<p>Motivated by a theorem of Silverman, we consider the following problem. Let <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(A\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>A</mi> </math></EquationSource> </InlineEquation> be an abelian variety over a global field <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(K\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>K</mi> </math></EquationSource> </InlineEquation>. Given a non-torsion point <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(P \in A(K)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>P</mi> <mo>∈</mo> <mi>A</mi> <mo stretchy="false">(</mo> <mi>K</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>, for a sufficiently large positive integer <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(n\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>n</mi> </math></EquationSource> </InlineEquation>, whether there exists a place <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(v\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>v</mi> </math></EquationSource> </InlineEquation> of <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(K\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>K</mi> </math></EquationSource> </InlineEquation> such that the order of the reduction of <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(P\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>P</mi> </math></EquationSource> </InlineEquation> modulo <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(v\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>v</mi> </math></EquationSource> </InlineEquation> is <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(n\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>n</mi> </math></EquationSource> </InlineEquation>? In this article, we first show that this holds for an elliptic curve over a global function field of positive characteristic <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(p&gt;3\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>p</mi> <mo>&gt;</mo> <mn>3</mn> </mrow> </math></EquationSource> </InlineEquation> and for sufficiently large positive integers <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(n\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>n</mi> </math></EquationSource> </InlineEquation> coprime to <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\(p\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>p</mi> </math></EquationSource> </InlineEquation>. In the second part of the paper, we consider its relative version over <InlineEquation ID="IEq13"> <EquationSource Format="TEX">\(\mathbb {C}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="double-struck">C</mi> </math></EquationSource> </InlineEquation>. More precisely, let <InlineEquation ID="IEq14"> <EquationSource Format="TEX">\(\pi : \mathcal {A} \rightarrow S\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>π</mi> <mo>:</mo> <mi mathvariant="script">A</mi> <mo stretchy="false">→</mo> <mi>S</mi> </mrow> </math></EquationSource> </InlineEquation> be an abelian scheme over some variety <InlineEquation ID="IEq15"> <EquationSource Format="TEX">\(S\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>S</mi> </math></EquationSource> </InlineEquation> over <InlineEquation ID="IEq16"> <EquationSource Format="TEX">\(\mathbb {C}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="double-struck">C</mi> </math></EquationSource> </InlineEquation>, and let <InlineEquation ID="IEq17"> <EquationSource Format="TEX">\(P\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>P</mi> </math></EquationSource> </InlineEquation> be a non-torsion section of <InlineEquation ID="IEq18"> <EquationSource Format="TEX">\(\pi \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>π</mi> </math></EquationSource> </InlineEquation>. If the Betti map associated to <InlineEquation ID="IEq19"> <EquationSource Format="TEX">\(P\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>P</mi> </math></EquationSource> </InlineEquation> is generically submersive, then for every sufficiently large <InlineEquation ID="IEq20"> <EquationSource Format="TEX">\(n\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>n</mi> </math></EquationSource> </InlineEquation>, there is a point <InlineEquation ID="IEq21"> <EquationSource Format="TEX">\(s\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>s</mi> </math></EquationSource> </InlineEquation> in <InlineEquation ID="IEq22"> <EquationSource Format="TEX">\(S(\mathbb {C})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>S</mi> <mo stretchy="false">(</mo> <mi mathvariant="double-struck">C</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> such that <InlineEquation ID="IEq23"> <EquationSource Format="TEX">\(P(s)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>P</mi> <mo stretchy="false">(</mo> <mi>s</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> is a point of order <InlineEquation ID="IEq24"> <EquationSource Format="TEX">\(n\)</EquationSource> <EquationSource Format="MATHML"><math> <mi>n</mi> </math></EquationSource> </InlineEquation> in the corresponding fiber.</p>

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Remarks on a theorem of Silverman

  • Khai-Hoan Nguyen-Dang,
  • Quang-Khai Nguyen

摘要

Motivated by a theorem of Silverman, we consider the following problem. Let \(A\) A be an abelian variety over a global field \(K\) K . Given a non-torsion point \(P \in A(K)\) P A ( K ) , for a sufficiently large positive integer \(n\) n , whether there exists a place \(v\) v of \(K\) K such that the order of the reduction of \(P\) P modulo \(v\) v is \(n\) n ? In this article, we first show that this holds for an elliptic curve over a global function field of positive characteristic \(p>3\) p > 3 and for sufficiently large positive integers \(n\) n coprime to \(p\) p . In the second part of the paper, we consider its relative version over \(\mathbb {C}\) C . More precisely, let \(\pi : \mathcal {A} \rightarrow S\) π : A S be an abelian scheme over some variety \(S\) S over \(\mathbb {C}\) C , and let \(P\) P be a non-torsion section of \(\pi \) π . If the Betti map associated to \(P\) P is generically submersive, then for every sufficiently large \(n\) n , there is a point \(s\) s in \(S(\mathbb {C})\) S ( C ) such that \(P(s)\) P ( s ) is a point of order \(n\) n in the corresponding fiber.