<p>Let <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11117_2025_1121_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="62" /> </InlineMediaObject> <EquationSource Format="TEX">\((\Omega ,\Sigma ,\mu )\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="normal">Ω</mi> <mo>,</mo> <mi mathvariant="normal">Σ</mi> <mo>,</mo> <mi>μ</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> be a finite measure space and <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11117_2025_1121_Article_IEq2.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="73" /> </InlineMediaObject> <EquationSource Format="TEX">\((X,\Vert \cdot \Vert _x)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mi>X</mi> <mo>,</mo> <mo stretchy="false">‖</mo> <mo>·</mo> <msub> <mo stretchy="false">‖</mo> <mi>x</mi> </msub> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11117_2025_1121_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="72" /> </InlineMediaObject> <EquationSource Format="TEX">\((Y,\Vert \cdot \Vert _Y)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mi>Y</mi> <mo>,</mo> <mo stretchy="false">‖</mo> <mo>·</mo> <msub> <mo stretchy="false">‖</mo> <mi>Y</mi> </msub> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> be Banach spaces. A linear operator <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11117_2025_1121_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="136" /> </InlineMediaObject> <EquationSource Format="TEX">\(T:L^\infty (\mu ,X)\rightarrow Y\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>T</mi> <mo>:</mo> <msup> <mi>L</mi> <mi>∞</mi> </msup> <mrow> <mo stretchy="false">(</mo> <mi>μ</mi> <mo>,</mo> <mi>X</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">→</mo> <mi>Y</mi> </mrow> </math></EquationSource> </InlineEquation> is said to be dominated if there exists a positive function <i>v</i> in <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11117_2025_1121_Article_IEq5.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="42" /> </InlineMediaObject> <EquationSource Format="TEX">\(L^1(\mu )\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>L</mi> <mn>1</mn> </msup> <mrow> <mo stretchy="false">(</mo> <mi>μ</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> so that <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11117_2025_1121_Article_IEq6.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="225" /> </InlineMediaObject> <EquationSource Format="TEX">\(\Vert T(f)\Vert _Y\le \int _\Omega \Vert f(\omega )\Vert _X v(\omega )\,d\mu \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mrow> <mo stretchy="false">‖</mo> <mi>T</mi> <mrow> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">‖</mo> </mrow> <mi>Y</mi> </msub> <mo>≤</mo> <msub> <mo>∫</mo> <mi mathvariant="normal">Ω</mi> </msub> <msub> <mrow> <mo stretchy="false">‖</mo> <mi>f</mi> <mrow> <mo stretchy="false">(</mo> <mi>ω</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">‖</mo> </mrow> <mi>X</mi> </msub> <mi>v</mi> <mrow> <mo stretchy="false">(</mo> <mi>ω</mi> <mo stretchy="false">)</mo> </mrow> <mspace width="0.166667em" /> <mi>d</mi> <mi>μ</mi> </mrow> </math></EquationSource> </InlineEquation> for every <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11117_2025_1121_Article_IEq7.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="103" /> </InlineMediaObject> <EquationSource Format="TEX">\(f\in L^\infty (\mu ,X)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mo>∈</mo> <msup> <mi>L</mi> <mi>∞</mi> </msup> <mrow> <mo stretchy="false">(</mo> <mi>μ</mi> <mo>,</mo> <mi>X</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>. It is shown that a bounded linear operator <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11117_2025_1121_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="136" /> </InlineMediaObject> <EquationSource Format="TEX">\(T:L^\infty (\mu ,X)\rightarrow Y\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>T</mi> <mo>:</mo> <msup> <mi>L</mi> <mi>∞</mi> </msup> <mrow> <mo stretchy="false">(</mo> <mi>μ</mi> <mo>,</mo> <mi>X</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">→</mo> <mi>Y</mi> </mrow> </math></EquationSource> </InlineEquation> is dominated if and only if its representing measure <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11117_2025_1121_Article_IEq9.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="25" /> </InlineMediaObject> <EquationSource Format="TEX">\(m_T\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>m</mi> <mi>T</mi> </msub> </math></EquationSource> </InlineEquation> is <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11117_2025_1121_Article_IEq10.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mu \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>μ</mi> </math></EquationSource> </InlineEquation>-absolutely continuous and has the finite variation <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11117_2025_1121_Article_IEq11.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="39" /> </InlineMediaObject> <EquationSource Format="TEX">\(|m_T|\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mrow> <mo stretchy="false">|</mo> </mrow> <msub> <mi>m</mi> <mi>T</mi> </msub> <mrow> <mo stretchy="false">|</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>. Moreover, the relationship between dominated operators <InlineEquation ID="IEq12"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11117_2025_1121_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="136" /> </InlineMediaObject> <EquationSource Format="TEX">\(T:L^\infty (\mu ,X)\rightarrow Y\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>T</mi> <mo>:</mo> <msup> <mi>L</mi> <mi>∞</mi> </msup> <mrow> <mo stretchy="false">(</mo> <mi>μ</mi> <mo>,</mo> <mi>X</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">→</mo> <mi>Y</mi> </mrow> </math></EquationSource> </InlineEquation> and their associated operators <InlineEquation ID="IEq13"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11117_2025_1121_Article_IEq13.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="171" /> </InlineMediaObject> <EquationSource Format="TEX">\(T^\#:L^\infty (\mu )\rightarrow \mathcal {L}(X,Y)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>T</mi> <mo>#</mo> </msup> <mo>:</mo> <msup> <mi>L</mi> <mi>∞</mi> </msup> <mrow> <mo stretchy="false">(</mo> <mi>μ</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">→</mo> <mi mathvariant="script">L</mi> <mrow> <mo stretchy="false">(</mo> <mi>X</mi> <mo>,</mo> <mi>Y</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> is established.</p>

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Dominated operators on the space of vector-valued essentially bounded measurable functions

  • Marian Nowak

摘要

Let \((\Omega ,\Sigma ,\mu )\) ( Ω , Σ , μ ) be a finite measure space and \((X,\Vert \cdot \Vert _x)\) ( X , · x ) and \((Y,\Vert \cdot \Vert _Y)\) ( Y , · Y ) be Banach spaces. A linear operator \(T:L^\infty (\mu ,X)\rightarrow Y\) T : L ( μ , X ) Y is said to be dominated if there exists a positive function v in \(L^1(\mu )\) L 1 ( μ ) so that \(\Vert T(f)\Vert _Y\le \int _\Omega \Vert f(\omega )\Vert _X v(\omega )\,d\mu \) T ( f ) Y Ω f ( ω ) X v ( ω ) d μ for every \(f\in L^\infty (\mu ,X)\) f L ( μ , X ) . It is shown that a bounded linear operator \(T:L^\infty (\mu ,X)\rightarrow Y\) T : L ( μ , X ) Y is dominated if and only if its representing measure \(m_T\) m T is \(\mu \) μ -absolutely continuous and has the finite variation \(|m_T|\) | m T | . Moreover, the relationship between dominated operators \(T:L^\infty (\mu ,X)\rightarrow Y\) T : L ( μ , X ) Y and their associated operators \(T^\#:L^\infty (\mu )\rightarrow \mathcal {L}(X,Y)\) T # : L ( μ ) L ( X , Y ) is established.