Turning a preorder into a partial order

This file allows to make a preorder into a partial order by quotienting out the elements a, b such that a ≤ b and b ≤ a.

Antisymmetrization is a functor from Preorder to PartialOrder. See Preorder_to_PartialOrder.

Main declarations

• AntisymmRel: The antisymmetrization relation. AntisymmRel r a b means that a and b are related both ways by r.
• Antisymmetrization α r: The quotient of α by AntisymmRel r. Even when r is just a preorder, Antisymmetrization α is a partial order.

def AntisymmRel {α : Type u_1} (r : α → α → Prop) (a : α) (b : α) : Prop

The antisymmetrization relation.

Equations

• AntisymmRel r a b = (r a b ∧ r b a)

theorem antisymmRel_swap {α : Type u_1} (r : α → α → Prop) : AntisymmRel (Function.swap r) = AntisymmRel r

theorem antisymmRel_refl {α : Type u_1} (r : α → α → Prop) [IsRefl α r] (a : α) : AntisymmRel r a a

theorem AntisymmRel.symm {α : Type u_1} {r : α → α → Prop} {a : α} {b : α} : AntisymmRel r a b → AntisymmRel r b a

theorem AntisymmRel.trans {α : Type u_1} {r : α → α → Prop} [IsTrans α r] {a : α} {b : α} {c : α} (hab : AntisymmRel r a b) (hbc : AntisymmRel r b c) : AntisymmRel r a c

instance AntisymmRel.decidableRel {α : Type u_1} {r : α → α → Prop} [DecidableRel r] : DecidableRel (AntisymmRel r)

Equations

• AntisymmRel.decidableRel x✝ x = instDecidableAnd

@[simp]

theorem antisymmRel_iff_eq {α : Type u_1} {r : α → α → Prop} [IsRefl α r] [IsAntisymm α r] {a : α} {b : α} : AntisymmRel r a b ↔ a = b

theorem AntisymmRel.eq {α : Type u_1} {r : α → α → Prop} [IsRefl α r] [IsAntisymm α r] {a : α} {b : α} : AntisymmRel r a b → a = b

Alias of the forward direction of antisymmRel_iff_eq.

def AntisymmRel.setoid (α : Type u_1) (r : α → α → Prop) [IsPreorder α r] : Setoid α

The antisymmetrization relation as an equivalence relation.

Equations

• AntisymmRel.setoid α r = { r := AntisymmRel r, iseqv := ⋯ }

@[simp]

theorem AntisymmRel.setoid_r (α : Type u_1) (r : α → α → Prop) [IsPreorder α r] (a : α) (b : α) : (AntisymmRel.setoid α r) a b = AntisymmRel r a b

def Antisymmetrization (α : Type u_1) (r : α → α → Prop) [IsPreorder α r] : Type u_1

The partial order derived from a preorder by making pairwise comparable elements equal. This is the quotient by fun a b => a ≤ b ∧ b ≤ a.

Equations

• Antisymmetrization α r = Quotient (AntisymmRel.setoid α r)

def toAntisymmetrization {α : Type u_1} (r : α → α → Prop) [IsPreorder α r] : α → Antisymmetrization α r

Turn an element into its antisymmetrization.

Equations

• toAntisymmetrization r = Quotient.mk (AntisymmRel.setoid α r)

noncomputable def ofAntisymmetrization {α : Type u_1} (r : α → α → Prop) [IsPreorder α r] : Antisymmetrization α r → α

Get a representative from the antisymmetrization.

