<p>In this article, we develop a theory of maximal functions associated with natural approach regions in the setting of spaces of homogeneous type. We construct a natural approach family <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\mathcal {G}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">G</mi> </math></EquationSource> </InlineEquation> and an approach family <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\mathcal {L}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">L</mi> </math></EquationSource> </InlineEquation> such that <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\mathcal {L}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">L</mi> </math></EquationSource> </InlineEquation> satisfies the <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\mathcal {G}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">G</mi> </math></EquationSource> </InlineEquation>-tent condition, and then define maximal operators <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(M_{\mathcal {G}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>M</mi> <mi mathvariant="script">G</mi> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(M_{\mathcal {L},\mathcal {G}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>M</mi> <mrow> <mi mathvariant="script">L</mi> <mo>,</mo> <mi mathvariant="script">G</mi> </mrow> </msub> </math></EquationSource> </InlineEquation>. The <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(L^p\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>L</mi> <mi>p</mi> </msup> </math></EquationSource> </InlineEquation> boundedness, Fefferman-Stein inequalities, and characterizations of weighted weak <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(L^1\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>L</mi> <mn>1</mn> </msup> </math></EquationSource> </InlineEquation> boundedness for both operators <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(M_{\mathcal {G}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>M</mi> <mi mathvariant="script">G</mi> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(M_{\mathcal {L},\mathcal {G}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>M</mi> <mrow> <mi mathvariant="script">L</mi> <mo>,</mo> <mi mathvariant="script">G</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> are established. Furthermore, for an infinite tree <i>T</i> endowed with a very regular property, we construct a space of homogeneous type <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\((bT, \mu _{{T}}, d_e)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mi>b</mi> <mi>T</mi> <mo>,</mo> <msub> <mi>μ</mi> <mi>T</mi> </msub> <mo>,</mo> <msub> <mi>d</mi> <mi>e</mi> </msub> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>, where <i>bT</i> is the boundary of <i>T</i>, <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(\mu _{{T}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>μ</mi> <mi>T</mi> </msub> </math></EquationSource> </InlineEquation> is the hitting distribution and <InlineEquation ID="IEq13"> <EquationSource Format="TEX">\(d_e\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>d</mi> <mi>e</mi> </msub> </math></EquationSource> </InlineEquation> is a metric on <i>T</i>. We define the maximal operator <InlineEquation ID="IEq14"> <EquationSource Format="TEX">\(\mathcal {H}_{\mathcal {L}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="script">H</mi> <mi mathvariant="script">L</mi> </msub> </math></EquationSource> </InlineEquation> on the space <InlineEquation ID="IEq15"> <EquationSource Format="TEX">\((bT, \mu _{{T}})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mi>b</mi> <mi>T</mi> <mo>,</mo> <msub> <mi>μ</mi> <mi>T</mi> </msub> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>, and show the <InlineEquation ID="IEq16"> <EquationSource Format="TEX">\(L^p\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>L</mi> <mi>p</mi> </msup> </math></EquationSource> </InlineEquation> boundedness, Fefferman-Stein inequality, and characterization of weighted weak <InlineEquation ID="IEq17"> <EquationSource Format="TEX">\(L^1\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>L</mi> <mn>1</mn> </msup> </math></EquationSource> </InlineEquation> boundedness for <InlineEquation ID="IEq18"> <EquationSource Format="TEX">\(\mathcal {H}_{\mathcal {L}}.\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi mathvariant="script">H</mi> <mi mathvariant="script">L</mi> </msub> <mo>.</mo> </mrow> </math></EquationSource> </InlineEquation></p>

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Estimates for Hardy-Littlewood Maximal Operators on Approach Regions and Trees

  • Chin-Cheng Lin,
  • Gary Goon Hui Tan

摘要

In this article, we develop a theory of maximal functions associated with natural approach regions in the setting of spaces of homogeneous type. We construct a natural approach family \(\mathcal {G}\) G and an approach family \(\mathcal {L}\) L such that \(\mathcal {L}\) L satisfies the \(\mathcal {G}\) G -tent condition, and then define maximal operators \(M_{\mathcal {G}}\) M G and \(M_{\mathcal {L},\mathcal {G}}\) M L , G . The \(L^p\) L p boundedness, Fefferman-Stein inequalities, and characterizations of weighted weak \(L^1\) L 1 boundedness for both operators \(M_{\mathcal {G}}\) M G and \(M_{\mathcal {L},\mathcal {G}}\) M L , G are established. Furthermore, for an infinite tree T endowed with a very regular property, we construct a space of homogeneous type \((bT, \mu _{{T}}, d_e)\) ( b T , μ T , d e ) , where bT is the boundary of T, \(\mu _{{T}}\) μ T is the hitting distribution and \(d_e\) d e is a metric on T. We define the maximal operator \(\mathcal {H}_{\mathcal {L}}\) H L on the space \((bT, \mu _{{T}})\) ( b T , μ T ) , and show the \(L^p\) L p boundedness, Fefferman-Stein inequality, and characterization of weighted weak \(L^1\) L 1 boundedness for \(\mathcal {H}_{\mathcal {L}}.\) H L .