<p>Consider a finite field <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_844_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathbb {F}_q\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="double-struck">F</mi> <mi>q</mi> </msub> </math></EquationSource> </InlineEquation> and positive integers <i>d</i>,&#xa0;<i>m</i>,&#xa0;<i>r</i> with <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_844_Article_IEq2.gif" Format="GIF" Height="43" Rendition="HTML" Resolution="72" Type="Linedraw" Width="142" /> </InlineMediaObject> <EquationSource Format="TEX">\(1\leqslant r\leqslant \left( {\begin{array}{c}m+d\\ d\end{array}}\right) \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>1</mn> <mo>⩽</mo> <mi>r</mi> <mo>⩽</mo> <mfenced close=")" open="("> <mrow> <mtable> <mtr> <mtd> <mrow> <mi>m</mi> <mo>+</mo> <mi>d</mi> </mrow> </mtd> </mtr> <mtr> <mtd> <mrow> <mrow /> <mi>d</mi> </mrow> </mtd> </mtr> </mtable> </mrow> </mfenced> </mrow> </math></EquationSource> </InlineEquation>. Let <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_844_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="46" /> </InlineMediaObject> <EquationSource Format="TEX">\(S_d(m)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>S</mi> <mi>d</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>m</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> be the <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_844_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathbb {F}_q\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="double-struck">F</mi> <mi>q</mi> </msub> </math></EquationSource> </InlineEquation> vector space of all homogeneous polynomials of degree <i>d</i> in <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_844_Article_IEq5.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="85" /> </InlineMediaObject> <EquationSource Format="TEX">\(X_0,\dots ,X_m\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>X</mi> <mn>0</mn> </msub> <mo>,</mo> <mo>⋯</mo> <mo>,</mo> <msub> <mi>X</mi> <mi>m</mi> </msub> </mrow> </math></EquationSource> </InlineEquation>. Let <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_844_Article_IEq6.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="59" /> </InlineMediaObject> <EquationSource Format="TEX">\(e_r(d,m)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>e</mi> <mi>r</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>d</mi> <mo>,</mo> <mi>m</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> be the maximum number of <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_844_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathbb {F}_q\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="double-struck">F</mi> <mi>q</mi> </msub> </math></EquationSource> </InlineEquation>-rational points in the vanishing set of <i>W</i> as <i>W</i> varies through all subspaces of <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_844_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="46" /> </InlineMediaObject> <EquationSource Format="TEX">\(S_d(m)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>S</mi> <mi>d</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>m</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> of dimension <i>r</i>. Beelen, Datta, and Ghorpade conjectured an exact formula of <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_844_Article_IEq6.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="59" /> </InlineMediaObject> <EquationSource Format="TEX">\(e_r(d,m)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>e</mi> <mi>r</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>d</mi> <mo>,</mo> <mi>m</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> when <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_844_Article_IEq10.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="70" /> </InlineMediaObject> <EquationSource Format="TEX">\(q\geqslant d+1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>q</mi> <mo>⩾</mo> <mi>d</mi> <mo>+</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation>. We prove that their conjectured formula is true when <i>q</i> is sufficiently large in terms of <i>m</i>, <i>d</i>, <i>r</i>. The problem of determining <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_844_Article_IEq6.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="59" /> </InlineMediaObject> <EquationSource Format="TEX">\(e_r(d,m)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>e</mi> <mi>r</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>d</mi> <mo>,</mo> <mi>m</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> is equivalent to the problem of computing the <InlineEquation ID="IEq12"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_844_Article_IEq12.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="21" /> </InlineMediaObject> <EquationSource Format="TEX">\(r^\textrm{th}\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>r</mi> <mtext>th</mtext> </msup> </math></EquationSource> </InlineEquation> generalized Hamming weight of the projective Reed–Muller code <InlineEquation ID="IEq13"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_844_Article_IEq13.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="89" /> </InlineMediaObject> <EquationSource Format="TEX">\(\textrm{PRM}_q(d,m)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mtext>PRM</mtext> <mi>q</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>d</mi> <mo>,</mo> <mi>m</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>. It is also equivalent to the problem of determining the maximum number of points on sections of Veronese varieties by linear subvarieties of codimension <i>r</i>.</p>

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On a conjecture of Beelen, Datta and Ghorpade for the number of points of varieties over finite fields

  • Deepesh Singhal,
  • Yuxin Lin

摘要

Consider a finite field \(\mathbb {F}_q\) F q and positive integers dmr with \(1\leqslant r\leqslant \left( {\begin{array}{c}m+d\\ d\end{array}}\right) \) 1 r m + d d . Let \(S_d(m)\) S d ( m ) be the \(\mathbb {F}_q\) F q vector space of all homogeneous polynomials of degree d in \(X_0,\dots ,X_m\) X 0 , , X m . Let \(e_r(d,m)\) e r ( d , m ) be the maximum number of \(\mathbb {F}_q\) F q -rational points in the vanishing set of W as W varies through all subspaces of \(S_d(m)\) S d ( m ) of dimension r. Beelen, Datta, and Ghorpade conjectured an exact formula of \(e_r(d,m)\) e r ( d , m ) when \(q\geqslant d+1\) q d + 1 . We prove that their conjectured formula is true when q is sufficiently large in terms of m, d, r. The problem of determining \(e_r(d,m)\) e r ( d , m ) is equivalent to the problem of computing the \(r^\textrm{th}\) r th generalized Hamming weight of the projective Reed–Muller code \(\textrm{PRM}_q(d,m)\) PRM q ( d , m ) . It is also equivalent to the problem of determining the maximum number of points on sections of Veronese varieties by linear subvarieties of codimension r.