<p>We construct a family of cyclic completely regular codes (CRCs) of length <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(n=2^m-1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>n</mi> <mo>=</mo> <msup> <mn>2</mn> <mi>m</mi> </msup> <mo>-</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation> and compute their intersection arrays. These codes, denoted <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(C_{1,5}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>C</mi> <mrow> <mn>1</mn> <mo>,</mo> <mn>5</mn> </mrow> </msub> </math></EquationSource> </InlineEquation>, are generated by the product <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(m_1(x)m_5(x)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>m</mi> <mn>1</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> <msub> <mi>m</mi> <mn>5</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, where <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(m_i(x)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>m</mi> <mi>i</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> is the minimal polynomial of <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(\alpha ^i\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>α</mi> <mi>i</mi> </msup> </math></EquationSource> </InlineEquation>, and <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(\alpha \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>α</mi> </math></EquationSource> </InlineEquation> is a primitive element of the finite field <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(\mathbb {F}_{2^m}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi mathvariant="double-struck">F</mi> <msup> <mn>2</mn> <mi>m</mi> </msup> </msub> </math></EquationSource> </InlineEquation>. We consider two main cases: odd <i>m</i> and <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(m \equiv 2 \pmod {4}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>m</mi> <mo>≡</mo> <mn>2</mn> <mspace width="4.44443pt" /> <mo stretchy="false">(</mo> <mo>mod</mo> <mspace width="0.277778em" /> <mn>4</mn> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>. For odd <i>m</i>, these codes are known to be completely regular with covering radius <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(\rho =3\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ρ</mi> <mo>=</mo> <mn>3</mn> </mrow> </math></EquationSource> </InlineEquation> and minimum distance <InlineEquation ID="IEq13"> <EquationSource Format="TEX">\(d=5\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>d</mi> <mo>=</mo> <mn>5</mn> </mrow> </math></EquationSource> </InlineEquation>. We prove that, for any <i>m</i>, the codes <InlineEquation ID="IEq14"> <EquationSource Format="TEX">\(C_{1,3}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>C</mi> <mrow> <mn>1</mn> <mo>,</mo> <mn>3</mn> </mrow> </msub> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq15"> <EquationSource Format="TEX">\(C_{1,5}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>C</mi> <mrow> <mn>1</mn> <mo>,</mo> <mn>5</mn> </mrow> </msub> </math></EquationSource> </InlineEquation> are non-equivalent despite sharing the same parameters and intersection array. For <InlineEquation ID="IEq16"> <EquationSource Format="TEX">\(m \equiv 2 \pmod {4}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>m</mi> <mo>≡</mo> <mn>2</mn> <mspace width="4.44443pt" /> <mo stretchy="false">(</mo> <mo>mod</mo> <mspace width="0.277778em" /> <mn>4</mn> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>, we demonstrate that <InlineEquation ID="IEq17"> <EquationSource Format="TEX">\(C_{1,5}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>C</mi> <mrow> <mn>1</mn> <mo>,</mo> <mn>5</mn> </mrow> </msub> </math></EquationSource> </InlineEquation> forms a new family of completely regular codes with covering radius <InlineEquation ID="IEq18"> <EquationSource Format="TEX">\(\rho =3\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ρ</mi> <mo>=</mo> <mn>3</mn> </mrow> </math></EquationSource> </InlineEquation>, minimum distance <InlineEquation ID="IEq19"> <EquationSource Format="TEX">\(d=3\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>d</mi> <mo>=</mo> <mn>3</mn> </mrow> </math></EquationSource> </InlineEquation>, and intersection array <InlineEquation ID="IEq20"> <EquationSource Format="TEX">\(\operatorname {IA}=[n, n-3, \frac{3n+7}{4}; 1, 4, \frac{n-3}{4}]\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>IA</mo> <mo>=</mo> <mo stretchy="false">[</mo> <mi>n</mi> <mo>,</mo> <mi>n</mi> <mo>-</mo> <mn>3</mn> <mo>,</mo> <mfrac> <mrow> <mn>3</mn> <mi>n</mi> <mo>+</mo> <mn>7</mn> </mrow> <mn>4</mn> </mfrac> <mo>;</mo> <mn>1</mn> <mo>,</mo> <mn>4</mn> <mo>,</mo> <mfrac> <mrow> <mi>n</mi> <mo>-</mo> <mn>3</mn> </mrow> <mn>4</mn> </mfrac> <mo stretchy="false">]</mo> </mrow> </math></EquationSource> </InlineEquation>. Moreover, the corresponding extended cyclic codes <InlineEquation ID="IEq21"> <EquationSource Format="TEX">\(C_{1,5}^*\)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>C</mi> <mrow> <mn>1</mn> <mo>,</mo> <mn>5</mn> </mrow> <mo>∗</mo> </msubsup> </math></EquationSource> </InlineEquation> are completely regular <InlineEquation ID="IEq22"> <EquationSource Format="TEX">\([n+1, n-2m, 4; 4]\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">[</mo> <mi>n</mi> <mo>+</mo> <mn>1</mn> <mo>,</mo> <mi>n</mi> <mo>-</mo> <mn>2</mn> <mi>m</mi> <mo>,</mo> <mn>4</mn> <mo>;</mo> <mn>4</mn> <mo stretchy="false">]</mo> </mrow> </math></EquationSource> </InlineEquation>-codes with intersection array <InlineEquation ID="IEq23"> <EquationSource Format="TEX">\(\operatorname {IA}=[n+1, n, n-3, \frac{3n+7}{4}; 1, 4, \frac{n-3}{4}, n+1]\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>IA</mo> <mo>=</mo> <mo stretchy="false">[</mo> <mi>n</mi> <mo>+</mo> <mn>1</mn> <mo>,</mo> <mi>n</mi> <mo>,</mo> <mi>n</mi> <mo>-</mo> <mn>3</mn> <mo>,</mo> <mfrac> <mrow> <mn>3</mn> <mi>n</mi> <mo>+</mo> <mn>7</mn> </mrow> <mn>4</mn> </mfrac> <mo>;</mo> <mn>1</mn> <mo>,</mo> <mn>4</mn> <mo>,</mo> <mfrac> <mrow> <mi>n</mi> <mo>-</mo> <mn>3</mn> </mrow> <mn>4</mn> </mfrac> <mo>,</mo> <mi>n</mi> <mo>+</mo> <mn>1</mn> <mo stretchy="false">]</mo> </mrow> </math></EquationSource> </InlineEquation>. We also describe the parameters and some properties of the coset graphs associated to these completely regular codes which form distance-regular graphs.</p>

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Cyclic completely regular codes \(C_{1,5}\)

  • Josep Rifà,
  • Victor Zinoviev

摘要

We construct a family of cyclic completely regular codes (CRCs) of length \(n=2^m-1\) n = 2 m - 1 and compute their intersection arrays. These codes, denoted \(C_{1,5}\) C 1 , 5 , are generated by the product \(m_1(x)m_5(x)\) m 1 ( x ) m 5 ( x ) , where \(m_i(x)\) m i ( x ) is the minimal polynomial of \(\alpha ^i\) α i , and \(\alpha \) α is a primitive element of the finite field \(\mathbb {F}_{2^m}\) F 2 m . We consider two main cases: odd m and \(m \equiv 2 \pmod {4}\) m 2 ( mod 4 ) . For odd m, these codes are known to be completely regular with covering radius \(\rho =3\) ρ = 3 and minimum distance \(d=5\) d = 5 . We prove that, for any m, the codes \(C_{1,3}\) C 1 , 3 and \(C_{1,5}\) C 1 , 5 are non-equivalent despite sharing the same parameters and intersection array. For \(m \equiv 2 \pmod {4}\) m 2 ( mod 4 ) , we demonstrate that \(C_{1,5}\) C 1 , 5 forms a new family of completely regular codes with covering radius \(\rho =3\) ρ = 3 , minimum distance \(d=3\) d = 3 , and intersection array \(\operatorname {IA}=[n, n-3, \frac{3n+7}{4}; 1, 4, \frac{n-3}{4}]\) IA = [ n , n - 3 , 3 n + 7 4 ; 1 , 4 , n - 3 4 ] . Moreover, the corresponding extended cyclic codes \(C_{1,5}^*\) C 1 , 5 are completely regular \([n+1, n-2m, 4; 4]\) [ n + 1 , n - 2 m , 4 ; 4 ] -codes with intersection array \(\operatorname {IA}=[n+1, n, n-3, \frac{3n+7}{4}; 1, 4, \frac{n-3}{4}, n+1]\) IA = [ n + 1 , n , n - 3 , 3 n + 7 4 ; 1 , 4 , n - 3 4 , n + 1 ] . We also describe the parameters and some properties of the coset graphs associated to these completely regular codes which form distance-regular graphs.