<p>Let <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1573_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> be the finite field with <i>q</i> elements, where <i>q</i> is a power of a prime <i>p</i>. Given a monic polynomial <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1573_Article_IEq2.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="68" /> </InlineMediaObject> <EquationSource Format="TEX">\(f \in \mathbb {F}_q[x]\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mo>∈</mo> <msub> <mi mathvariant="double-struck">F</mi> <mi>q</mi> </msub> <mrow> <mo stretchy="false">[</mo> <mi>x</mi> <mo stretchy="false">]</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> that is not divisible by <i>x</i>, there exists a positive integer <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1573_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="62" /> </InlineMediaObject> <EquationSource Format="TEX">\(e=e(f)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>e</mi> <mo>=</mo> <mi>e</mi> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> such that <i>f</i>(<i>x</i>) divides the binomial <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1573_Article_IEq4.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="46" /> </InlineMediaObject> <EquationSource Format="TEX">\(x^e-1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>x</mi> <mi>e</mi> </msup> <mo>-</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation> and <i>e</i> is minimal with this property. The integer <i>e</i> is commonly known as the order of <i>f</i> and we write <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1573_Article_IEq5.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="79" /> </InlineMediaObject> <EquationSource Format="TEX">\(\textrm{ord}(f)=e\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mtext>ord</mtext> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mi>e</mi> </mrow> </math></EquationSource> </InlineEquation>. Motivated by a recent work of the second author on primitive <i>k</i>-normal elements over finite fields, in this paper we introduce the concept of polynomials free of binomials. These are the polynomials <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1573_Article_IEq2.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="68" /> </InlineMediaObject> <EquationSource Format="TEX">\(f \in \mathbb {F}_q[x]\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mo>∈</mo> <msub> <mi mathvariant="double-struck">F</mi> <mi>q</mi> </msub> <mrow> <mo stretchy="false">[</mo> <mi>x</mi> <mo stretchy="false">]</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, not divisible by <i>x</i>, such that <i>f</i>(<i>x</i>) does not divide any binomial <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1573_Article_IEq7.gif" Format="GIF" Height="21" Rendition="HTML" Resolution="72" Type="Linedraw" Width="102" /> </InlineMediaObject> <EquationSource Format="TEX">\(x^d-\delta \in \mathbb {F}_q[x]\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>x</mi> <mi>d</mi> </msup> <mo>-</mo> <mi>δ</mi> <mo>∈</mo> <msub> <mi mathvariant="double-struck">F</mi> <mi>q</mi> </msub> <mrow> <mo stretchy="false">[</mo> <mi>x</mi> <mo stretchy="false">]</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> with <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1573_Article_IEq8.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="110" /> </InlineMediaObject> <EquationSource Format="TEX">\(1\le d&lt;\textrm{ord}(f)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>1</mn> <mo>≤</mo> <mi>d</mi> <mo>&lt;</mo> <mtext>ord</mtext> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>. We obtain some general results on polynomials free of binomials and we focus on the problem of describing the set of degrees of the polynomials that are free of binomials and whose order is fixed. In particular, we completely describe such set when the order equals a positive integer <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1573_Article_IEq9.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="42" /> </InlineMediaObject> <EquationSource Format="TEX">\(n&gt;1\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>n</mi> <mo>&gt;</mo> <mn>1</mn> </mrow> </math></EquationSource> </InlineEquation> whose prime factors divide <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10623_2025_1573_Article_IEq10.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="60" /> </InlineMediaObject> <EquationSource Format="TEX">\(p(q-1)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>p</mi> <mo stretchy="false">(</mo> <mi>q</mi> <mo>-</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>. Moreover, we also provide a correspondence between the polynomials that are free of binomials and cyclic codes that cannot be submerged into smaller constacyclic codes.</p>

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On polynomials over finite fields that are free of binomials

  • Fabio Enrique Brochero Martínez,
  • Lucas Reis,
  • Sávio Ribas

摘要

Let \(\mathbb {F}_q\) F q be the finite field with q elements, where q is a power of a prime p. Given a monic polynomial \(f \in \mathbb {F}_q[x]\) f F q [ x ] that is not divisible by x, there exists a positive integer \(e=e(f)\) e = e ( f ) such that f(x) divides the binomial \(x^e-1\) x e - 1 and e is minimal with this property. The integer e is commonly known as the order of f and we write \(\textrm{ord}(f)=e\) ord ( f ) = e . Motivated by a recent work of the second author on primitive k-normal elements over finite fields, in this paper we introduce the concept of polynomials free of binomials. These are the polynomials \(f \in \mathbb {F}_q[x]\) f F q [ x ] , not divisible by x, such that f(x) does not divide any binomial \(x^d-\delta \in \mathbb {F}_q[x]\) x d - δ F q [ x ] with \(1\le d<\textrm{ord}(f)\) 1 d < ord ( f ) . We obtain some general results on polynomials free of binomials and we focus on the problem of describing the set of degrees of the polynomials that are free of binomials and whose order is fixed. In particular, we completely describe such set when the order equals a positive integer \(n>1\) n > 1 whose prime factors divide \(p(q-1)\) p ( q - 1 ) . Moreover, we also provide a correspondence between the polynomials that are free of binomials and cyclic codes that cannot be submerged into smaller constacyclic codes.