Localizations of commutative monoids #
Localizing a commutative ring at one of its submonoids does not rely on the ring's addition, so we can generalize localizations to commutative monoids.
We characterize the localization of a commutative monoid M at a submonoid S up to
isomorphism; that is, a commutative monoid N is the localization of M at S iff we can find a
monoid homomorphism f : M →* N satisfying 3 properties:
- For all
y ∈ S,f yis a unit; - For all
z : N, there exists(x, y) : M × Ssuch thatz * f y = f x; - For all
x, y : Msuch thatf x = f y, there existsc ∈ Ssuch thatx * c = y * c. (The converse is a consequence of 1.)
Given such a localization map f : M →* N, we can define the surjection
Submonoid.LocalizationMap.mk' sending (x, y) : M × S to f x * (f y)⁻¹, and
Submonoid.LocalizationMap.lift, the homomorphism from N induced by a homomorphism from M which
maps elements of S to invertible elements of the codomain. Similarly, given commutative monoids
P, Q, a submonoid T of P and a localization map for T from P to Q, then a homomorphism
g : M →* P such that g(S) ⊆ T induces a homomorphism of localizations, LocalizationMap.map,
from N to Q.
We also define the quotient of M × S by the unique congruence relation (equivalence relation
preserving a binary operation) r such that for any other congruence relation s on M × S
satisfying '∀ y ∈ S, (1, 1) ∼ (y, y) under s', we have that (x₁, y₁) ∼ (x₂, y₂) by s
whenever (x₁, y₁) ∼ (x₂, y₂) by r. We show this relation is equivalent to the standard
localization relation.
This defines the localization as a quotient type, Localization, but the majority of
subsequent lemmas in the file are given in terms of localizations up to isomorphism, using maps
which satisfy the characteristic predicate.
The Grothendieck group construction corresponds to localizing at the top submonoid, namely making every element invertible.
Implementation notes #
In maths it is natural to reason up to isomorphism, but in Lean we cannot naturally rewrite one
structure with an isomorphic one; one way around this is to isolate a predicate characterizing
a structure up to isomorphism, and reason about things that satisfy the predicate.
The infimum form of the localization congruence relation is chosen as 'canonical' here, since it shortens some proofs.
To reason about the localization as a quotient type, use mk_eq_monoidOf_mk' and associated
lemmas. These show the quotient map mk : M → S → Localization S equals the
surjection LocalizationMap.mk' induced by the map
Localization.monoidOf : Submonoid.LocalizationMap S (Localization S) (where of establishes the
localization as a quotient type satisfies the characteristic predicate). The lemma
mk_eq_monoidOf_mk' hence gives you access to the results in the rest of the file, which are about
the LocalizationMap.mk' induced by any localization map.
TODO #
- Show that the localization at the top monoid is a group.
- Generalise to (nonempty) subsemigroups.
- If we acquire more bundlings, we can make
Localization.mkOrderEmbeddingbe an ordered monoid embedding.
Tags #
localization, monoid localization, quotient monoid, congruence relation, characteristic predicate, commutative monoid, grothendieck group
The type of AddMonoid homomorphisms satisfying the characteristic predicate: if f : M →+ N
satisfies this predicate, then N is isomorphic to the localization of M at S.
- toFun : M → N
- map_add' (x y : M) : (↑self.toAddMonoidHom).toFun (x + y) = (↑self.toAddMonoidHom).toFun x + (↑self.toAddMonoidHom).toFun y
- map_add_units' (y : ↥S) : IsAddUnit ((↑self.toAddMonoidHom).toFun ↑y)
- surj' (z : N) : ∃ (x : M × ↥S), z + (↑self.toAddMonoidHom).toFun ↑x.2 = (↑self.toAddMonoidHom).toFun x.1
- exists_of_eq (x y : M) : (↑self.toAddMonoidHom).toFun x = (↑self.toAddMonoidHom).toFun y → ∃ (c : ↥S), ↑c + x = ↑c + y
Instances For
The type of monoid homomorphisms satisfying the characteristic predicate: if f : M →* N
satisfies this predicate, then N is isomorphic to the localization of M at S.
- toFun : M → N
- map_mul' (x y : M) : (↑self.toMonoidHom).toFun (x * y) = (↑self.toMonoidHom).toFun x * (↑self.toMonoidHom).toFun y
- map_units' (y : ↥S) : IsUnit ((↑self.toMonoidHom).toFun ↑y)
- surj' (z : N) : ∃ (x : M × ↥S), z * (↑self.toMonoidHom).toFun ↑x.2 = (↑self.toMonoidHom).toFun x.1
- exists_of_eq (x y : M) : (↑self.toMonoidHom).toFun x = (↑self.toMonoidHom).toFun y → ∃ (c : ↥S), ↑c * x = ↑c * y
Instances For
The congruence relation on M × S, M a CommMonoid and S a submonoid of M, whose
quotient is the localization of M at S, defined as the unique congruence relation on
M × S such that for any other congruence relation s on M × S where for all y ∈ S,
(1, 1) ∼ (y, y) under s, we have that (x₁, y₁) ∼ (x₂, y₂) by r implies
(x₁, y₁) ∼ (x₂, y₂) by s.
Instances For
The congruence relation on M × S, M an AddCommMonoid and S an AddSubmonoid of M,
whose quotient is the localization of M at S, defined as the unique congruence relation on
M × S such that for any other congruence relation s on M × S where for all y ∈ S,
(0, 0) ∼ (y, y) under s, we have that (x₁, y₁) ∼ (x₂, y₂) by r implies
(x₁, y₁) ∼ (x₂, y₂) by s.
Instances For
An alternate form of the congruence relation on M × S, M a CommMonoid and S a
submonoid of M, whose quotient is the localization of M at S.
Equations
Instances For
An alternate form of the congruence relation on M × S, M a CommMonoid and S a
submonoid of M, whose quotient is the localization of M at S.
Equations
Instances For
The congruence relation used to localize a CommMonoid at a submonoid can be expressed
equivalently as an infimum (see Localization.r) or explicitly
(see Localization.r').
The additive congruence relation used to localize an AddCommMonoid at a submonoid can be
expressed equivalently as an infimum (see AddLocalization.r) or explicitly
(see AddLocalization.r').
The localization of a CommMonoid at one of its submonoids (as a quotient type).
Equations
- Localization S = OreLocalization S M
Instances For
The localization of an AddCommMonoid at one of its submonoids (as a quotient type).
Equations
Instances For
Given a CommMonoid M and submonoid S, mk sends x : M, y ∈ S to the equivalence
class of (x, y) in the localization of M at S.
Equations
- Localization.mk x y = x /ₒ y
Instances For
Given an AddCommMonoid M and submonoid S, mk sends x : M, y ∈ S to
the equivalence class of (x, y) in the localization of M at S.
Equations
- AddLocalization.mk x y = x -ₒ y
Instances For
Dependent recursion principle for Localizations: given elements f a b : p (mk a b)
for all a b, such that r S (a, b) (c, d) implies f a b = f c d (with the correct coercions),
then f is defined on the whole Localization S.
Equations
- Localization.rec f H x = Quot.rec (fun (y : M × ↥S) => ⋯ ▸ f y.1 y.2) ⋯ x
Instances For
Dependent recursion principle for AddLocalizations: given elements f a b : p (mk a b)
for all a b, such that r S (a, b) (c, d) implies f a b = f c d (with the correct coercions),
then f is defined on the whole AddLocalization S.
Equations
- AddLocalization.rec f H x = Quot.rec (fun (y : M × ↥S) => ⋯ ▸ f y.1 y.2) ⋯ x
Instances For
Copy of Quotient.recOnSubsingleton₂ for Localization
Equations
- One or more equations did not get rendered due to their size.
Instances For
Copy of Quotient.recOnSubsingleton₂ for AddLocalization
Equations
- One or more equations did not get rendered due to their size.
Instances For
Non-dependent recursion principle for localizations: given elements f a b : p
for all a b, such that r S (a, b) (c, d) implies f a b = f c d,
then f is defined on the whole Localization S.
Equations
- x.liftOn f H = Localization.rec f ⋯ x
Instances For
Non-dependent recursion principle for AddLocalizations: given elements f a b : p
for all a b, such that r S (a, b) (c, d) implies f a b = f c d,
then f is defined on the whole Localization S.