Equations

• ofAntisymmetrization r = Quotient.out'

instance instInhabitedAntisymmetrization {α : Type u_1} (r : α → α → Prop) [IsPreorder α r] [Inhabited α] : Inhabited (Antisymmetrization α r)

Equations

• instInhabitedAntisymmetrization r = id inferInstance

theorem Antisymmetrization.ind {α : Type u_1} (r : α → α → Prop) [IsPreorder α r] {p : Antisymmetrization α r → Prop} : (∀ (a : α), p (toAntisymmetrization r a)) → ∀ (q : Antisymmetrization α r), p q

theorem Antisymmetrization.induction_on {α : Type u_1} (r : α → α → Prop) [IsPreorder α r] {p : Antisymmetrization α r → Prop} (a : Antisymmetrization α r) (h : ∀ (a : α), p (toAntisymmetrization r a)) : p a

@[simp]

theorem toAntisymmetrization_ofAntisymmetrization {α : Type u_1} (r : α → α → Prop) [IsPreorder α r] (a : Antisymmetrization α r) : toAntisymmetrization r (ofAntisymmetrization r a) = a

theorem AntisymmRel.image {α : Type u_1} {β : Type u_2} [Preorder α] [Preorder β] {a : α} {b : α} (h : AntisymmRel (fun (x1 x2 : α) => x1 ≤ x2) a b) {f : α → β} (hf : Monotone f) : AntisymmRel (fun (x1 x2 : β) => x1 ≤ x2) (f a) (f b)

instance instPartialOrderAntisymmetrization {α : Type u_1} [Preorder α] : PartialOrder (Antisymmetrization α fun (x1 x2 : α) => x1 ≤ x2)

Equations

• instPartialOrderAntisymmetrization = PartialOrder.mk ⋯

theorem antisymmetrization_fibration {α : Type u_1} [Preorder α] : Relation.Fibration (fun (x1 x2 : α) => x1 < x2) (fun (x1 x2 : Antisymmetrization α fun (x1 x2 : α) => x1 ≤ x2) => x1 < x2) (toAntisymmetrization fun (x1 x2 : α) => x1 ≤ x2)

theorem acc_antisymmetrization_iff {α : Type u_1} [Preorder α] {a : α} : Acc (fun (x1 x2 : Antisymmetrization α fun (x1 x2 : α) => x1 ≤ x2) => x1 < x2) (toAntisymmetrization (fun (x1 x2 : α) => x1 ≤ x2) a) ↔ Acc (fun (x1 x2 : α) => x1 < x2) a

theorem wellFounded_antisymmetrization_iff {α : Type u_1} [Preorder α] : WellFounded LT.lt ↔ WellFounded LT.lt

instance instWellFoundedLTAntisymmetrizationLe {α : Type u_1} [Preorder α] [WellFoundedLT α] : WellFoundedLT (Antisymmetrization α fun (x1 x2 : α) => x1 ≤ x2)

Equations

• ⋯ = ⋯

instance instLinearOrderAntisymmetrizationLeOfDecidableRelLtOfIsTotal {α : Type u_1} [Preorder α] [DecidableRel fun (x1 x2 : α) => x1 ≤ x2] [DecidableRel fun (x1 x2 : α) => x1 < x2] [IsTotal α fun (x1 x2 : α) => x1 ≤ x2] : LinearOrder (Antisymmetrization α fun (x1 x2 : α) => x1 ≤ x2)

Equations

• One or more equations did not get rendered due to their size.

@[simp]

theorem toAntisymmetrization_le_toAntisymmetrization_iff {α : Type u_1} [Preorder α] {a : α} {b : α} : toAntisymmetrization (fun (x1 x2 : α) => x1 ≤ x2) a ≤ toAntisymmetrization (fun (x1 x2 : α) => x1 ≤ x2) b ↔ a ≤ b

@[simp]

theorem toAntisymmetrization_lt_toAntisymmetrization_iff {α : Type u_1} [Preorder α] {a : α} {b : α} : toAntisymmetrization (fun (x1 x2 : α) => x1 ≤ x2) a < toAntisymmetrization (fun (x1 x2 : α) => x1 ≤ x2) b ↔ a < b

@[simp]

theorem ofAntisymmetrization_le_ofAntisymmetrization_iff {α : