Documentation

Mathlib.RingTheory.Localization.AtPrime.Basic

Localizations of commutative rings at the complement of a prime ideal #

Main definitions #

Main results #

Implementation notes #

See RingTheory.Localization.Basic for a design overview.

Tags #

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

@[reducible, inline]
abbrev IsLocalization.AtPrime {R : Type u_1} [CommSemiring R] (S : Type u_2) [CommSemiring S] [Algebra R S] (P : Ideal R) [hp : P.IsPrime] :

Given a prime ideal P, the typeclass IsLocalization.AtPrime S P states that S is isomorphic to the localization of R at the complement of P.

Equations
    Instances For
      @[reducible, inline]
      abbrev Localization.AtPrime {R : Type u_1} [CommSemiring R] (P : Ideal R) [hp : P.IsPrime] :
      Type u_1

      Given a prime ideal P, Localization.AtPrime P is a localization of R at the complement of P, as a quotient type.

      Equations
        Instances For

          The localization of an integral domain at the complement of a prime ideal is an integral domain.

          The localization of R at the complement of a prime ideal is a local ring.

          The prime ideals in the localization of a commutative ring at a prime ideal I are in order-preserving bijection with the prime ideals contained in I.

          Equations
            Instances For
              @[simp]
              theorem IsLocalization.AtPrime.coe_orderIsoOfPrime_symm_apply_coe {R : Type u_1} [CommSemiring R] (S : Type u_2) [CommSemiring S] [Algebra R S] (I : Ideal R) [hI : I.IsPrime] [IsLocalization.AtPrime S I] (a✝ : { p : Ideal R // p.IsPrime p I }) :
              ((RelIso.symm (orderIsoOfPrime S I)) a✝) = ⋂ (s : Submodule S S), ⋂ (_ : ((OrderIso.setCongr (fun (p : Ideal R) => p.IsPrime Disjoint I.primeCompl p) (fun (p : Ideal R) => p.IsPrime p I) ).symm a✝) (algebraMap R S) ⁻¹' s), s
              @[simp]
              theorem IsLocalization.AtPrime.coe_orderIsoOfPrime_apply_coe {R : Type u_1} [CommSemiring R] (S : Type u_2) [CommSemiring S] [Algebra R S] (I : Ideal R) [hI : I.IsPrime] [IsLocalization.AtPrime S I] (a✝ : { p : Ideal S // p.IsPrime }) :
              ((orderIsoOfPrime S I) a✝) = (algebraMap R S) ⁻¹' a✝
              def IsLocalization.AtPrime.primeSpectrumOrderIso {R : Type u_1} [CommSemiring R] (S : Type u_2) [CommSemiring S] [Algebra R S] (I : Ideal R) [hI : I.IsPrime] [IsLocalization.AtPrime S I] :
              PrimeSpectrum S ≃o (Set.Iic { asIdeal := I, isPrime := hI })

              The prime spectrum of the localization of a commutative ring R at a prime ideal I are in order-preserving bijection with the interval (-∞, I] in the prime spectrum of R.

              Equations
                Instances For
                  @[simp]
                  theorem IsLocalization.AtPrime.coe_primeSpectrumOrderIso_symm_apply_asIdeal {R : Type u_1} [CommSemiring R] (S : Type u_2) [CommSemiring S] [Algebra R S] (I : Ideal R) [hI : I.IsPrime] [IsLocalization.AtPrime S I] (a✝ : (Set.Iic { asIdeal := I, isPrime := hI })) :
                  ((RelIso.symm (primeSpectrumOrderIso S I)) a✝).asIdeal = ⋂ (s : Submodule S S), ⋂ (_ : ((OrderIso.setCongr (fun (p : Ideal R) => p.IsPrime Disjoint I.primeCompl p) (fun (p : Ideal R) => p.IsPrime p I) ).symm (↑a✝).asIdeal, ) (algebraMap R S) ⁻¹' s), s
                  theorem IsLocalization.AtPrime.isUnit_to_map_iff {R : Type u_1} [CommSemiring R] (S : Type u_2) [CommSemiring S] [Algebra R S] (I : Ideal R) [hI : I.IsPrime] [IsLocalization.AtPrime S I] (x : R) :
                  theorem IsLocalization.AtPrime.isUnit_mk'_iff {R : Type u_1} [CommSemiring R] (S : Type u_2) [CommSemiring S] [Algebra R S] (I : Ideal R) [hI : I.IsPrime] [IsLocalization.AtPrime S I] (x : R) (y : I.primeCompl) :
                  theorem IsLocalization.AtPrime.mk'_mem_maximal_iff {R : Type u_1} [CommSemiring R] (S : Type u_2) [CommSemiring S] [Algebra R S] (I : Ideal R) [hI : I.IsPrime] [IsLocalization.AtPrime S I] (x : R) (y : I.primeCompl) (h : IsLocalRing S := ) :

                  The unique maximal ideal of the localization at I.primeCompl lies over the ideal I.

