{"title":"Gabriel's problem for harmonic Hardy spaces","authors":"Suman Das","doi":"arxiv-2408.06623","DOIUrl":null,"url":null,"abstract":"We obtain inequalities of the form $$\\int_C |f(z)|^p |dz| \\leq A(p)\n\\int_{\\mathbb{T}} |f(z)|^p |dz|, \\quad (p>1)$$ where $f$ is harmonic in the\nunit disk $\\mathbb{D}$, $\\mathbb{T}$ is the unit circle, and $C$ is any convex\ncurve in $\\mathbb{D}$. Such inequalities were originally studied for analytic\nfunctions by R. M. Gabriel [Proc. London Math. Soc. (2), 28(2):121-127, 1928].\nWe show that these results, unlike in the case of analytic functions, cannot be\ntrue in general for $0< p \\le 1$. Therefore, we produce an inequality of a\nslightly different type, which deals with the case $0<p<1$. An example is given\nto show that this result is \"best possible\", in the sense that an extension to\n$p=1$ fails. Finally, we consider the special case when $C$ is a circle and\nprove a refined result which, surprisingly, holds for $p=1$ as well.","PeriodicalId":501142,"journal":{"name":"arXiv - MATH - Complex Variables","volume":"17 1","pages":""},"PeriodicalIF":0.0000,"publicationDate":"2024-08-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"arXiv - MATH - Complex Variables","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/arxiv-2408.06623","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 0
Abstract
We obtain inequalities of the form $$\int_C |f(z)|^p |dz| \leq A(p)
\int_{\mathbb{T}} |f(z)|^p |dz|, \quad (p>1)$$ where $f$ is harmonic in the
unit disk $\mathbb{D}$, $\mathbb{T}$ is the unit circle, and $C$ is any convex
curve in $\mathbb{D}$. Such inequalities were originally studied for analytic
functions by R. M. Gabriel [Proc. London Math. Soc. (2), 28(2):121-127, 1928].
We show that these results, unlike in the case of analytic functions, cannot be
true in general for $0< p \le 1$. Therefore, we produce an inequality of a
slightly different type, which deals with the case $0