<p>The concept of “standard closed ideals” in the weighted discrete abelian semigroup algebra <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12044_2025_822_Article_IEq1.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="55" /> </InlineMediaObject> <EquationSource Format="TEX">\(l^1(S, \omega )\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>l</mi> <mn>1</mn> </msup> <mrow> <mo stretchy="false">(</mo> <mi>S</mi> <mo>,</mo> <mi>ω</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> is defined in the most general setup. If <i>S</i> is a cancellative, abelian semigroup, then it is shown that the set of all compact elements in <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12044_2025_822_Article_IEq1.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="55" /> </InlineMediaObject> <EquationSource Format="TEX">\(l^1(S, \omega )\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>l</mi> <mn>1</mn> </msup> <mrow> <mo stretchy="false">(</mo> <mi>S</mi> <mo>,</mo> <mi>ω</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> is always a standard closed ideal. A radical weight <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12044_2025_822_Article_IEq3.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="14" /> </InlineMediaObject> <EquationSource Format="TEX">\(\omega \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>ω</mi> </math></EquationSource> </InlineEquation> on <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12044_2025_822_Article_IEq4.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="22" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathbb {Z}}_+\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="double-struck">Z</mi> <mo>+</mo> </msub> </math></EquationSource> </InlineEquation> is constructed such that <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12044_2025_822_Article_IEq5.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="65" /> </InlineMediaObject> <EquationSource Format="TEX">\(l^1({\mathbb {Z}}_+, \omega )\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>l</mi> <mn>1</mn> </msup> <mrow> <mo stretchy="false">(</mo> <msub> <mi mathvariant="double-struck">Z</mi> <mo>+</mo> </msub> <mo>,</mo> <mi>ω</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> does not have any non-zero compact element. The weighted discrete analogues of some results on the compact elements in <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="12044_2025_822_Article_IEq6.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="70" /> </InlineMediaObject> <EquationSource Format="TEX">\(L^1({\mathbb {R}}_+, \omega )\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>L</mi> <mn>1</mn> </msup> <mrow> <mo stretchy="false">(</mo> <msub> <mi mathvariant="double-struck">R</mi> <mo>+</mo> </msub> <mo>,</mo> <mi>ω</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> given in&#xa0;[<CitationRef CitationID="CR2">2</CitationRef>] are proved. Various counter examples are exhibited. Moreover, this article will set the record right by correcting some results of&#xa0;[<CitationRef CitationID="CR6">6</CitationRef>].</p>

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Compact elements in weighted discrete abelian semigroup algebras

  • K R Baleviya,
  • H V Dedania

摘要

The concept of “standard closed ideals” in the weighted discrete abelian semigroup algebra \(l^1(S, \omega )\) l 1 ( S , ω ) is defined in the most general setup. If S is a cancellative, abelian semigroup, then it is shown that the set of all compact elements in \(l^1(S, \omega )\) l 1 ( S , ω ) is always a standard closed ideal. A radical weight \(\omega \) ω on \({\mathbb {Z}}_+\) Z + is constructed such that \(l^1({\mathbb {Z}}_+, \omega )\) l 1 ( Z + , ω ) does not have any non-zero compact element. The weighted discrete analogues of some results on the compact elements in \(L^1({\mathbb {R}}_+, \omega )\) L 1 ( R + , ω ) given in [2] are proved. Various counter examples are exhibited. Moreover, this article will set the record right by correcting some results of [6].