                  The image of I in the localization at I.primeCompl is a maximal ideal, and in particular it is the unique maximal ideal given by the local ring structure AtPrime.isLocalRing

                  noncomputable def Localization.localRingHom {R : Type u_1} [CommSemiring R] {P : Type u_3} [CommSemiring P] (I : Ideal R) [hI : I.IsPrime] (J : Ideal P) [J.IsPrime] (f : R →+* P) (hIJ : I = Ideal.comap f J) :

                  For a ring hom f : R →+* S and a prime ideal J in S, the induced ring hom from the localization of R at J.comap f to the localization of S at J.

                  To make this definition more flexible, we allow any ideal I of R as input, together with a proof that I = J.comap f. This can be useful when I is not definitionally equal to J.comap f.

                  Equations
                    Instances For
                      @[simp]
                      theorem Localization.localRingHom_to_map {R : Type u_1} [CommSemiring R] {P : Type u_3} [CommSemiring P] (I : Ideal R) [hI : I.IsPrime] (J : Ideal P) [J.IsPrime] (f : R →+* P) (hIJ : I = Ideal.comap f J) (x : R) :
                      @[simp]
                      theorem Localization.localRingHom_mk' {R : Type u_1} [CommSemiring R] {P : Type u_3} [CommSemiring P] (I : Ideal R) [hI : I.IsPrime] (J : Ideal P) [J.IsPrime] (f : R →+* P) (hIJ : I = Ideal.comap f J) (x : R) (y : I.primeCompl) :
                      instance Localization.isLocalHom_localRingHom {R : Type u_1} [CommSemiring R] {P : Type u_3} [CommSemiring P] (I : Ideal R) [hI : I.IsPrime] (J : Ideal P) [hJ : J.IsPrime] (f : R →+* P) (hIJ : I = Ideal.comap f J) :
                      theorem Localization.localRingHom_unique {R : Type u_1} [CommSemiring R] {P : Type u_3} [CommSemiring P] (I : Ideal R) [hI : I.IsPrime] (J : Ideal P) [J.IsPrime] (f : R →+* P) (hIJ : I = Ideal.comap f J) {j : Localization.AtPrime I →+* Localization.AtPrime J} (hj : ∀ (x : R), j ((algebraMap R (Localization.AtPrime I)) x) = (algebraMap P (Localization.AtPrime J)) (f x)) :
                      localRingHom I J f hIJ = j
                      theorem Localization.localRingHom_comp {R : Type u_1} [CommSemiring R] {P : Type u_3} [CommSemiring P] (I : Ideal R) [hI : I.IsPrime] {S : Type u_4} [CommSemiring S] (J : Ideal S) [hJ : J.IsPrime] (K : Ideal P) [hK : K.IsPrime] (f : R →+* S) (hIJ : I = Ideal.comap f J) (g : S →+* P) (hJK : J = Ideal.comap g K) :
                      localRingHom I K (g.comp f) = (localRingHom J K g hJK).comp (localRingHom I J f hIJ)
                      noncomputable def Localization.localAlgHom {R : Type u_1} [CommSemiring R] {S : Type u_2} [CommSemiring S] [Algebra R S] {P : Type u_3} [CommSemiring P] [Algebra R P] (I : Ideal S) [I.IsPrime] (J : Ideal P) [J.IsPrime] (f : S →ₐ[R] P) (hIJ : I = Ideal.comap f J) :

                      For an algebra hom f : S →ₐ[R] P and a prime ideal J in P, the induced ring hom from the localization of R at J ∩ S to the localization of P at J.

