47\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"Dirichlet series $F(s)=e^{s}+\\\\sum_{k=1}^{\\\\infty}f_ke^{s\\\\lambda_k}$ with the exponents $1<\\\\lambda_k\\\\uparrow+\\\\infty$ and the abscissa of absolute convergence $\\\\sigma_a[F]\\\\ge 0$ is said to be pseudostarlike of order $\\\\alpha\\\\in [0,\\\\,1)$ and type $\\\\beta \\\\in (0,\\\\,1]$ if$\\\\left|\\\\dfrac{F'(s)}{F(s)}-1\\\\right|<\\\\beta\\\\left|\\\\dfrac{F'(s)}{F(s)}-(2\\\\alpha-1)\\\\right|$\\\\ for all\\\\ $s\\\\in \\\\Pi_0=\\\\{s\\\\colon \\\\,\\\\text{Re}\\\\,s<0\\\\}$. Similarly, the function $F$ is said to be pseudoconvex of order $\\\\alpha\\\\in [0,\\\\,1)$ and type $\\\\beta \\\\in (0,\\\\,1]$ if$\\\\left|\\\\dfrac{F''(s)}{F'(s)}-1\\\\right|<\\\\beta\\\\left|\\\\dfrac{F''(s)}{F'(s)}-(2\\\\alpha-1)\\\\right|$\\\\ for all\\\\ $s\\\\in \\\\Pi_0$. Some conditions are found on the parameters $b_0,\\\\,b_1,\\\\,c_0,\\\\,c_1,\\\\,\\\\,c_2$ and the coefficients $a_n$, under which the differential equation $\\\\dfrac{d^2w}{ds^2}+(b_0e^{s}+b_1)\\\\dfrac{dw}{ds}+(c_0e^{2s}+c_1e^{s}+c_2)w=\\\\sum\\\\limits_{n=1}^{\\\\infty}a_ne^{ns}$has an entire solution which is pseudostarlike or pseudoconvex of order $\\\\alpha\\\\in [0,\\\\,1)$ and type $\\\\beta \\\\in (0,\\\\,1]$. It is proved that by some conditions for such solution the asymptotic equality holds $\\\\ln\\\\,\\\\max\\\\{|F(\\\\sigma+it)|\\\\colon t\\\\in {\\\\mathbb R}\\\\}=\\\\dfrac{1+o(1)}{2}\\\\left(|b_0|+\\\\sqrt{|b_0|^2+4|c_0|}\\\\right)$ as $\\\\sigma \\\\to+\\\\infty$.\",\"PeriodicalId\":37555,\"journal\":{\"name\":\"Matematychni Studii\",\"volume\":null,\"pages\":null},\"PeriodicalIF\":0.0000,\"publicationDate\":\"2021-10-27\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"\",\"citationCount\":\"1\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Matematychni Studii\",\"FirstCategoryId\":\"1085\",\"ListUrlMain\":\"https://doi.org/10.30970/ms.56.1.39-47\",\"RegionNum\":0,\"RegionCategory\":null,\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q3\",\"JCRName\":\"Mathematics\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Matematychni Studii","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.30970/ms.56.1.39-47","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"Mathematics","Score":null,"Total":0}
Pseudostarlike and pseudoconvex solutions of a differential equation with exponential coefficients
Dirichlet series $F(s)=e^{s}+\sum_{k=1}^{\infty}f_ke^{s\lambda_k}$ with the exponents $1<\lambda_k\uparrow+\infty$ and the abscissa of absolute convergence $\sigma_a[F]\ge 0$ is said to be pseudostarlike of order $\alpha\in [0,\,1)$ and type $\beta \in (0,\,1]$ if$\left|\dfrac{F'(s)}{F(s)}-1\right|<\beta\left|\dfrac{F'(s)}{F(s)}-(2\alpha-1)\right|$\ for all\ $s\in \Pi_0=\{s\colon \,\text{Re}\,s<0\}$. Similarly, the function $F$ is said to be pseudoconvex of order $\alpha\in [0,\,1)$ and type $\beta \in (0,\,1]$ if$\left|\dfrac{F''(s)}{F'(s)}-1\right|<\beta\left|\dfrac{F''(s)}{F'(s)}-(2\alpha-1)\right|$\ for all\ $s\in \Pi_0$. Some conditions are found on the parameters $b_0,\,b_1,\,c_0,\,c_1,\,\,c_2$ and the coefficients $a_n$, under which the differential equation $\dfrac{d^2w}{ds^2}+(b_0e^{s}+b_1)\dfrac{dw}{ds}+(c_0e^{2s}+c_1e^{s}+c_2)w=\sum\limits_{n=1}^{\infty}a_ne^{ns}$has an entire solution which is pseudostarlike or pseudoconvex of order $\alpha\in [0,\,1)$ and type $\beta \in (0,\,1]$. It is proved that by some conditions for such solution the asymptotic equality holds $\ln\,\max\{|F(\sigma+it)|\colon t\in {\mathbb R}\}=\dfrac{1+o(1)}{2}\left(|b_0|+\sqrt{|b_0|^2+4|c_0|}\right)$ as $\sigma \to+\infty$.