Documentation

Mathlib.RingTheory.DedekindDomain.AdicValuation

Adic valuations on Dedekind domains #

Given a Dedekind domain R of Krull dimension 1 and a maximal ideal v of R, we define the v-adic valuation on R and its extension to the field of fractions K of R. We prove several properties of this valuation, including the existence of uniformizers.

We define the completion of K with respect to the v-adic valuation, denoted v.adicCompletion, and its ring of integers, denoted v.adicCompletionIntegers.

Main definitions #

Main results #

Implementation notes #

We are only interested in Dedekind domains with Krull dimension 1.

References #

Tags #

dedekind domain, dedekind ring, adic valuation

Adic valuations on the Dedekind domain R #

The additive v-adic valuation of r ∈ R is the exponent of v in the factorization of the ideal (r), if r is nonzero, or infinity, if r = 0. intValuationDef is the corresponding multiplicative valuation.

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    The v-adic valuation of r ∈ R is less than 1 if and only if v divides the ideal (r).

    The v-adic valuation of r ∈ R is less than Multiplicative.ofAdd (-n) if and only if vⁿ divides the ideal (r).

    theorem IsDedekindDomain.HeightOneSpectrum.IntValuation.le_max_iff_min_le {a : } {b : } {c : } :
    Multiplicative.ofAdd (-c) max (Multiplicative.ofAdd (-a)) (Multiplicative.ofAdd (-b)) min a b c

    The v-adic valuation on R.

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      There exists π ∈ R with v-adic valuation Multiplicative.ofAdd (-1).

      Adic valuations on the field of fractions K #

      The v-adic valuation of x ∈ K is the valuation of r divided by the valuation of s, where r and s are chosen so that x = r/s.

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        The v-adic valuation on R is bounded above by 1.

        The v-adic valuation of r ∈ R is less than 1 if and only if v divides the ideal (r).

        There exists π ∈ K with v-adic valuation Multiplicative.ofAdd (-1).

        Uniformizers are nonzero.

        Completions with respect to adic valuations #

        Given a Dedekind domain R with field of fractions K and a maximal ideal v of R, we define the completion of K with respect to its v-adic valuation, denoted v.adicCompletion, and its ring of integers, denoted v.adicCompletionIntegers.

        The completion of K with respect to its v-adic valuation.

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          @[simp]
          theorem IsDedekindDomain.HeightOneSpectrum.coe_smul_adicCompletion (R : Type u_1) [CommRing R] [IsDomain R] [IsDedekindDomain R] (K : Type u_2) [Field K] [Algebra R K] [IsFractionRing R K] (v : IsDedekindDomain.HeightOneSpectrum R) (r : R) (x : K) :
          K (r x) = r K x