                      Equations
                        Instances For
                          @[simp]
                          theorem Localization.localAlgHom_apply {R : Type u_1} [CommSemiring R] {S : Type u_2} [CommSemiring S] [Algebra R S] {P : Type u_3} [CommSemiring P] [Algebra R P] (I : Ideal S) [I.IsPrime] (J : Ideal P) [J.IsPrime] (f : S →ₐ[R] P) (hIJ : I = Ideal.comap f J) (x : Localization.AtPrime I) :
                          (localAlgHom I J f hIJ) x = (localRingHom I J f.toRingHom hIJ) x
                          theorem Localization.localRingHom_bijective_of_saturated_inf_eq_top {R : Type u_1} [CommSemiring R] (S : Type u_2) [CommSemiring S] [Algebra R S] {P : Ideal S} [P.IsPrime] {s : Subalgebra R S} (H : s.saturation (P.primeCompls.toSubmonoid) = ) (p : Ideal s) [p.IsPrime] [P.LiesOver p] :
                          noncomputable instance Localization.AtPrime.instAlgebraOfLiesOver {A : Type u_4} {B : Type u_5} [CommRing A] [CommRing B] [Algebra A B] (p : Ideal A) [p.IsPrime] (P : Ideal B) [P.IsPrime] [P.LiesOver p] :
                          Equations
                            instance Localization.AtPrime.instIsScalarTower {R : Type u_1} [CommSemiring R] {A : Type u_4} {B : Type u_5} [CommRing A] [CommRing B] [Algebra A B] [Algebra R A] [Algebra R B] [IsScalarTower R A B] (p : Ideal A) [p.IsPrime] (P : Ideal B) [P.IsPrime] [P.LiesOver p] :
                            instance Localization.AtPrime.instIsScalarTower_1 {A : Type u_4} {B : Type u_5} {C : Type u_6} [CommRing A] [CommRing B] [CommRing C] [Algebra A B] [Algebra A C] [Algebra B C] [IsScalarTower A B C] (p : Ideal A) [p.IsPrime] (P : Ideal B) [P.IsPrime] [P.LiesOver p] (Q : Ideal C) [Q.IsPrime] [Q.LiesOver P] [Q.LiesOver p] :
                            @[reducible, inline]
                            noncomputable abbrev Localization.AtPrime.mapPiEvalRingHom {ι : Type u_4} {R : ιType u_5} [(i : ι) → CommSemiring (R i)] {i : ι} (I : Ideal (R i)) [I.IsPrime] :

                            Localization.localRingHom specialized to a projection homomorphism from a product ring.

                            Equations
                              Instances For
                                theorem Localization.AtPrime.mapPiEvalRingHom_bijective {ι : Type u_4} {R : ιType u_5} [(i : ι) → CommSemiring (R i)] {i : ι} (I : Ideal (R i)) [I.IsPrime] :
                                theorem Localization.AtPrime.mapPiEvalRingHom_comp_algebraMap {ι : Type u_4} {R : ιType u_5} [(i : ι) → CommSemiring (R i)] {i : ι} (I : Ideal (R i)) [I.IsPrime] :
                                theorem Localization.AtPrime.mapPiEvalRingHom_algebraMap_apply {ι : Type u_4} {R : ιType u_5} [(i : ι) → CommSemiring (R i)] {i : ι} (I : Ideal (R i)) [I.IsPrime] {r : (i : ι) → R i} :
                                theorem Ideal.isPrime_map_of_isLocalizationAtPrime {R : Type u_1} [CommSemiring R] (q : Ideal R) [q.IsPrime] {S : Type u_4} [CommSemiring S] [Algebra R S] [IsLocalization.AtPrime S q] {p : Ideal R} [p.IsPrime] (hpq : p q) :
                                theorem Ideal.under_map_of_isLocalizationAtPrime {R : Type u_1} [CommSemiring R] (q : Ideal R) [q.IsPrime] {S : Type u_4} [CommSemiring S] [Algebra R S] [IsLocalization.AtPrime S q] {p : Ideal R} [p.IsPrime] (hpq : p q) :
                                under R (map (algebraMap R S) p) = p
                                theorem IsLocalization.liesOver_of_isPrime_of_disjoint {R : Type u_1} [CommSemiring R] {S : Type u_4} [CommSemiring S] [Algebra R S] {R' : Type u_5} {S' : Type u_6} (M : Submonoid R) (T : Submonoid S) [CommSemiring R'] [CommSemiring S'] [Algebra R R'] [Algebra S S'] [Algebra R' S'] [Algebra R S'] [IsScalarTower R S S'] [IsScalarTower R R' S'] [IsLocalization M R'] [IsLocalization T S'] (p : Ideal R) {P : Ideal S} [P.IsPrime] [P.LiesOver p] (disj : Disjoint T P) :

                                If R' (resp. S') is the localization of R (resp. S) and P lies over p then the image of P in S' lies over the image of p in R'.