Equations
- x.liftOn f H = AddLocalization.rec f ⋯ x
Instances For
Non-dependent recursion principle for localizations: given elements f x y : p
for all x and y, such that r S x x' and r S y y' implies f x y = f x' y',
then f is defined on the whole Localization S.
Instances For
Non-dependent recursion principle for localizations: given elements f x y : p
for all x and y, such that r S x x' and r S y y' implies f x y = f x' y',
then f is defined on the whole Localization S.
Instances For
Localization.mk as a monoid hom.
Equations
- Localization.mkHom = { toFun := fun (x : M × ↥S) => Localization.mk x.1 x.2, map_one' := ⋯, map_mul' := ⋯ }
Instances For
Localization.mk as a monoid hom.
Equations
- AddLocalization.mkHom = { toFun := fun (x : M × ↥S) => AddLocalization.mk x.1 x.2, map_zero' := ⋯, map_add' := ⋯ }
Instances For
Makes a localization map from a CommMonoid hom satisfying the characteristic predicate.
Equations
- f.toLocalizationMap H1 H2 H3 = { toMonoidHom := f, map_units' := H1, surj' := H2, exists_of_eq := H3 }
Instances For
Makes a localization map from an AddCommMonoid hom satisfying the
characteristic predicate.
Equations
- f.toLocalizationMap H1 H2 H3 = { toAddMonoidHom := f, map_add_units' := H1, surj' := H2, exists_of_eq := H3 }
Instances For
Short for toMonoidHom; used to apply a localization map as a function.
Equations
- f.toMap = f.toMonoidHom
Instances For
Short for toAddMonoidHom; used to apply a localization map as a function.
Equations
- f.toMap = f.toAddMonoidHom
Instances For
Equations
- Submonoid.LocalizationMap.instFunLike = { coe := fun (f : S.LocalizationMap N) => ⇑f.toMonoidHom, coe_injective' := ⋯ }
Equations
- AddSubmonoid.LocalizationMap.instFunLike = { coe := fun (f : S.LocalizationMap N) => ⇑f.toAddMonoidHom, coe_injective' := ⋯ }
Given a localization map f : M →* N, and z w : N, there exist z' w' : M and d : S
such that f z' / f d = z and f w' / f d = w.
Given a localization map f : M →+ N, and z w : N, there exist z' w' : M and d : S
such that f z' - f d = z and f w' - f d = w.
Given a localization map f : M →* N, a section function sending z : N to some
(x, y) : M × S such that f x * (f y)⁻¹ = z.
Equations
- f.sec z = Classical.choose ⋯
Instances For
Given a localization map f : M →+ N, a section function sending z : N
to some (x, y) : M × S such that f x - f y = z.
Equations
- f.sec z = Classical.choose ⋯
Instances For
Given a MonoidHom f : M →* N and Submonoid S ⊆ M such that f(S) ⊆ Nˣ, for all
w, z : N and y ∈ S, we have w * (f y)⁻¹ = z ↔ w = f y * z.
Given an AddMonoidHom f : M →+ N and Submonoid S ⊆ M such that f(S) ⊆ AddUnits N, for all
w, z : N and y ∈ S, we have w - f y = z ↔ w = f y + z.
Given a MonoidHom f : M →* N and Submonoid S ⊆ M such that f(S) ⊆ Nˣ, for all
w, z : N and y ∈ S, we have z = w * (f y)⁻¹ ↔ z * f y = w.
Given an AddMonoidHom f : M →+ N and Submonoid S ⊆ M such that f(S) ⊆ AddUnits N, for all
w, z : N and y ∈ S, we have z = w - f y ↔ z + f y = w.
Given a MonoidHom f : M →* N and Submonoid S ⊆ M such that
f(S) ⊆ Nˣ, for all x₁ x₂ : M and y₁, y₂ ∈ S, we have
f x₁ * (f y₁)⁻¹ = f x₂ * (f y₂)⁻¹ ↔ f (x₁ * y₂) = f (x₂ * y₁).
