Centralizers of magmas and monoids #

Main definitions #

submonoid.centralizer: the centralizer of a subset of a monoid
add_submonoid.centralizer: the centralizer of a subset of an additive monoid

We provide subgroup.centralizer, add_subgroup.centralizer in other files.

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def submonoid.centralizer {M : Type u_1} (S : set M) [monoid M] :

submonoid M

The centralizer of a subset of a monoid M.

Equations

submonoid.centralizer S = {carrier := S.centralizer (mul_one_class.to_has_mul M), mul_mem' := _, one_mem' := _}

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def add_submonoid.centralizer {M : Type u_1} (S : set M) [add_monoid M] :

add_submonoid M

The centralizer of a subset of an additive monoid.

Equations

add_submonoid.centralizer S = {carrier := S.add_centralizer (add_zero_class.to_has_add M), add_mem' := _, zero_mem' := _}

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@[simp, norm_cast]

theorem add_submonoid.coe_centralizer {M : Type u_1} (S : set M) [add_monoid M] :

↑(add_submonoid.centralizer S) = S.add_centralizer

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@[simp, norm_cast]

theorem submonoid.coe_centralizer {M : Type u_1} (S : set M) [monoid M] :

↑(submonoid.centralizer S) = S.centralizer

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theorem submonoid.centralizer_to_subsemigroup {M : Type u_1} (S : set M) [monoid M] :

(submonoid.centralizer S).to_subsemigroup = subsemigroup.centralizer S

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theorem add_submonoid.centralizer_to_add_subsemigroup {M : Type u_1} [add_monoid M] (S : set M) :

(add_submonoid.centralizer S).to_add_subsemigroup = add_subsemigroup.centralizer S

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theorem submonoid.mem_centralizer_iff {M : Type u_1} {S : set M} [monoid M] {z : M} :

z ∈ submonoid.centralizer S ↔ ∀ (g : M), g ∈ S → g * z = z * g

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theorem add_submonoid.mem_centralizer_iff {M : Type u_1} {S : set M} [add_monoid M] {z : M} :

z ∈ add_submonoid.centralizer S ↔ ∀ (g : M), g ∈ S → g + z = z + g

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@[protected, instance]

def submonoid.decidable_mem_centralizer {M : Type u_1} {S : set M} [monoid M] [decidable_eq M] [fintype M] [decidable_pred (λ (_x : M), _x ∈ S)] :

decidable_pred (λ (_x : M), _x ∈ submonoid.centralizer S)

Equations

submonoid.decidable_mem_centralizer = λ (_x : M), decidable_of_iff' (∀ (g : M), g ∈ S → g * _x = _x * g) submonoid.mem_centralizer_iff

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@[protected, instance]

def add_submonoid.decidable_mem_centralizer {M : Type u_1} {S : set M} [add_monoid M] [decidable_eq M] [fintype M] [decidable_pred (λ (_x : M), _x ∈ S)] :

decidable_pred (λ (_x : M), _x ∈ add_submonoid.centralizer S)

Equations

add_submonoid.decidable_mem_centralizer = λ (_x : M), decidable_of_iff' (∀ (g : M), g ∈ S → g + _x = _x + g) add_submonoid.mem_centralizer_iff

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theorem add_submonoid.centralizer_le {M : Type u_1} {S T : set M} [add_monoid M] (h : S ⊆ T) :

add_submonoid.centralizer T ≤ add_submonoid.centralizer S

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theorem submonoid.centralizer_le {M : Type u_1} {S T : set M} [monoid M] (h : S ⊆ T) :

submonoid.centralizer T ≤ submonoid.centralizer S

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@[simp]

theorem submonoid.centralizer_univ (M : Type u_1) [monoid M] :

submonoid.centralizer set.univ = submonoid.center M

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@[simp]

theorem add_submonoid.centralizer_univ (M : Type u_1) [add_monoid M] :

add_submonoid.centralizer set.univ = add_submonoid.center M