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Mathlib.Algebra.GroupWithZero.Range

The range of a MonoidHomWithZero #

Given a MonoidWithZeroHom f : A → B whose codomain B is a MonoidWithZero, we define the type MonoidHomWithZero.valueMonoid as the submonoid of generated by the invertible elements in the range of f. For example, if A = ℕ, f is the natural cast to B where B is

MonoidHomWithZero.valueMonoid₀ is the MonoidWithZero obtained by adjoining 0 to the previous type.

Likewise, MonoidHomWithZero.valueGroup is the subgroup of generated by the invertible elements in range f and ``MonoidHomWithZero.valueGroup₀adds a0` to the previous group.

When B is commutative, then both MonoidHomWithZero.valueGroup f and MonoidHomWithZero.valueGroup₀ f are also commutative and the former can be described more explicitly (see MonoidHomWithZero.mem_valueGroup_iff_of_comm).

Main Results #

Implementation details #

MonoidHomWithZero.valueMonoid is defined explicitely in terms of its carrier, by proving the required properties; that it coincides with the submonoid generated by the closure is proven in MonoidHomWithZero.valueMonoid_eq_closure, but using the latter as definition yields to unwanted unfolding.

def MonoidHomWithZero.valueMonoid {A : Type u_1} {B : Type u_2} {F : Type u_3} [FunLike F A B] (f : F) [MonoidWithZero A] [MonoidWithZero B] [MonoidWithZeroHomClass F A B] :

For a morphism of monoids with zero f, this is a smallest submonoid of the invertible elements in the codomain containing the range of f.

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Instances For
    def MonoidHomWithZero.valueGroup {A : Type u_1} {B : Type u_2} {F : Type u_3} [FunLike F A B] (f : F) [MonoidWithZero A] [MonoidWithZero B] [MonoidWithZeroHomClass F A B] :

    For a morphism of monoids with zero f, this is the smallest subgroup of the invertible elements in the codomain containing the range of f.

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      @[reducible, inline]
      abbrev MonoidHomWithZero.valueMonoid₀ {A : Type u_1} {B : Type u_2} {F : Type u_3} [FunLike F A B] (f : F) [MonoidWithZero A] [MonoidWithZero B] [MonoidWithZeroHomClass F A B] :
      Type u_2

      For a morphism of monoids with zero f, this is the smallest submonoid with zero of the codomain containing the range of f.

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      Instances For
        @[reducible, inline]
        abbrev MonoidHomWithZero.valueGroup₀ {A : Type u_1} {B : Type u_2} {F : Type u_3} [FunLike F A B] (f : F) [MonoidWithZero A] [MonoidWithZero B] [MonoidWithZeroHomClass F A B] :
        Type u_2

        For a morphism of monoids with zero f, this is a smallest subgroup with zero of the codomain containing the range of f.

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          theorem MonoidHomWithZero.mem_valueMonoid {A : Type u_1} {B : Type u_2} {F : Type u_3} [FunLike F A B] (f : F) [MonoidWithZero A] [MonoidWithZero B] [MonoidWithZeroHomClass F A B] {b : Bˣ} (hb : b Set.range f) :
          theorem MonoidHomWithZero.mem_valueGroup {A : Type u_1} {B : Type u_2} {F : Type u_3} [FunLike F A B] (f : F) [MonoidWithZero A] [MonoidWithZero B] [MonoidWithZeroHomClass F A B] {b : Bˣ} (hb : b Set.range f) :
          theorem MonoidHomWithZero.inv_mem_valueGroup {A : Type u_1} {B : Type u_2} {F : Type u_3} [FunLike F A B] (f : F) [MonoidWithZero A] [MonoidWithZero B] [MonoidWithZeroHomClass F A B] {b : Bˣ} (hb : b Set.range f) :
          theorem MonoidHomWithZero.valueMonoid_eq_valueGroup' {A : Type u_1} {B : Type u_2} {F : Type u_3} [FunLike F A B] (f : F) [GroupWithZero A] [GroupWithZero B] [MonoidWithZeroHomClass F A B] :
          (valueMonoid f) = (valueGroup f)
          theorem MonoidHomWithZero.valueGroup_eq_range {A : Type u_1} {B : Type u_2} {F : Type u_3} [FunLike F A B] {f : F} [GroupWithZero A] [GroupWithZero B] [MonoidWithZeroHomClass F A B] :
          theorem MonoidHomWithZero.mem_valueGroup_iff_of_comm {A : Type u_1} {B : Type u_2} {F : Type u_3} [FunLike F A B] (f : F) [MonoidWithZero A] [CommGroupWithZero B] [MonoidWithZeroHomClass F A B] {y : Bˣ} :
          y valueGroup f ∃ (a : A), f a 0 ∃ (x : A), f a * y = f x
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          • One or more equations did not get rendered due to their size.