<p>The Rankin constant <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1654_Article_IEq1.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="27" /> </InlineMediaObject> <EquationSource Format="TEX">\(\gamma _{n,l}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>γ</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>l</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> measures the largest volume of the densest sublattice of rank <i>l</i> of a lattice <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1654_Article_IEq2.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="52" /> </InlineMediaObject> <EquationSource Format="TEX">\(\Lambda \in {\mathbb {R}}^n\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi mathvariant="normal">Λ</mi> <mo>∈</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>n</mi> </msup> </mrow> </math></EquationSource> </InlineEquation> over all such lattices of rank <i>n</i>. The Bergé-Martinet constant <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1654_Article_IEq3.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="27" /> </InlineMediaObject> <EquationSource Format="TEX">\(\gamma '_{n,l}\)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>γ</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>l</mi> </mrow> <mo>′</mo> </msubsup> </math></EquationSource> </InlineEquation> is a variation that takes into account the dual lattice. Exact values and bounds for both constants are mostly open in general. We consider the case of lattices built from linear codes, and look at bounds on <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1654_Article_IEq1.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="27" /> </InlineMediaObject> <EquationSource Format="TEX">\(\gamma _{n,l}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>γ</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>l</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1654_Article_IEq3.gif" Format="GIF" Height="22" Rendition="HTML" Resolution="72" Type="Linedraw" Width="27" /> </InlineMediaObject> <EquationSource Format="TEX">\(\gamma '_{n,l}\)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>γ</mi> <mrow> <mi>n</mi> <mo>,</mo> <mi>l</mi> </mrow> <mo>′</mo> </msubsup> </math></EquationSource> </InlineEquation>. In particular, we revisit known results for <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1654_Article_IEq6.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="88" /> </InlineMediaObject> <EquationSource Format="TEX">\(n=3,4,5,8\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>n</mi> <mo>=</mo> <mn>3</mn> <mo>,</mo> <mn>4</mn> <mo>,</mo> <mn>5</mn> <mo>,</mo> <mn>8</mn> </mrow> </math></EquationSource> </InlineEquation> and give lower and upper bounds for the open cases <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1654_Article_IEq7.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="58" /> </InlineMediaObject> <EquationSource Format="TEX">\(\gamma _{5,2},\gamma _{7,2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>γ</mi> <mrow> <mn>5</mn> <mo>,</mo> <mn>2</mn> </mrow> </msub> <mo>,</mo> <msub> <mi>γ</mi> <mrow> <mn>7</mn> <mo>,</mo> <mn>2</mn> </mrow> </msub> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1654_Article_IEq8.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="58" /> </InlineMediaObject> <EquationSource Format="TEX">\(\gamma '_{5,2},\gamma '_{7,2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mi>γ</mi> <mrow> <mn>5</mn> <mo>,</mo> <mn>2</mn> </mrow> <mo>′</mo> </msubsup> <mo>,</mo> <msubsup> <mi>γ</mi> <mrow> <mn>7</mn> <mo>,</mo> <mn>2</mn> </mrow> <mo>′</mo> </msubsup> </mrow> </math></EquationSource> </InlineEquation>.</p>

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About the Rankin and Bergé-Martinet constants from a coding theory view point

  • Frédérique Oggier,
  • Shengwei Liu,
  • Hongwei Liu

摘要

The Rankin constant \(\gamma _{n,l}\) γ n , l measures the largest volume of the densest sublattice of rank l of a lattice \(\Lambda \in {\mathbb {R}}^n\) Λ R n over all such lattices of rank n. The Bergé-Martinet constant \(\gamma '_{n,l}\) γ n , l is a variation that takes into account the dual lattice. Exact values and bounds for both constants are mostly open in general. We consider the case of lattices built from linear codes, and look at bounds on \(\gamma _{n,l}\) γ n , l and \(\gamma '_{n,l}\) γ n , l . In particular, we revisit known results for \(n=3,4,5,8\) n = 3 , 4 , 5 , 8 and give lower and upper bounds for the open cases \(\gamma _{5,2},\gamma _{7,2}\) γ 5 , 2 , γ 7 , 2 and \(\gamma '_{5,2},\gamma '_{7,2}\) γ 5 , 2 , γ 7 , 2 .