<p>Let <i>X</i> be a matrix of indeterminates, <i>t</i> an integer, and <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13348_2025_494_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="45" /> </InlineMediaObject> <EquationSource Format="TEX">\(P_t(X)\)</EquationSource> </InlineEquation> define the ideal generated by the permanents of all <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13348_2025_494_Article_IEq2.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="38" /> </InlineMediaObject> <EquationSource Format="TEX">\(t\times t\)</EquationSource> </InlineEquation> submatrix of <i>X</i>. <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13348_2025_494_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="45" /> </InlineMediaObject> <EquationSource Format="TEX">\(P_t(X)\)</EquationSource> </InlineEquation> is called a permanental ideal. In this article, we study the algebras <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13348_2025_494_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="87" /> </InlineMediaObject> <EquationSource Format="TEX">\(\Bbbk [X]/P_t(X)\)</EquationSource> </InlineEquation> where <i>X</i> is a generic, symmetric, or a Hankel matrix of indeterminates. When <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13348_2025_494_Article_IEq5.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="74" /> </InlineMediaObject> <EquationSource Format="TEX">\({{\,\textrm{char}\,}}\Bbbk = 2\)</EquationSource> </InlineEquation>, <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13348_2025_494_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="45" /> </InlineMediaObject> <EquationSource Format="TEX">\(P_t(X)\)</EquationSource> </InlineEquation> is also known as a determinantal ideal, a popular class in commutative algebra and algebraic geometry, and thus many properties of <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13348_2025_494_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="45" /> </InlineMediaObject> <EquationSource Format="TEX">\(P_t(X)\)</EquationSource> </InlineEquation> are known in this case. We prove that, if <i>X</i> is an <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13348_2025_494_Article_IEq8.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="45" /> </InlineMediaObject> <EquationSource Format="TEX">\(n\times n\)</EquationSource> </InlineEquation> matrix and <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13348_2025_494_Article_IEq9.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="75" /> </InlineMediaObject> <EquationSource Format="TEX">\({{\,\textrm{char}\,}}\Bbbk &gt;2\)</EquationSource> </InlineEquation>, the algebra <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13348_2025_494_Article_IEq10.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="90" /> </InlineMediaObject> <EquationSource Format="TEX">\(\Bbbk [X]/P_n(X)\)</EquationSource> </InlineEquation> is <i>F</i>-regular, just like when <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13348_2025_494_Article_IEq5.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="74" /> </InlineMediaObject> <EquationSource Format="TEX">\({{\,\textrm{char}\,}}\Bbbk = 2\)</EquationSource> </InlineEquation>. On the other hand, we obtain a full characterization of when <InlineEquation ID="IEq12"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13348_2025_494_Article_IEq12.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="88" /> </InlineMediaObject> <EquationSource Format="TEX">\(\Bbbk [X]/P_2(X)\)</EquationSource> </InlineEquation> is <i>F</i>-pure or <i>F</i>-regular, when <InlineEquation ID="IEq13"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13348_2025_494_Article_IEq9.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="75" /> </InlineMediaObject> <EquationSource Format="TEX">\({{\,\textrm{char}\,}}\Bbbk &gt;2\)</EquationSource> </InlineEquation>, and the answer is different than that in even characteristic.</p>

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The F-singularities of algebras defined by permanents

  • Trung Chau

摘要

Let X be a matrix of indeterminates, t an integer, and \(P_t(X)\) define the ideal generated by the permanents of all \(t\times t\) submatrix of X. \(P_t(X)\) is called a permanental ideal. In this article, we study the algebras \(\Bbbk [X]/P_t(X)\) where X is a generic, symmetric, or a Hankel matrix of indeterminates. When \({{\,\textrm{char}\,}}\Bbbk = 2\) , \(P_t(X)\) is also known as a determinantal ideal, a popular class in commutative algebra and algebraic geometry, and thus many properties of \(P_t(X)\) are known in this case. We prove that, if X is an \(n\times n\) matrix and \({{\,\textrm{char}\,}}\Bbbk >2\) , the algebra \(\Bbbk [X]/P_n(X)\) is F-regular, just like when \({{\,\textrm{char}\,}}\Bbbk = 2\) . On the other hand, we obtain a full characterization of when \(\Bbbk [X]/P_2(X)\) is F-pure or F-regular, when \({{\,\textrm{char}\,}}\Bbbk >2\) , and the answer is different than that in even characteristic.