<p>Let <i>H</i> be a locally compact hypergroup with left Haar measure and let <i>LUC</i>(<i>H</i>) be the collection of left uniformly continuous functions on <i>H</i>. Two new topologies <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2867_Article_IEq1.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\tau _1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>τ</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2867_Article_IEq2.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\tau _2\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>τ</mi> <mn>2</mn> </msub> </math></EquationSource> </InlineEquation> are introduced on <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2867_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="75" /> </InlineMediaObject> <EquationSource Format="TEX">\(LUC(H)^*\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>L</mi> <mi>U</mi> <mi>C</mi> <msup> <mrow> <mo stretchy="false">(</mo> <mi>H</mi> <mo stretchy="false">)</mo> </mrow> <mo>∗</mo> </msup> </mrow> </math></EquationSource> </InlineEquation>. We study these topologies and compare them with each other and with the norm and <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2867_Article_IEq4.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="44" /> </InlineMediaObject> <EquationSource Format="TEX">\(\hbox {weak}^*\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mtext>weak</mtext> <mo>∗</mo> </msup> </math></EquationSource> </InlineEquation>-topologies. For a commutative compact hypergroup <i>H</i>, we deduce that <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2867_Article_IEq1.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\tau _1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>τ</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation>-topology is different from the norm-topology on <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2867_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="75" /> </InlineMediaObject> <EquationSource Format="TEX">\(LUC(H)^*\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>L</mi> <mi>U</mi> <mi>C</mi> <msup> <mrow> <mo stretchy="false">(</mo> <mi>H</mi> <mo stretchy="false">)</mo> </mrow> <mo>∗</mo> </msup> </mrow> </math></EquationSource> </InlineEquation> whenever <i>H</i> is infinite. As another result, we deduce that <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2867_Article_IEq1.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\tau _1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>τ</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> is different from the <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2867_Article_IEq4.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="44" /> </InlineMediaObject> <EquationSource Format="TEX">\(\hbox {weak}^*\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mtext>weak</mtext> <mo>∗</mo> </msup> </math></EquationSource> </InlineEquation>-topology on <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2867_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="75" /> </InlineMediaObject> <EquationSource Format="TEX">\(LUC(H)^*\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>L</mi> <mi>U</mi> <mi>C</mi> <msup> <mrow> <mo stretchy="false">(</mo> <mi>H</mi> <mo stretchy="false">)</mo> </mrow> <mo>∗</mo> </msup> </mrow> </math></EquationSource> </InlineEquation> whenever <i>H</i> is non-compact. The properties of <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2867_Article_IEq1.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\tau _1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>τ</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation> are then studied further and we pay attention to commutant operators on <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2867_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="75" /> </InlineMediaObject> <EquationSource Format="TEX">\(LUC(H)^*\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>L</mi> <mi>U</mi> <mi>C</mi> <msup> <mrow> <mo stretchy="false">(</mo> <mi>H</mi> <mo stretchy="false">)</mo> </mrow> <mo>∗</mo> </msup> </mrow> </math></EquationSource> </InlineEquation>. Finally we give some further results about <InlineEquation ID="IEq12"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2867_Article_IEq1.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="15" /> </InlineMediaObject> <EquationSource Format="TEX">\(\tau _1\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>τ</mi> <mn>1</mn> </msub> </math></EquationSource> </InlineEquation>-continuous operators on <InlineEquation ID="IEq13"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2867_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="75" /> </InlineMediaObject> <EquationSource Format="TEX">\(LUC(H)^*\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>L</mi> <mi>U</mi> <mi>C</mi> <msup> <mrow> <mo stretchy="false">(</mo> <mi>H</mi> <mo stretchy="false">)</mo> </mrow> <mo>∗</mo> </msup> </mrow> </math></EquationSource> </InlineEquation>.</p>

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Convolution Operators and Induced Topology on Hypergroup Algebras

  • Ali Ghaffari,
  • Samane Javadi

摘要

Let H be a locally compact hypergroup with left Haar measure and let LUC(H) be the collection of left uniformly continuous functions on H. Two new topologies \(\tau _1\) τ 1 and \(\tau _2\) τ 2 are introduced on \(LUC(H)^*\) L U C ( H ) . We study these topologies and compare them with each other and with the norm and \(\hbox {weak}^*\) weak -topologies. For a commutative compact hypergroup H, we deduce that \(\tau _1\) τ 1 -topology is different from the norm-topology on \(LUC(H)^*\) L U C ( H ) whenever H is infinite. As another result, we deduce that \(\tau _1\) τ 1 is different from the \(\hbox {weak}^*\) weak -topology on \(LUC(H)^*\) L U C ( H ) whenever H is non-compact. The properties of \(\tau _1\) τ 1 are then studied further and we pay attention to commutant operators on \(LUC(H)^*\) L U C ( H ) . Finally we give some further results about \(\tau _1\) τ 1 -continuous operators on \(LUC(H)^*\) L U C ( H ) .