<p>Let <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2965_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="47" /> </InlineMediaObject> <EquationSource Format="TEX">\((A,\mathfrak {m} )\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mi>A</mi> <mo>,</mo> <mi mathvariant="fraktur">m</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> be a complete Cohen–Macaulay local ring. Assume <i>A</i> is not Gorenstein. We say <i>A</i> is a Teter ring if there exists a complete Gorenstein ring <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2965_Article_IEq2.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="44" /> </InlineMediaObject> <EquationSource Format="TEX">\((B,\mathfrak {n} )\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mi>B</mi> <mo>,</mo> <mi mathvariant="fraktur">n</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> with <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2965_Article_IEq3.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="111" /> </InlineMediaObject> <EquationSource Format="TEX">\(\dim B = \dim A\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>dim</mo> <mi>B</mi> <mo>=</mo> <mo>dim</mo> <mi>A</mi> </mrow> </math></EquationSource> </InlineEquation> and a surjective map <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2965_Article_IEq4.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="58" /> </InlineMediaObject> <EquationSource Format="TEX">\(B \rightarrow A\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>B</mi> <mo stretchy="false">→</mo> <mi>A</mi> </mrow> </math></EquationSource> </InlineEquation> with <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2965_Article_IEq5.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="119" /> </InlineMediaObject> <EquationSource Format="TEX">\(e(B) - e(A) = 1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>e</mi> <mo stretchy="false">(</mo> <mi>B</mi> <mo stretchy="false">)</mo> <mo>-</mo> <mi>e</mi> <mo stretchy="false">(</mo> <mi>A</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation> (here <i>e</i>(<i>A</i>) denotes multiplicity of <i>A</i>). We give an intrinsic characterization of Teter rings which are domains. We say a Teter ring is a strongly Teter ring if <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2965_Article_IEq6.gif" Format="GIF" Height="23" Rendition="HTML" Resolution="72" Type="Linedraw" Width="154" /> </InlineMediaObject> <EquationSource Format="TEX">\(G(B) = \bigoplus _{i \ge 0}\mathfrak {n} ^i/\mathfrak {n} ^{i+1}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>G</mi> <mrow> <mo stretchy="false">(</mo> <mi>B</mi> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <msub> <mo>⨁</mo> <mrow> <mi>i</mi> <mo>≥</mo> <mn>0</mn> </mrow> </msub> <msup> <mrow> <mi mathvariant="fraktur">n</mi> </mrow> <mi>i</mi> </msup> <mo stretchy="false">/</mo> <msup> <mrow> <mi mathvariant="fraktur">n</mi> </mrow> <mrow> <mi>i</mi> <mo>+</mo> <mn>1</mn> </mrow> </msup> </mrow> </math></EquationSource> </InlineEquation> is also a Gorenstein ring. We give an intrinsic characterizations of strongly Teter rings which are domains. If <i>k</i> is algebraically closed field of characteristic zero and <i>R</i> is a standard graded Cohen–Macaulay <i>k</i>-algebra of finite representation type (and not Gorenstein), then we show that <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2965_Article_IEq7.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="27" /> </InlineMediaObject> <EquationSource Format="TEX">\(\widehat{R_\mathfrak {M} }\)</EquationSource> <EquationSource Format="MATHML"><math> <mover accent="true"> <msub> <mi>R</mi> <mi mathvariant="fraktur">M</mi> </msub> <mo stretchy="true">^</mo> </mover> </math></EquationSource> </InlineEquation> is a Teter ring (here <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="9_2025_2965_Article_IEq8.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="20" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathfrak {M} \)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="fraktur">M</mi> </math></EquationSource> </InlineEquation> is the maximal homogeneous ideal of <i>R</i>).</p>

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Higher Dimensional Teter Rings

  • Tony J. Puthenpurakal

摘要

Let \((A,\mathfrak {m} )\) ( A , m ) be a complete Cohen–Macaulay local ring. Assume A is not Gorenstein. We say A is a Teter ring if there exists a complete Gorenstein ring \((B,\mathfrak {n} )\) ( B , n ) with \(\dim B = \dim A\) dim B = dim A and a surjective map \(B \rightarrow A\) B A with \(e(B) - e(A) = 1\) e ( B ) - e ( A ) = 1 (here e(A) denotes multiplicity of A). We give an intrinsic characterization of Teter rings which are domains. We say a Teter ring is a strongly Teter ring if \(G(B) = \bigoplus _{i \ge 0}\mathfrak {n} ^i/\mathfrak {n} ^{i+1}\) G ( B ) = i 0 n i / n i + 1 is also a Gorenstein ring. We give an intrinsic characterizations of strongly Teter rings which are domains. If k is algebraically closed field of characteristic zero and R is a standard graded Cohen–Macaulay k-algebra of finite representation type (and not Gorenstein), then we show that \(\widehat{R_\mathfrak {M} }\) R M ^ is a Teter ring (here \(\mathfrak {M} \) M is the maximal homogeneous ideal of R).