Module

CyclicH2OfTsen.lean

Nyll.AlgebraicCurves.FunctionFields.CyclicH2OfTsen
1 declaration indexed from sourceView source ↗

Cyclic unit H² over curve function fields

Tsen supplies the norm preimages in the existing actual group-cohomology calculation. This is the finite cyclic step, not a claim about all étale cohomology of a curve.

Declarations

AlgebraicCurve.cyclicUnitsH2_eq_zero_of_transcendental_of_finiteDimensional

Actual unit-coefficient H² vanishes for every finite cyclic Galois extension of a one-variable function field over an algebraically closed field.

Source context 1 command

Surrounding namespaces, section variables, and local commands at this declaration.

namespace AlgebraicCurve
theorem cyclicUnitsH2_eq_zero_of_transcendental_of_finiteDimensional
    (K : Type) [Field K] [IsAlgClosed K] {F : Type} [Field F] [Algebra K F]
    (x : F) (hx : Transcendental K x)
    (hfin : FiniteDimensional (IntermediateField.adjoin K ({x} : Set F)) F)
    (hsep : Algebra.IsSeparable (IntermediateField.adjoin K ({x} : Set F)) F)
    (E : Type) [Field E] [Algebra F E] [FiniteDimensional F E]
    [IsGalois F E] [IsCyclic Gal(E/F)]
    (c : groupCohomology (Rep.ofAlgebraAutOnUnits F E) 2) : c = 0