<p>This paper explores the leading terms of equivariant Artin <i>L</i>-functions at <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(s=0\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>s</mi> <mo>=</mo> <mn>0</mn> </mrow> </math></EquationSource> </InlineEquation> for finite abelian extensions <i>F</i>/<i>k</i>, where <i>k</i> is an imaginary quadratic number field. We introduce a module constructed from these leading terms and the Dirichlet regulator, and compute its generalized index relative to the torsion-free part of the unit group of <i>F</i>. The main result establishes that this index equals the ratio of class numbers <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(h_F/h_k\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>h</mi> <mi>F</mi> </msub> <mo stretchy="false">/</mo> <msub> <mi>h</mi> <mi>k</mi> </msub> </mrow> </math></EquationSource> </InlineEquation> multiplied by an explicit annihilator index involving roots of unity. For primes <i>p</i> not dividing the Galois group order, we provide a <i>p</i>-adic refinement using idempotents from higher Stark theory. As consequences, we derive obstructions to the existence of integral higher Stark elements mapping to the equivariant <i>L</i>-value and prove class number divisibility under non-decomposition conditions for ramified places. These findings contribute to the verification of equivariant Stark-type conjectures and offer new insights into class number relations in abelian extensions.</p>

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Class number relations in almost abelian number fields

  • Saad El Boukhari

摘要

This paper explores the leading terms of equivariant Artin L-functions at \(s=0\) s = 0 for finite abelian extensions F/k, where k is an imaginary quadratic number field. We introduce a module constructed from these leading terms and the Dirichlet regulator, and compute its generalized index relative to the torsion-free part of the unit group of F. The main result establishes that this index equals the ratio of class numbers \(h_F/h_k\) h F / h k multiplied by an explicit annihilator index involving roots of unity. For primes p not dividing the Galois group order, we provide a p-adic refinement using idempotents from higher Stark theory. As consequences, we derive obstructions to the existence of integral higher Stark elements mapping to the equivariant L-value and prove class number divisibility under non-decomposition conditions for ramified places. These findings contribute to the verification of equivariant Stark-type conjectures and offer new insights into class number relations in abelian extensions.