Given an AddMonoidHom f : M →+ N and Submonoid S ⊆ M such that
f(S) ⊆ AddUnits N, for all x₁ x₂ : M and y₁, y₂ ∈ S, we have
f x₁ - f y₁ = f x₂ - f y₂ ↔ f (x₁ + y₂) = f (x₂ + y₁).
Given a MonoidHom f : M →* N and Submonoid S ⊆ M such that f(S) ⊆ Nˣ, for all
y, z ∈ S, we have (f y)⁻¹ = (f z)⁻¹ → f y = f z.
Given an AddMonoidHom f : M →+ N and Submonoid S ⊆ M such that
f(S) ⊆ AddUnits N, for all y, z ∈ S, we have - (f y) = - (f z) → f y = f z.
Given a MonoidHom f : M →* N and Submonoid S ⊆ M such that f(S) ⊆ Nˣ, for all
y ∈ S, (f y)⁻¹ is unique.
Given an AddMonoidHom f : M →+ N and Submonoid S ⊆ M such that
f(S) ⊆ AddUnits N, for all y ∈ S, - (f y) is unique.
Given a localization map f : M →* N, the surjection sending (x, y) : M × S to
f x * (f y)⁻¹.
Instances For
Given a localization map f : M →+ N, the surjection sending (x, y) : M × S to
f x - f y.
Instances For
Given a localization map f : M →* N for a submonoid S ⊆ M, for all z : N we have that if
x : M, y ∈ S are such that z * f y = f x, then f x * (f y)⁻¹ = z.
Given a localization map f : M →+ N for an AddSubmonoid S ⊆ M, for all z : N
we have that if x : M, y ∈ S are such that z + f y = f x, then f x - f y = z.
Given a Localization map f : M →* N for a Submonoid S ⊆ M, for all x₁ : M and y₁ ∈ S,
if x₂ : M, y₂ ∈ S are such that f x₁ * (f y₁)⁻¹ * f y₂ = f x₂, then there exists c ∈ S
such that x₁ * y₂ * c = x₂ * y₁ * c.
Given a Localization map f : M →+ N for a Submonoid S ⊆ M, for all x₁ : M
and y₁ ∈ S, if x₂ : M, y₂ ∈ S are such that (f x₁ - f y₁) + f y₂ = f x₂, then there exists
c ∈ S such that x₁ + y₂ + c = x₂ + y₁ + c.
Given a Localization map f : M →* N for a Submonoid S ⊆ M and a map of CommMonoids
g : M →* P such that g(S) ⊆ Units P, f x = f y → g x = g y for all x y : M.
Given a Localization map f : M →+ N for an AddSubmonoid S ⊆ M and a map of
AddCommMonoids g : M →+ P such that g(S) ⊆ AddUnits P, f x = f y → g x = g y
for all x y : M.
Given CommMonoids M, P, Localization maps f : M →* N, k : P →* Q for Submonoids
S, T respectively, and g : M →* P such that g(S) ⊆ T, f x = f y implies
k (g x) = k (g y).
Given AddCommMonoids M, P, Localization maps f : M →+ N, k : P →+ Q for AddSubmonoids
S, T respectively, and g : M →+ P such that g(S) ⊆ T, f x = f y
implies k (g x) = k (g y).
Given a Localization map f : M →* N for a Submonoid S ⊆ M and a map of CommMonoids
g : M →* P such that g y is invertible for all y : S, the homomorphism induced from
N to P sending z : N to g x * (g y)⁻¹, where (x, y) : M × S are such that
z = f x * (f y)⁻¹.
Equations
Instances For
Given a localization map f : M →+ N for a submonoid S ⊆ M and a map of
AddCommMonoids g : M →+ P such that g y is invertible for all y : S, the homomorphism
induced from N to P sending z : N to g x - g y, where (x, y) : M × S are such that
z = f x - f y.
Equations
Instances For
Given a Localization map f : M →* N for a Submonoid S ⊆ M and a map of CommMonoids
g : M →* P such that g y is invertible for all y : S, the homomorphism induced from
N to P maps f x * (f y)⁻¹ to g x * (g y)⁻¹ for all x : M, y ∈ S.
