Documentation

Mathlib.NumberTheory.NumberField.Completion.FinitePlace

Finite places of number fields #

This file defines finite places of a number field K as absolute values coming from an embedding into a completion of K associated to a non-zero prime ideal of ๐“ž K.

Many of the results in this file are expressed in the generality of: R is a Dedekind domain with field of fractions K such that Module.Finite โ„ค R and Module.Free โ„ค R. If K is a number field, then this characterises R as being isomorphic to ๐“ž K without explicitly requiring ๐“ž K. This is so that โ„ค and ๐“ž โ„š can be used interchangeably.

Main Definitions and Results #

Tags #

number field, places, finite places

In this section we assume further that Module.Finite โ„ค R and Module.Free โ„ค R. This characterises R as being isomorphic to ๐“ž K without explicitly requiring that type. As a result, if F = โ„š, then we can use โ„ค and ๐“ž โ„š interchangeably.

The norm of a maximal ideal as an element of โ„โ‰ฅ0 is > 1

The norm of a maximal ideal as an element of โ„โ‰ฅ0 is โ‰  0

The v-adic absolute value on K defined as the norm of v raised to negative v-adic valuation

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    The v-adic absolute value satisfies the ultrametric inequality.

    The v-adic absolute value of a natural number is โ‰ค 1.

    The v-adic absolute value of an integer is โ‰ค 1.

    @[deprecated NumberField.HeightOneSpectrum.one_lt_absNorm (since := "2026-03-11")]

    Alias of NumberField.HeightOneSpectrum.one_lt_absNorm.


    The norm of a maximal ideal is > 1

    @[deprecated NumberField.HeightOneSpectrum.one_lt_absNorm (since := "2026-03-11")]

    Alias of NumberField.HeightOneSpectrum.one_lt_absNorm.


    The norm of a maximal ideal is > 1

    @[deprecated NumberField.HeightOneSpectrum.one_lt_absNorm_nnreal (since := "2026-03-11")]

    Alias of NumberField.HeightOneSpectrum.one_lt_absNorm_nnreal.


    The norm of a maximal ideal as an element of โ„โ‰ฅ0 is > 1

    @[deprecated NumberField.HeightOneSpectrum.one_lt_absNorm_nnreal (since := "2026-03-11")]

    Alias of NumberField.HeightOneSpectrum.one_lt_absNorm_nnreal.


    The norm of a maximal ideal as an element of โ„โ‰ฅ0 is > 1

    @[deprecated NumberField.HeightOneSpectrum.absNorm_ne_zero (since := "2026-03-11")]

    Alias of NumberField.HeightOneSpectrum.absNorm_ne_zero.


    The norm of a maximal ideal as an element of โ„โ‰ฅ0 is โ‰  0

    @[deprecated NumberField.HeightOneSpectrum.absNorm_ne_zero (since := "2026-03-11")]

    Alias of NumberField.HeightOneSpectrum.absNorm_ne_zero.


    The norm of a maximal ideal as an element of โ„โ‰ฅ0 is โ‰  0

    @[deprecated NumberField.HeightOneSpectrum.adicAbv (since := "2026-03-11")]

    Alias of NumberField.HeightOneSpectrum.adicAbv.


    The v-adic absolute value on K defined as the norm of v raised to negative v-adic valuation

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      @[deprecated NumberField.HeightOneSpectrum.adicAbv (since := "2026-03-11")]

      Alias of NumberField.HeightOneSpectrum.adicAbv.


      The v-adic absolute value on K defined as the norm of v raised to negative v-adic valuation

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        @[deprecated NumberField.HeightOneSpectrum.isNonarchimedean_adicAbv (since := "2026-03-11")]

        Alias of NumberField.HeightOneSpectrum.isNonarchimedean_adicAbv.


        The v-adic absolute value is nonarchimedean

        @[deprecated NumberField.HeightOneSpectrum.isNonarchimedean_adicAbv (since := "2026-03-11")]

        Alias of NumberField.HeightOneSpectrum.isNonarchimedean_adicAbv.


        The v-adic absolute value is nonarchimedean

        @[deprecated NumberField.HeightOneSpectrum.adicAbv_add_le_max (since := "2026-03-11")]

        Alias of NumberField.HeightOneSpectrum.adicAbv_add_le_max.


        The v-adic absolute value satisfies the ultrametric inequality.

        @[deprecated NumberField.HeightOneSpectrum.adicAbv_add_le_max (since := "2026-03-11")]

        Alias of NumberField.HeightOneSpectrum.adicAbv_add_le_max.


        The v-adic absolute value satisfies the ultrametric inequality.

        @[deprecated NumberField.HeightOneSpectrum.adicAbv_natCast_le_one (since := "2026-03-11")]

        Alias of NumberField.HeightOneSpectrum.adicAbv_natCast_le_one.


        The v-adic absolute value of a natural number is โ‰ค 1.

        @[deprecated NumberField.HeightOneSpectrum.adicAbv_natCast_le_one (since := "2026-03-11")]

        Alias of NumberField.HeightOneSpectrum.adicAbv_natCast_le_one.


