Documentation

Mathlib.RingTheory.Localization.Ideal

Ideals in localizations of commutative rings #

Implementation notes #

See Mathlib/RingTheory/Localization/Basic.lean for a design overview.

Tags #

localization, ring localization, commutative ring localization, characteristic predicate, commutative ring, field of fractions

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theorem IsLocalization.mem_map_algebraMap_iff {R : Type u_1} [CommSemiring R] (M : Submonoid R) (S : Type u_2) [CommSemiring S] [Algebra R S] [IsLocalization M S] {I : Ideal R} {z : S} :
z ∈ Ideal.map (algebraMap R S) I ↔ ∃ (x : ↥I × ↥M), z * (algebraMap R S) ↑x.2 = (algebraMap R S) ↑x.1
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theorem IsLocalization.map_comap {R : Type u_1} [CommSemiring R] (M : Submonoid R) (S : Type u_2) [CommSemiring S] [Algebra R S] [IsLocalization M S] (J : Ideal S) :
Ideal.map (algebraMap R S) (Ideal.comap (algebraMap R S) J) = J
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theorem IsLocalization.comap_map_of_isPrime_disjoint {R : Type u_1} [CommSemiring R] (M : Submonoid R) (S : Type u_2) [CommSemiring S] [Algebra R S] [IsLocalization M S] (I : Ideal R) (hI : I.IsPrime) (hM : Disjoint ↑M ↑I) :
Ideal.comap (algebraMap R S) (Ideal.map (algebraMap R S) I) = I
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def IsLocalization.orderEmbedding {R : Type u_1} [CommSemiring R] (M : Submonoid R) (S : Type u_2) [CommSemiring S] [Algebra R S] [IsLocalization M S] :
Ideal S ↪o Ideal R

If S is the localization of R at a submonoid, the ordering of ideals of S is embedded in the ordering of ideals of R.

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    theorem IsLocalization.isPrime_iff_isPrime_disjoint {R : Type u_1} [CommSemiring R] (M : Submonoid R) (S : Type u_2) [CommSemiring S] [Algebra R S] [IsLocalization M S] (J : Ideal S) :
    J.IsPrime ↔ (Ideal.comap (algebraMap R S) J).IsPrime ∧ Disjoint ↑M ↑(Ideal.comap (algebraMap R S) J)

    If R is a ring, then prime ideals in the localization at M correspond to prime ideals in the original ring R that are disjoint from M. This lemma gives the particular case for an ideal and its comap, see le_rel_iso_of_prime for the more general relation isomorphism

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    theorem IsLocalization.isPrime_of_isPrime_disjoint {R : Type u_1} [CommSemiring R] (M : Submonoid R) (S : Type u_2) [CommSemiring S] [Algebra R S] [IsLocalization M S] (I : Ideal R) (hp : I.IsPrime) (hd : Disjoint ↑M ↑I) :
    (Ideal.map (algebraMap R S) I).IsPrime

    If R is a ring, then prime ideals in the localization at M correspond to prime ideals in the original ring R that are disjoint from M. This lemma gives the particular case for an ideal and its map, see le_rel_iso_of_prime for the more general relation isomorphism, and the reverse implication

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    def IsLocalization.orderIsoOfPrime {R : Type u_1} [CommSemiring R] (M : Submonoid R) (S : Type u_2) [CommSemiring S] [Algebra R S] [IsLocalization M S] :
    { p : Ideal S // p.IsPrime } ≃o { p : Ideal R // p.IsPrime ∧ Disjoint ↑M ↑p }

    If R is a ring, then prime ideals in the localization at M correspond to prime ideals in the original ring R that are disjoint from M

    Equations
    • One or more equations did not get rendered due to their size.
    Instances For
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      theorem IsLocalization.surjective_quotientMap_of_maximal_of_localization {R : Type u_1} [CommRing R] (M : Submonoid R) (S : Type u_2) [CommRing S] [Algebra R S] [IsLocalization M S] {I : Ideal S} [I.IsPrime] {J : Ideal R} {H : J ≤ Ideal.comap (algebraMap R S) I} (hI : (Ideal.comap (algebraMap R S) I).IsMaximal) :
      Function.Surjective ⇑(Ideal.quotientMap I (algebraMap R S) H)

      quotientMap applied to maximal ideals of a localization is surjective. The quotient by a maximal ideal is a field, so inverses to elements already exist, and the localization necessarily maps the equivalence class of the inverse in the localization

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      theorem IsLocalization.bot_lt_comap_prime {R : Type u_1} [CommRing R] (M : Submonoid R) (S : Type u_2) [CommRing S] [Algebra R S] [IsLocalization M S] [IsDomain R] (hM : M ≤ nonZeroDivisors R) (p : Ideal S) [hpp : p.IsPrime] (hp0 : p ≠ ⊥) :
      ⊥ < Ideal.comap (algebraMap R S) p