                                instance IsLocalization.AtPrime.isMaximal_map {R : Type u_1} [CommSemiring R] (p : Ideal R) [p.IsPrime] (Rₚ : Type u_4) [CommSemiring Rₚ] [Algebra R Rₚ] [IsLocalization.AtPrime Rₚ p] [IsLocalRing Rₚ] :
                                theorem IsLocalization.AtPrime.comap_map_of_isMaximal {R : Type u_1} [CommSemiring R] (S : Type u_2) [CommSemiring S] [Algebra R S] (p : Ideal R) [p.IsPrime] (Sₚ : Type u_5) [CommSemiring Sₚ] [Algebra S Sₚ] [IsLocalization (Algebra.algebraMapSubmonoid S p.primeCompl) Sₚ] (P : Ideal S) [P.IsMaximal] [P.LiesOver p] :
                                Ideal.comap (algebraMap S Sₚ) (Ideal.map (algebraMap S Sₚ) P) = P
                                noncomputable def IsLocalization.AtPrime.equivQuotMaximalIdeal {R : Type u_7} [CommRing R] (p : Ideal R) [p.IsMaximal] (Rₚ : Type u_8) [CommRing Rₚ] [Algebra R Rₚ] [IsLocalization.AtPrime Rₚ p] [IsLocalRing Rₚ] :

                                The isomorphism R ⧸ p ≃+* Rₚ ⧸ maximalIdeal Rₚ, where Rₚ satisfies IsLocalization.AtPrime Rₚ p. In particular, localization preserves the residue field.

                                Equations
                                  Instances For
                                    @[deprecated IsLocalization.AtPrime.equivQuotMaximalIdeal (since := "2025-11-13")]
                                    def equivQuotMaximalIdealOfIsLocalization {R : Type u_7} [CommRing R] (p : Ideal R) [p.IsMaximal] (Rₚ : Type u_8) [CommRing Rₚ] [Algebra R Rₚ] [IsLocalization.AtPrime Rₚ p] [IsLocalRing Rₚ] :

                                    Alias of IsLocalization.AtPrime.equivQuotMaximalIdeal.


                                    The isomorphism R ⧸ p ≃+* Rₚ ⧸ maximalIdeal Rₚ, where Rₚ satisfies IsLocalization.AtPrime Rₚ p. In particular, localization preserves the residue field.

                                    Equations
                                      Instances For
                                        theorem IsLocalization.AtPrime.comap_map_eq_map {S : Type u_6} {R : Type u_7} [CommRing R] (p : Ideal R) [p.IsMaximal] {Sₚ : Type u_9} [CommRing S] [Algebra R S] [CommRing Sₚ] [Algebra S Sₚ] [Algebra R Sₚ] [IsLocalization (Algebra.algebraMapSubmonoid S p.primeCompl) Sₚ] [IsScalarTower R S Sₚ] :
                                        noncomputable def IsLocalization.AtPrime.equivQuotientMapMaximalIdeal (S : Type u_6) {R : Type u_7} [CommRing R] (p : Ideal R) [p.IsMaximal] (Rₚ : Type u_8) [CommRing Rₚ] [Algebra R Rₚ] [IsLocalization.AtPrime Rₚ p] [IsLocalRing Rₚ] (Sₚ : Type u_9) [CommRing S] [Algebra R S] [CommRing Sₚ] [Algebra S Sₚ] [Algebra R Sₚ] [Algebra Rₚ Sₚ] [IsLocalization (Algebra.algebraMapSubmonoid S p.primeCompl) Sₚ] [IsScalarTower R S Sₚ] [IsScalarTower R Rₚ Sₚ] [p.IsMaximal] :

                                        The isomorphism S ⧸ pS ≃+* Sₚ ⧸ p·Sₚ, where Sₚ is the localization of S at the (image) of the complement of p

                                        Equations
                                          Instances For