Given a Localization map f : M →+ N for an AddSubmonoid S ⊆ M and a map of
AddCommMonoids g : M →+ P such that g y is invertible for all y : S, the homomorphism
induced from N to P maps f x - f y to g x - g y for all x : M, y ∈ S.
Given a Localization map f : M →* N for a Submonoid S ⊆ M and a localization map
g : M →* P for the same submonoid, the homomorphism induced from
N to P maps f x * (f y)⁻¹ to g x * (g y)⁻¹ for all x : M, y ∈ S.
Given a Localization map f : M →+ N for an AddSubmonoid S ⊆ M and a localization map
g : M →+ P for the same submonoid, the homomorphism
induced from N to P maps f x - f y to g x - g y for all x : M, y ∈ S.
Given a Localization map f : M →* N for a Submonoid S ⊆ M, if a CommMonoid map
g : M →* P induces a map f.lift hg : N →* P then for all z : N, v : P, we have
f.lift hg z = v ↔ g x = g y * v, where x : M, y ∈ S are such that z * f y = f x.
Given a Localization map f : M →+ N for an AddSubmonoid S ⊆ M, if an
AddCommMonoid map g : M →+ P induces a map f.lift hg : N →+ P then for all
z : N, v : P, we have f.lift hg z = v ↔ g x = g y + v, where x : M, y ∈ S are such that
z + f y = f x.
Given a Localization map f : M →* N for a Submonoid S ⊆ M, if a CommMonoid map
g : M →* P induces a map f.lift hg : N →* P then for all z : N, v w : P, we have
f.lift hg z * w = v ↔ g x * w = g y * v, where x : M, y ∈ S are such that
z * f y = f x.
Given a Localization map f : M →+ N for an AddSubmonoid S ⊆ M, if an AddCommMonoid map
g : M →+ P induces a map f.lift hg : N →+ P then for all
z : N, v w : P, we have f.lift hg z + w = v ↔ g x + w = g y + v, where x : M, y ∈ S are such
that z + f y = f x.
Given a Localization map f : M →* N for a Submonoid S ⊆ M, if a CommMonoid map
g : M →* P induces a map f.lift hg : N →* P then for all z : N, we have
f.lift hg z * g y = g x, where x : M, y ∈ S are such that z * f y = f x.
Given a Localization map f : M →+ N for an AddSubmonoid S ⊆ M, if an AddCommMonoid
map g : M →+ P induces a map f.lift hg : N →+ P then for all z : N, we have
f.lift hg z + g y = g x, where x : M, y ∈ S are such that z + f y = f x.
Given a Localization map f : M →* N for a Submonoid S ⊆ M, if a CommMonoid map
g : M →* P induces a map f.lift hg : N →* P then for all z : N, we have
g y * f.lift hg z = g x, where x : M, y ∈ S are such that z * f y = f x.
Given a Localization map f : M →+ N for an AddSubmonoid S ⊆ M, if an AddCommMonoid map
g : M →+ P induces a map f.lift hg : N →+ P then for all z : N, we have
g y + f.lift hg z = g x, where x : M, y ∈ S are such that z + f y = f x.
Given Localization maps f : M →* N for a Submonoid S ⊆ M and
k : M →* Q for a Submonoid T ⊆ M, such that S ≤ T, and we have
l : M →* A, the composition of the induced map f.lift for k with
the induced map k.lift for l is equal to the induced map f.lift for l.
Given Localization maps f : M →+ N for a Submonoid S ⊆ M and
k : M →+ Q for a Submonoid T ⊆ M, such that S ≤ T, and we have
l : M →+ A, the composition of the induced map f.lift for k with
the induced map k.lift for l is equal to the induced map f.lift for l
Given two Localization maps f : M →* N, k : M →* P for a Submonoid S ⊆ M, the hom
from P to N induced by f is left inverse to the hom from N to P induced by k.
Given two Localization maps f : M →+ N, k : M →+ P for a Submonoid S ⊆ M, the hom
from P to N induced by f is left inverse to the hom from N to P induced by k.
Given a CommMonoid homomorphism g : M →* P where for Submonoids S ⊆ M, T ⊆ P we have
g(S) ⊆ T, the induced Monoid homomorphism from the Localization of M at S to the
Localization of P at T: if f : M →* N and k : P →* Q are Localization maps for S and
T respectively, we send z : N to k (g x) * (k (g y))⁻¹, where (x, y) : M × S are such
that z = f x * (f y)⁻¹.
