Elements of : closure of times prime-to- torsion
ProvedLeopoldt.mem_unitClosure_iffleopoldtnumber-theory
Let be a prime, a number field, the semilocal units at , the diagonal embedding of the global units, and (the platform's unitClosure). Then if and only if where lies in the topological closure of in and is a torsion element of order prime to . In other words
where denotes the prime-to- torsion of . This corrects the identification in the source: the intersection may be strictly larger (e.g. , gives versus ), though only by a finite group, so the -ranks agree.
Preamble
import Definitions.Def_LeopoldtDefect
Formal statement
namespace Leopoldt
theorem mem_unitClosure_iff (p : ℕ) [Fact p.Prime] (K : Type*) [Field K] [NumberField K]
(u : SemilocalUnits p K) :
u ∈ unitClosure p K ↔ ∃ c ∈ closure (Set.range (diagonalUnits p K)),
∃ t : SemilocalUnits p K, (∃ m : ℕ, m.Coprime p ∧ t ^ m = 1) ∧ c * t = u := by sorry
end LeopoldtSource
P. Mihăilescu, On CM Z_p-extensions and the Leopoldt conjecture for CM fields, arXiv:1105.4544, §1.1, p.3 (definition of Ē = ⋂_n ι(E)·U^{p^n}); J. Neukirch, Algebraic Number Theory, Ch. II, Prop. 5.7 (structure U ≅ μ_{q-1} × U^{(1)} of local units, U^{(1)} a finitely generated ℤ_p-module).