{"title":"The Legendre-Hardy inequality on bounded domains","authors":"Jaeyoung Byeon, Sangdon Jin","doi":"10.1090/btran/75","DOIUrl":null,"url":null,"abstract":"<p>There have been numerous studies on Hardy’s inequality on a bounded domain, which holds for functions vanishing on the boundary. On the other hand, the classical Legendre differential equation defined in an interval can be regarded as a Neumann version of the Hardy inequality with subcritical weight functions. In this paper we study a Neumann version of the Hardy inequality on a bounded <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"upper C squared\">\n <mml:semantics>\n <mml:msup>\n <mml:mi>C</mml:mi>\n <mml:mn>2</mml:mn>\n </mml:msup>\n <mml:annotation encoding=\"application/x-tex\">C^2</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula>-domain in <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"double-struck upper R Superscript n\">\n <mml:semantics>\n <mml:msup>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mi mathvariant=\"double-struck\">R</mml:mi>\n </mml:mrow>\n <mml:mi>n</mml:mi>\n </mml:msup>\n <mml:annotation encoding=\"application/x-tex\">\\mathbb {R}^n</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula> of the following form <disp-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"integral Underscript normal upper Omega Endscripts d Superscript beta Baseline left-parenthesis x right-parenthesis StartAbsoluteValue nabla u left-parenthesis x right-parenthesis EndAbsoluteValue squared d x greater-than-or-equal-to upper C left-parenthesis alpha comma beta right-parenthesis integral Underscript normal upper Omega Endscripts StartFraction StartAbsoluteValue u left-parenthesis x right-parenthesis EndAbsoluteValue squared Over d Superscript alpha Baseline left-parenthesis x right-parenthesis EndFraction d x with integral Underscript normal upper Omega Endscripts StartFraction u left-parenthesis x right-parenthesis Over d Superscript alpha Baseline left-parenthesis x right-parenthesis EndFraction d x equals 0 comma\">\n <mml:semantics>\n <mml:mrow>\n <mml:msub>\n <mml:mo>∫<!-- ∫ --></mml:mo>\n <mml:mi mathvariant=\"normal\">Ω<!-- Ω --></mml:mi>\n </mml:msub>\n <mml:msup>\n <mml:mi>d</mml:mi>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mi>β<!-- β --></mml:mi>\n </mml:mrow>\n </mml:msup>\n <mml:mo stretchy=\"false\">(</mml:mo>\n <mml:mi>x</mml:mi>\n <mml:mo stretchy=\"false\">)</mml:mo>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mo stretchy=\"false\">|</mml:mo>\n </mml:mrow>\n <mml:mi mathvariant=\"normal\">∇<!-- ∇ --></mml:mi>\n <mml:mi>u</mml:mi>\n <mml:mo stretchy=\"false\">(</mml:mo>\n <mml:mi>x</mml:mi>\n <mml:mo stretchy=\"false\">)</mml:mo>\n <mml:msup>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mo stretchy=\"false\">|</mml:mo>\n </mml:mrow>\n <mml:mn>2</mml:mn>\n </mml:msup>\n <mml:mi>d</mml:mi>\n <mml:mi>x</mml:mi>\n <mml:mo>≥<!-- ≥ --></mml:mo>\n <mml:mi>C</mml:mi>\n <mml:mo stretchy=\"false\">(</mml:mo>\n <mml:mi>α<!-- α --></mml:mi>\n <mml:mo>,</mml:mo>\n <mml:mi>β<!-- β --></mml:mi>\n <mml:mo stretchy=\"false\">)</mml:mo>\n <mml:msub>\n <mml:mo>∫<!-- ∫ --></mml:mo>\n <mml:mi mathvariant=\"normal\">Ω<!-- Ω --></mml:mi>\n </mml:msub>\n <mml:mfrac>\n <mml:mrow>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mo stretchy=\"false\">|</mml:mo>\n </mml:mrow>\n <mml:mi>u</mml:mi>\n <mml:mo stretchy=\"false\">(</mml:mo>\n <mml:mi>x</mml:mi>\n <mml:mo stretchy=\"false\">)</mml:mo>\n <mml:msup>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mo stretchy=\"false\">|</mml:mo>\n </mml:mrow>\n <mml:mn>2</mml:mn>\n </mml:msup>\n </mml:mrow>\n <mml:mrow>\n <mml:msup>\n <mml:mi>d</mml:mi>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mi>α<!