Instances For
Given an AddCommMonoid homomorphism g : M →+ P where for AddSubmonoids S ⊆ M, T ⊆ P we
have g(S) ⊆ T, the induced AddMonoid homomorphism from the Localization of M at S to the
Localization of P at T: if f : M →+ N and k : P →+ Q are Localization maps for S and
T respectively, we send z : N to k (g x) - k (g y), where (x, y) : M × S are such
that z = f x - f y.
Instances For
Given Localization maps f : M →* N, k : P →* Q for Submonoids S, T respectively, if a
CommMonoid homomorphism g : M →* P induces a f.map hy k : N →* Q, then for all z : N,
u : Q, we have f.map hy k z = u ↔ k (g x) = k (g y) * u where x : M, y ∈ S are such that
z * f y = f x.
Given Localization maps f : M →+ N, k : P →+ Q for AddSubmonoids S, T respectively, if an
AddCommMonoid homomorphism g : M →+ P induces a f.map hy k : N →+ Q, then for all z : N,
u : Q, we have f.map hy k z = u ↔ k (g x) = k (g y) + u where x : M, y ∈ S are such that
z + f y = f x.
Given Localization maps f : M →* N, k : P →* Q for Submonoids S, T respectively, if a
CommMonoid homomorphism g : M →* P induces a f.map hy k : N →* Q, then for all z : N,
we have f.map hy k z * k (g y) = k (g x) where x : M, y ∈ S are such that
z * f y = f x.
Given Localization maps f : M →+ N, k : P →+ Q for AddSubmonoids S, T respectively, if an
AddCommMonoid homomorphism g : M →+ P induces a f.map hy k : N →+ Q, then for all z : N,
we have f.map hy k z + k (g y) = k (g x) where x : M, y ∈ S are such that
z + f y = f x.
Given Localization maps f : M →* N, k : P →* Q for Submonoids S, T respectively, if a
CommMonoid homomorphism g : M →* P induces a f.map hy k : N →* Q, then for all z : N,
we have k (g y) * f.map hy k z = k (g x) where x : M, y ∈ S are such that
z * f y = f x.
Given Localization maps f : M →+ N, k : P →+ Q for AddSubmonoids S, T respectively if an
AddCommMonoid homomorphism g : M →+ P induces a f.map hy k : N →+ Q, then for all z : N,
we have k (g y) + f.map hy k z = k (g x) where x : M, y ∈ S are such that
z + f y = f x.
If CommMonoid homs g : M →* P, l : P →* A induce maps of localizations, the composition
of the induced maps equals the map of localizations induced by l ∘ g.
If AddCommMonoid homs g : M →+ P, l : P →+ A induce maps of localizations, the composition
of the induced maps equals the map of localizations induced by l ∘ g.
If CommMonoid homs g : M →* P, l : P →* A induce maps of localizations, the composition
of the induced maps equals the map of localizations induced by l ∘ g.
If AddCommMonoid homs g : M →+ P, l : P →+ A induce maps of localizations, the composition
of the induced maps equals the map of localizations induced by l ∘ g.
Given an injective CommMonoid homomorphism g : M →* P, and a submonoid S ⊆ M,
the induced monoid homomorphism from the localization of M at S to the
localization of P at g S, is injective.
Given an injective AddCommMonoid homomorphism g : M →+ P, and a
submonoid S ⊆ M, the induced monoid homomorphism from the localization of M at S
to the localization of P at g S, is injective.
Given a surjective CommMonoid homomorphism g : M →* P, and a submonoid S ⊆ M,
the induced monoid homomorphism from the localization of M at S to the
localization of P at g S, is surjective.
Given a surjective AddCommMonoid homomorphism g : M →+ P, and a
submonoid S ⊆ M, the induced monoid homomorphism from the localization of M at S
to the localization of P at g S, is surjective.
If f : M →* N and k : M →* P are Localization maps for a Submonoid S, we get an
isomorphism of N and P.
