<p>Ovoids of the hyperbolic quadric <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(Q^+(7,q)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>Q</mi> <mo>+</mo> </msup> <mrow> <mo stretchy="false">(</mo> <mn>7</mn> <mo>,</mo> <mi>q</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> of <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\textrm{PG}(7, q)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mtext>PG</mtext> <mo stretchy="false">(</mo> <mn>7</mn> <mo>,</mo> <mi>q</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> have been extensively studied over the past 40 years, partly due to their connections with other combinatorial objects. It is well known that the points of an ovoid of <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(Q^+(7,q)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>Q</mi> <mo>+</mo> </msup> <mrow> <mo stretchy="false">(</mo> <mn>7</mn> <mo>,</mo> <mi>q</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> can be parametrized by three polynomials <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(f_1(X,Y, Z)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>f</mi> <mn>1</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>X</mi> <mo>,</mo> <mi>Y</mi> <mo>,</mo> <mi>Z</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(f_2(X,Y, Z)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>f</mi> <mn>2</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>X</mi> <mo>,</mo> <mi>Y</mi> <mo>,</mo> <mi>Z</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(f_3(X,Y, Z)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>f</mi> <mn>3</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>X</mi> <mo>,</mo> <mi>Y</mi> <mo>,</mo> <mi>Z</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>. In this paper, we classify ovoids of <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(Q^+(7,q)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>Q</mi> <mo>+</mo> </msup> <mrow> <mo stretchy="false">(</mo> <mn>7</mn> <mo>,</mo> <mi>q</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> of low degree, specifically under the assumption that <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(f_1(X,Y, Z)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>f</mi> <mn>1</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>X</mi> <mo>,</mo> <mi>Y</mi> <mo>,</mo> <mi>Z</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(f_2(X,Y, Z)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>f</mi> <mn>2</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>X</mi> <mo>,</mo> <mi>Y</mi> <mo>,</mo> <mi>Z</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(f_3(X,Y, Z)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>f</mi> <mn>3</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>X</mi> <mo>,</mo> <mi>Y</mi> <mo>,</mo> <mi>Z</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> have degree at most 3. Our approach relies on the analysis of an algebraic hypersurface associated with the ovoid.</p>

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Ovoids of \(Q^+(7,q)\) of low-degree

  • Daniele Bartoli,
  • Nicola Durante,
  • Giovanni Giuseppe Grimaldi,
  • Marco Timpanella

摘要

Ovoids of the hyperbolic quadric \(Q^+(7,q)\) Q + ( 7 , q ) of \(\textrm{PG}(7, q)\) PG ( 7 , q ) have been extensively studied over the past 40 years, partly due to their connections with other combinatorial objects. It is well known that the points of an ovoid of \(Q^+(7,q)\) Q + ( 7 , q ) can be parametrized by three polynomials \(f_1(X,Y, Z)\) f 1 ( X , Y , Z ) , \(f_2(X,Y, Z)\) f 2 ( X , Y , Z ) , \(f_3(X,Y, Z)\) f 3 ( X , Y , Z ) . In this paper, we classify ovoids of \(Q^+(7,q)\) Q + ( 7 , q ) of low degree, specifically under the assumption that \(f_1(X,Y, Z)\) f 1 ( X , Y , Z ) , \(f_2(X,Y, Z)\) f 2 ( X , Y , Z ) , \(f_3(X,Y, Z)\) f 3 ( X , Y , Z ) have degree at most 3. Our approach relies on the analysis of an algebraic hypersurface associated with the ovoid.