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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    Nonzero elements have nonzero adic valuation.

    Nonzero divisors have nonzero valuation.

    Nonzero divisors have valuation greater than zero.

    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).

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

    The v-adic valuation of 0 : R equals 0.

    The v-adic valuation of 1 : R equals 1.

    The v-adic valuation of a product equals the product of the valuations.

    The v-adic valuation of a sum is bounded above by the maximum of the valuations.

    The v-adic valuation on R.

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

      The I-adic valuation of a generator of I equals (-1 : ℤₘ₀)

      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 of r/s ∈ K is the valuation of r divided by the valuation of s.

        The v-adic valuation on K extends the v-adic valuation on R.

        theorem IsDedekindDomain.HeightOneSpectrum.valuation_le_one {R : Type u_1} [CommRing R] [IsDedekindDomain R] {K : Type u_2} [Field K] [Algebra R K] [IsFractionRing R K] (v : HeightOneSpectrum R) (r : R) :
        (valuation K v) r 1

        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).

        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.

        K as a valued field with the v-adic valuation.

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

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            theorem IsDedekindDomain.HeightOneSpectrum.coe_smul_adicCompletion (R : Type u_1) [CommRing R] [IsDedekindDomain R] (K : Type u_2) {S : Type u_3} [Field K] [CommSemiring S] [Algebra R K] [IsFractionRing R K] (v : HeightOneSpectrum R) [Algebra S K] (r : S) (x : K) :
            ↑(r x) = r x
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            • One or more equations did not get rendered due to their size.

            The valuation on the completion agrees with the global valuation on elements of the integer ring.

            The valuation on the completion agrees with the global valuation on elements of the field.

            A global integer is in the local integers.

            @[simp]