Equations
Instances For
If f : M →+ N and k : M →+ R are Localization maps for an AddSubmonoid S, we get an
isomorphism of N and R.
Equations
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If f : M →* N is a Localization map for a Submonoid S and k : N ≃* P is an isomorphism
of CommMonoids, k ∘ f is a Localization map for M at S.
Equations
- f.ofMulEquivOfLocalizations k = (k.toMonoidHom.comp f.toMonoidHom).toLocalizationMap ⋯ ⋯ ⋯
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If f : M →+ N is a Localization map for a Submonoid S and k : N ≃+ P is an isomorphism
of AddCommMonoids, k ∘ f is a Localization map for M at S.
Equations
- f.ofAddEquivOfLocalizations k = (k.toAddMonoidHom.comp f.toAddMonoidHom).toLocalizationMap ⋯ ⋯ ⋯
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Given CommMonoids M, P and Submonoids S ⊆ M, T ⊆ P, if f : M →* N is a Localization
map for S and k : P ≃* M is an isomorphism of CommMonoids such that k(T) = S, f ∘ k
is a Localization map for T.
Equations
- f.ofMulEquivOfDom H = (f.comp k.toMonoidHom).toLocalizationMap ⋯ ⋯ ⋯
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Given AddCommMonoids M, P and AddSubmonoids S ⊆ M, T ⊆ P, if f : M →* N is a
Localization map for S and k : P ≃+ M is an isomorphism of AddCommMonoids such that
k(T) = S, f ∘ k is a Localization map for T.
Equations
- f.ofAddEquivOfDom H = (f.comp k.toAddMonoidHom).toLocalizationMap ⋯ ⋯ ⋯
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A special case of f ∘ id = f, f a Localization map.
A special case of f ∘ id = f, f a Localization map.
Given Localization maps f : M →* N, k : P →* U for Submonoids S, T respectively, an
isomorphism j : M ≃* P such that j(S) = T induces an isomorphism of localizations N ≃* U.
Equations
- f.mulEquivOfMulEquiv k H = f.mulEquivOfLocalizations (k.ofMulEquivOfDom H)
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Given Localization maps f : M →+ N, k : P →+ U for Submonoids S, T respectively, an
isomorphism j : M ≃+ P such that j(S) = T induces an isomorphism of localizations N ≃+ U.
Equations
- f.addEquivOfAddEquiv k H = f.addEquivOfLocalizations (k.ofAddEquivOfDom H)
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Natural homomorphism sending x : M, M a CommMonoid, to the equivalence class of
(x, 1) in the Localization of M at a Submonoid.
Equations
- Localization.monoidOf S = { toFun := fun (x : M) => Localization.mk x 1, map_one' := ⋯, map_mul' := ⋯, map_units' := ⋯, surj' := ⋯, exists_of_eq := ⋯ }
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Natural homomorphism sending x : M, M an AddCommMonoid, to the equivalence class of
(x, 0) in the Localization of M at a Submonoid.
Equations
- AddLocalization.addMonoidOf S = { toFun := fun (x : M) => AddLocalization.mk x 0, map_zero' := ⋯, map_add' := ⋯, map_add_units' := ⋯, surj' := ⋯, exists_of_eq := ⋯ }
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Given a Localization map f : M →* N for a Submonoid S, we get an isomorphism between
the Localization of M at S as a quotient type and N.
Equations
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Given a Localization map f : M →+ N for a Submonoid S, we get an isomorphism between
the Localization of M at S as a quotient type and N.
Equations
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The localization of a torsion-free monoid is torsion-free.
The localization of a torsion-free monoid is torsion-free.
Equations
- a.decidableEq b = a.recOnSubsingleton₂ b fun (x x_1 : α) (x_2 x_3 : ↥s) => decidable_of_iff' (↑x_3 * x = ↑x_2 * x_1) ⋯
Equations
- a.decidableEq b = a.recOnSubsingleton₂ b fun (x x_1 : α) (x_2 x_3 : ↥s) => decidable_of_iff' (↑x_3 + x = ↑x_2 + x_1) ⋯
The morphism numeratorHom is a monoid localization map in the case of commutative R.
Equations
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If R is commutative, Ore localization and monoid localization are isomorphic.