-- α --></mml:mi>\n </mml:mrow>\n </mml:msup>\n <mml:mo stretchy=\"false\">(</mml:mo>\n <mml:mi>x</mml:mi>\n <mml:mo stretchy=\"false\">)</mml:mo>\n </mml:mrow>\n </mml:mfrac>\n <mml:mi>d</mml:mi>\n <mml:mi>x</mml:mi>\n <mml:mspace width=\"1em\" />\n <mml:mtext> with </mml:mtext>\n <mml:mspace width=\"1em\" />\n <mml:msub>\n <mml:mo>∫<!-- ∫ --></mml:mo>\n <mml:mi mathvariant=\"normal\">Ω<!-- Ω --></mml:mi>\n </mml:msub>\n <mml:mfrac>\n <mml:mrow>\n <mml:mi>u</mml:mi>\n <mml:mo stretchy=\"false\">(</mml:mo>\n <mml:mi>x</mml:mi>\n <mml:mo stretchy=\"false\">)</mml:mo>\n </mml:mrow>\n <mml:mrow>\n <mml:msup>\n <mml:mi>d</mml:mi>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mi>α<!-- α --></mml:mi>\n </mml:mrow>\n </mml:msup>\n <mml:mo stretchy=\"false\">(</mml:mo>\n <mml:mi>x</mml:mi>\n <mml:mo stretchy=\"false\">)</mml:mo>\n </mml:mrow>\n </mml:mfrac>\n <mml:mi>d</mml:mi>\n <mml:mi>x</mml:mi>\n <mml:mo>=</mml:mo>\n <mml:mn>0</mml:mn>\n <mml:mo>,</mml:mo>\n </mml:mrow>\n <mml:annotation encoding=\"application/x-tex\">\\begin{equation*} \\int _\\Omega d^{\\beta }(x) |\\nabla u(x) |^2 dx \\ge C(\\alpha ,\\beta ) \\int _\\Omega \\frac {|u(x)|^2}{d^{\\alpha }(x)} dx \\quad \\text { with }\\quad \\int _\\Omega \\frac {u(x)}{d^{\\alpha }(x)} dx=0, \\end{equation*}</mml:annotation>\n </mml:semantics>\n</mml:math>\n</disp-formula>\n where <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"d left-parenthesis x right-parenthesis\">\n <mml:semantics>\n <mml:mrow>\n <mml:mi>d</mml:mi>\n <mml:mo stretchy=\"false\">(</mml:mo>\n <mml:mi>x</mml:mi>\n <mml:mo stretchy=\"false\">)</mml:mo>\n </mml:mrow>\n <mml:annotation encoding=\"application/x-tex\">d(x)</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula> is the distance from <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"x element-of normal upper Omega\">\n <mml:semantics>\n <mml:mrow>\n <mml:mi>x</mml:mi>\n <mml:mo>∈<!-- ∈ --></mml:mo>\n <mml:mi mathvariant=\"normal\">Ω<!-- Ω --></mml:mi>\n </mml:mrow>\n <mml:annotation encoding=\"application/x-tex\">x \\in \\Omega</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula> to the boundary <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"partial-differential normal upper Omega\">\n <mml:semantics>\n <mml:mrow>\n <mml:mi mathvariant=\"normal\">∂<!-- ∂ --></mml:mi>\n <mml:mi mathvariant=\"normal\">Ω<!-- Ω --></mml:mi>\n </mml:mrow>\n <mml:annotation encoding=\"application/x-tex\">\\partial \\Omega</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula> and <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"alpha comma beta element-of double-struck upper R\">\n <mml:semantics>\n <mml:mrow>\n <mml:mi>α<!-- α --></mml:mi>\n <mml:mo>,</mml:mo>\n <mml:mi>β<!-- β --></mml:mi>\n <mml:mo>∈<!-- ∈ --></mml:mo>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mi mathvariant=\"double-struck\">R</mml:mi>\n </mml:mrow>\n </mml:mrow>\n <mml:annotation encoding=\"application/x-tex\">\\alpha ,\\beta \\in \\mathbb {R}</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula>. We classify all <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"left-parenthesis alpha comma beta right-parenthesis element-of double-struck upper R squared\">\n <mml:semantics>\n <mml:mrow>\n <mml:mo stretchy=\"false\">(</mml:mo>\n <mml:mi>α<!