<p>We study holomorphic maps <i>F</i> from a smooth Levi non-degenerate real hypersurface <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="208_2025_3134_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="65" /> </InlineMediaObject> <EquationSource Format="TEX">\( M_{\ell }\subset {\mathbb {C}}^n \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>M</mi> <mi>ℓ</mi> </msub> <mo>⊂</mo> <msup> <mrow> <mi mathvariant="double-struck">C</mi> </mrow> <mi>n</mi> </msup> </mrow> </math></EquationSource> </InlineEquation> into a hyperquadric <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="208_2025_3134_Article_IEq2.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="25" /> </InlineMediaObject> <EquationSource Format="TEX">\( {\mathbb {H}}_{\ell '}^N \)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi mathvariant="double-struck">H</mi> <mrow> <msup> <mi>ℓ</mi> <mo>′</mo> </msup> </mrow> <mi>N</mi> </msubsup> </math></EquationSource> </InlineEquation> with signatures <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="208_2025_3134_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="99" /> </InlineMediaObject> <EquationSource Format="TEX">\( \ell \le (n-1)/2 \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ℓ</mi> <mo>≤</mo> <mo stretchy="false">(</mo> <mi>n</mi> <mo>-</mo> <mn>1</mn> <mo stretchy="false">)</mo> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="208_2025_3134_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="113" /> </InlineMediaObject> <EquationSource Format="TEX">\( \ell '\le (N-1)/2,\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>ℓ</mi> <mo>′</mo> </msup> <mo>≤</mo> <mrow> <mo stretchy="false">(</mo> <mi>N</mi> <mo>-</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">/</mo> <mn>2</mn> <mo>,</mo> </mrow> </math></EquationSource> </InlineEquation> respectively. Assuming that <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="208_2025_3134_Article_IEq5.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="115" /> </InlineMediaObject> <EquationSource Format="TEX">\( N - n &lt; n - 1,\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>N</mi> <mo>-</mo> <mi>n</mi> <mo>&lt;</mo> <mi>n</mi> <mo>-</mo> <mn>1</mn> <mo>,</mo> </mrow> </math></EquationSource> </InlineEquation> we prove that if <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="208_2025_3134_Article_IEq6.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="47" /> </InlineMediaObject> <EquationSource Format="TEX">\( \ell = \ell ',\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ℓ</mi> <mo>=</mo> <msup> <mi>ℓ</mi> <mo>′</mo> </msup> <mo>,</mo> </mrow> </math></EquationSource> </InlineEquation> then <i>F</i> is either CR transversal to <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="208_2025_3134_Article_IEq7.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="25" /> </InlineMediaObject> <EquationSource Format="TEX">\( {\mathbb {H}}_{\ell }^N \)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi mathvariant="double-struck">H</mi> <mrow> <mi>ℓ</mi> </mrow> <mi>N</mi> </msubsup> </math></EquationSource> </InlineEquation> at every point of <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="208_2025_3134_Article_IEq8.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="29" /> </InlineMediaObject> <EquationSource Format="TEX">\( M_{\ell },\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>M</mi> <mi>ℓ</mi> </msub> <mo>,</mo> </mrow> </math></EquationSource> </InlineEquation> or it maps a neighborhood of <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="208_2025_3134_Article_IEq9.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="25" /> </InlineMediaObject> <EquationSource Format="TEX">\( M_{\ell } \)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>M</mi> <mi>ℓ</mi> </msub> </math></EquationSource> </InlineEquation> in <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="208_2025_3134_Article_IEq10.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="21" /> </InlineMediaObject> <EquationSource Format="TEX">\( {\mathbb {C}}^n \)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi mathvariant="double-struck">C</mi> </mrow> <mi>n</mi> </msup> </math></EquationSource> </InlineEquation> into <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="208_2025_3134_Article_IEq11.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="30" /> </InlineMediaObject> <EquationSource Format="TEX">\( {\mathbb {H}}_{\ell }^N.\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mi mathvariant="double-struck">H</mi> <mrow> <mi>ℓ</mi> </mrow> <mi>N</mi> </msubsup> <mo>.</mo> </mrow> </math></EquationSource> </InlineEquation> Furthermore, in the case where <InlineEquation ID="IEq12"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="208_2025_3134_Article_IEq12.gif" Format="GIF" Height="18" Rendition="HTML" Resolution="72" Type="Linedraw" Width="47" /> </InlineMediaObject> <EquationSource Format="TEX">\( \ell ' &gt; \ell ,\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>ℓ</mi> <mo>′</mo> </msup> <mo>&gt;</mo> <mi>ℓ</mi> <mo>,</mo> </mrow> </math></EquationSource> </InlineEquation> we show that if <i>F</i> is not CR transversal at <InlineEquation ID="IEq13"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="208_2025_3134_Article_IEq13.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="57" /> </InlineMediaObject> <EquationSource Format="TEX">\(0\in M_\ell ,\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>0</mn> <mo>∈</mo> <msub> <mi>M</mi> <mi>ℓ</mi> </msub> <mo>,</mo> </mrow> </math></EquationSource> </InlineEquation> then it must be transversally flat. The latter is best possible.</p>

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Transversality of holomorphic maps into hyperquadrics

  • Xiaojun Huang,
  • Weixia Zhu

摘要

We study holomorphic maps F from a smooth Levi non-degenerate real hypersurface \( M_{\ell }\subset {\mathbb {C}}^n \) M C n into a hyperquadric \( {\mathbb {H}}_{\ell '}^N \) H N with signatures \( \ell \le (n-1)/2 \) ( n - 1 ) / 2 and \( \ell '\le (N-1)/2,\) ( N - 1 ) / 2 , respectively. Assuming that \( N - n < n - 1,\) N - n < n - 1 , we prove that if \( \ell = \ell ',\) = , then F is either CR transversal to \( {\mathbb {H}}_{\ell }^N \) H N at every point of \( M_{\ell },\) M , or it maps a neighborhood of \( M_{\ell } \) M in \( {\mathbb {C}}^n \) C n into \( {\mathbb {H}}_{\ell }^N.\) H N . Furthermore, in the case where \( \ell ' > \ell ,\) > , we show that if F is not CR transversal at \(0\in M_\ell ,\) 0 M , then it must be transversally flat. The latter is best possible.