<p>Based on Katz’s equidistribution framework, we give a one-dimensional proof of a function-field analogue of a conjecture of Erdős in the large-<i>q</i> regime: for squarefree <i>f</i> of degree <i>n</i>, every class in <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\((\mathbb {F}_q[t]/(f))^\times \)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mo stretchy="false">(</mo> <msub> <mi mathvariant="double-struck">F</mi> <mi>q</mi> </msub> <mrow> <mo stretchy="false">[</mo> <mi>t</mi> <mo stretchy="false">]</mo> </mrow> <mo stretchy="false">/</mo> <mrow> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">)</mo> </mrow> <mo>×</mo> </msup> </math></EquationSource> </InlineEquation> is represented as a product of two monic irreducibles of degrees <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(\le n\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo>≤</mo> <mi>n</mi> </mrow> </math></EquationSource> </InlineEquation> once <i>q</i> is sufficiently large in terms of <i>n</i>. The proof yields a uniform <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(q^{-1/2}\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>q</mi> <mrow> <mo>-</mo> <mn>1</mn> <mo stretchy="false">/</mo> <mn>2</mn> </mrow> </msup> </math></EquationSource> </InlineEquation>-saving in the relevant twisted character sums, with an explicit constant depending on <i>n</i>. Sawin&#xa0;[12] proved a stronger and more general result by higher-dimensional sheaf-theoretic methods; the present note instead emphasizes a simpler one-dimensional argument within Katz’s framework.</p>

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On a conjecture of Erdős over function fields

  • Likun Xie

摘要

Based on Katz’s equidistribution framework, we give a one-dimensional proof of a function-field analogue of a conjecture of Erdős in the large-q regime: for squarefree f of degree n, every class in \((\mathbb {F}_q[t]/(f))^\times \) ( F q [ t ] / ( f ) ) × is represented as a product of two monic irreducibles of degrees \(\le n\) n once q is sufficiently large in terms of n. The proof yields a uniform \(q^{-1/2}\) q - 1 / 2 -saving in the relevant twisted character sums, with an explicit constant depending on n. Sawin [12] proved a stronger and more general result by higher-dimensional sheaf-theoretic methods; the present note instead emphasizes a simpler one-dimensional argument within Katz’s framework.