<p>In this paper, we study equi-centro-affine extremal hypersurfaces in an ellipsoid. By investigating the evolution of invariant submanifold flows under centro-affine unimodular transformations, we derive the first and second variational formulas for the associated invariant area. Stability analysis reveals that the circles with radius <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="209_2025_3735_Article_IEq1.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="70" /> </InlineMediaObject> <EquationSource Format="TEX">\(r=\sqrt{6}/3\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>r</mi> <mo>=</mo> <msqrt> <mn>6</mn> </msqrt> <mo stretchy="false">/</mo> <mn>3</mn> </mrow> </math></EquationSource> </InlineEquation> on <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="209_2025_3735_Article_IEq2.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="38" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathbb {S}}^2(1)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mrow> <mi mathvariant="double-struck">S</mi> </mrow> <mn>2</mn> </msup> <mrow> <mo stretchy="false">(</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> are characterized as being equi-centro-affine maximal. Moreover, we provide a classification of the compact isoparametric equi-centro-affine extremal hypersurfaces on <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="209_2025_3735_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="52" /> </InlineMediaObject> <EquationSource Format="TEX">\((n+1)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mi>n</mi> <mo>+</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>-dimensional sphere, as well as the generalized closed equi-centro-affine extremal curves on 2-dimensional sphere. These curves are shown to belong to a family of transcendental curves <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="209_2025_3735_Article_IEq4.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="26" /> </InlineMediaObject> <EquationSource Format="TEX">\(\textrm{x}_{p,q}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mtext>x</mtext> <mrow> <mi>p</mi> <mo>,</mo> <mi>q</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> (<i>p</i> and <i>q</i> are two coprime positive integers satisfying that <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="209_2025_3735_Article_IEq5.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="104" /> </InlineMediaObject> <EquationSource Format="TEX">\(1/2&lt;p/q&lt;1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>1</mn> <mo stretchy="false">/</mo> <mn>2</mn> <mo>&lt;</mo> <mi>p</mi> <mo stretchy="false">/</mo> <mi>q</mi> <mo>&lt;</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation>). In addition, we establish an equi-centro-affine version of isoperimetric inequality on <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="209_2025_3735_Article_IEq2.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="38" /> </InlineMediaObject> <EquationSource Format="TEX">\({\mathbb {S}}^2(1)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mrow> <mi mathvariant="double-struck">S</mi> </mrow> <mn>2</mn> </msup> <mrow> <mo stretchy="false">(</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> under certain assumptions.</p>

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Equi-centro-affine extremal hypersurfaces in ellipsoid

  • Yun Yang,
  • Changzheng Qu

摘要

In this paper, we study equi-centro-affine extremal hypersurfaces in an ellipsoid. By investigating the evolution of invariant submanifold flows under centro-affine unimodular transformations, we derive the first and second variational formulas for the associated invariant area. Stability analysis reveals that the circles with radius \(r=\sqrt{6}/3\) r = 6 / 3 on \({\mathbb {S}}^2(1)\) S 2 ( 1 ) are characterized as being equi-centro-affine maximal. Moreover, we provide a classification of the compact isoparametric equi-centro-affine extremal hypersurfaces on \((n+1)\) ( n + 1 ) -dimensional sphere, as well as the generalized closed equi-centro-affine extremal curves on 2-dimensional sphere. These curves are shown to belong to a family of transcendental curves \(\textrm{x}_{p,q}\) x p , q (p and q are two coprime positive integers satisfying that \(1/2<p/q<1\) 1 / 2 < p / q < 1 ). In addition, we establish an equi-centro-affine version of isoperimetric inequality on \({\mathbb {S}}^2(1)\) S 2 ( 1 ) under certain assumptions.