-- α --></mml:mi>\n <mml:mo>,</mml:mo>\n <mml:mi>β<!-- β --></mml:mi>\n <mml:mo stretchy=\"false\">)</mml:mo>\n <mml:mo>∈<!-- ∈ --></mml:mo>\n <mml:msup>\n <mml:mrow class=\"MJX-TeXAtom-ORD\">\n <mml:mi mathvariant=\"double-struck\">R</mml:mi>\n </mml:mrow>\n <mml:mn>2</mml:mn>\n </mml:msup>\n </mml:mrow>\n <mml:annotation encoding=\"application/x-tex\">(\\alpha ,\\beta ) \\in \\mathbb {R}^2</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula> for which <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"upper C left-parenthesis alpha comma beta right-parenthesis greater-than 0\">\n <mml:semantics>\n <mml:mrow>\n <mml:mi>C</mml:mi>\n <mml:mo stretchy=\"false\">(</mml:mo>\n <mml:mi>α<!-- α --></mml:mi>\n <mml:mo>,</mml:mo>\n <mml:mi>β<!-- β --></mml:mi>\n <mml:mo stretchy=\"false\">)</mml:mo>\n <mml:mo>></mml:mo>\n <mml:mn>0</mml:mn>\n </mml:mrow>\n <mml:annotation encoding=\"application/x-tex\">C(\\alpha ,\\beta ) > 0</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula>. Then, we study whether an optimal constant <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"upper C left-parenthesis alpha comma beta right-parenthesis\">\n <mml:semantics>\n <mml:mrow>\n <mml:mi>C</mml:mi>\n <mml:mo stretchy=\"false\">(</mml:mo>\n <mml:mi>α<!-- α --></mml:mi>\n <mml:mo>,</mml:mo>\n <mml:mi>β<!-- β --></mml:mi>\n <mml:mo stretchy=\"false\">)</mml:mo>\n </mml:mrow>\n <mml:annotation encoding=\"application/x-tex\">C(\\alpha ,\\beta )</mml:annotation>\n </mml:semantics>\n</mml:math>\n</inline-formula> is attained or not. Our study on <inline-formula content-type=\"math/mathml\">\n<mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" alttext=\"upper C left-parenthesis alpha comma beta right-parenthesis\">\n <mml:semantics>\n <mml:mrow>\n <mml:mi>C</mml:mi>\n <mml:mo stretchy=\"false\">(</mml:mo>\n <mml:mi>α<!-- α --></mml","PeriodicalId":377306,"journal":{"name":"Transactions of the American Mathematical Society, Series B","volume":" 8","pages":"0"},"PeriodicalIF":0.0000,"publicationDate":"2022-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"1","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Transactions of the American Mathematical Society, Series B","FirstCategoryId":"1085","ListUrlMain":"https://doi.org/10.1090/btran/75","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"","JCRName":"","Score":null,"Total":0}
引用次数: 1
Abstract
There have been numerous studies on Hardy’s inequality on a bounded domain, which holds for functions vanishing on the boundary. On the other hand, the classical Legendre differential equation defined in an interval can be regarded as a Neumann version of the Hardy inequality with subcritical weight functions. In this paper we study a Neumann version of the Hardy inequality on a bounded C2C^2-domain in Rn\mathbb {R}^n of the following form ∫Ωdβ(x)|∇u(x)|2dx≥C(α,β)∫Ω|u(x)|2dα(x)dx with ∫Ωu(x)dα(x)dx=0,\begin{equation*} \int _\Omega d^{\beta }(x) |\nabla u(x) |^2 dx \ge C(\alpha ,\beta ) \int _\Omega \frac {|u(x)|^2}{d^{\alpha }(x)} dx \quad \text { with }\quad \int _\Omega \frac {u(x)}{d^{\alpha }(x)} dx=0, \end{equation*}
where d(x)d(x) is the distance from x∈Ωx \in \Omega to the boundary ∂Ω\partial \Omega and α,β∈R\alpha ,\beta \in \mathbb {R}. We classify all (α,β)∈R2(\alpha ,\beta ) \in \mathbb {R}^2 for which C(α,β)>0C(\alpha ,\beta ) > 0. Then, we study whether an optimal constant C(α,β)C(\alpha ,\beta ) is attained or not. Our study on C(α