        The v-adic absolute value of a natural number is โ‰ค 1.

        @[deprecated NumberField.HeightOneSpectrum.adicAbv_intCast_le_one (since := "2026-03-11")]

        Alias of NumberField.HeightOneSpectrum.adicAbv_intCast_le_one.


        The v-adic absolute value of an integer is โ‰ค 1.

        @[deprecated NumberField.HeightOneSpectrum.adicAbv_intCast_le_one (since := "2026-03-11")]

        Alias of NumberField.HeightOneSpectrum.adicAbv_intCast_le_one.


        The v-adic absolute value of an integer is โ‰ค 1.

        The norm of an element in the v-adic completion of K. See FinitePlace.norm_embedding for the equality involving โ€–embedding v xโ€– on the LHS.

        The norm of the image after the embedding associated to v is equal to the v-adic absolute value.

        The norm of the image after the embedding associated to v is equal to the norm of v raised to the power of the v-adic valuation.

        The norm of the image after the embedding associated to v is equal to the norm of v raised to the power of the v-adic valuation for integers.

        @[deprecated NumberField.FinitePlace.norm_embedding' (since := "2026-03-05")]

        Alias of NumberField.FinitePlace.norm_embedding'.


        The norm of the image after the embedding associated to v is equal to the norm of v raised to the power of the v-adic valuation.

        @[deprecated NumberField.FinitePlace.norm_embedding_int (since := "2026-03-05")]

        Alias of NumberField.FinitePlace.norm_embedding_int.


        The norm of the image after the embedding associated to v is equal to the norm of v raised to the power of the v-adic valuation for integers.

        The v-adic norm of an integer is at most 1.

        The v-adic norm of an integer is 1 if and only if it is not in the ideal.

        The v-adic norm of an integer is less than 1 if and only if it is in the ideal.

        A finite place of a number field K is a place associated to an embedding into a completion with respect to a maximal ideal.

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        • One or more equations did not get rendered due to their size.
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          Return the finite place defined by a maximal ideal v.

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            A predicate singling out finite places among the absolute values on a number field K.

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              theorem NumberField.isFinitePlace_iff {K : Type u_1} [Field K] [NumberField K] (v : AbsoluteValue K โ„) :
              IsFinitePlace v โ†” โˆƒ (w : FinitePlace K), โ†‘w = v
              @[implicit_reducible]
              Equations
              theorem NumberField.FinitePlace.coe_apply {K : Type u_1} [Field K] [NumberField K] (v : FinitePlace K) (x : K) :
              v x = โ†‘v x

              For a finite place w, return a maximal ideal v such that w = finite_place v .

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                theorem NumberField.FinitePlace.pos_iff {K : Type u_1} [Field K] [NumberField K] {w : FinitePlace K} {x : K} :
                0 < w x โ†” x โ‰  0
                @[simp]
                theorem NumberField.FinitePlace.mk_eq_iff {K : Type u_1} [Field K] [NumberField K] {vโ‚ vโ‚‚ : IsDedekindDomain.HeightOneSpectrum (RingOfIntegers K)} :
                mk vโ‚ = mk vโ‚‚ โ†” vโ‚ = vโ‚‚

                The equivalence between finite places and maximal ideals.

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                  theorem NumberField.FinitePlace.maximalIdeal_inj {K : Type u_1} [Field K] [NumberField K] (wโ‚ wโ‚‚ : FinitePlace K) :
                  wโ‚.maximalIdeal = wโ‚‚.maximalIdeal โ†” wโ‚ = wโ‚‚
                  @[deprecated NumberField.FinitePlace.hasFiniteMulSupport_int (since := "2026-03-03")]
                  theorem NumberField.FinitePlace.mulSupport_finite_int {K : Type u_1} [Field K] [NumberField K] {x : RingOfIntegers K} (h_x_nezero : x โ‰  0) :
                  Function.HasFiniteMulSupport fun (w : FinitePlace K) => w โ†‘x

                  Alias of NumberField.FinitePlace.hasFiniteMulSupport_int.

                  theorem NumberField.FinitePlace.hasFiniteMulSupport {K : Type u_1} [Field K] [NumberField K] {x : K} (h_x_nezero : x โ‰  0) :
                  @[deprecated NumberField.FinitePlace.hasFiniteMulSupport (since := "2026-03-03")]
                  theorem NumberField.FinitePlace.mulSupport_finite {K : Type u_1} [Field K] [NumberField K] {x : K} (h_x_nezero : x โ‰  0) :

                  Alias of NumberField.FinitePlace.hasFiniteMulSupport.

                  theorem NumberField.FinitePlace.add_le {K : Type u_1} [Field K] [NumberField K] (v : FinitePlace K) (x y : K) :
                  v (x + y) โ‰ค max (v x) (v y)
                  @[deprecated NumberField.HeightOneSpectrum.embedding_mul_absNorm (since := "2026-03-11")]

                  Alias of NumberField.HeightOneSpectrum.embedding_mul_absNorm.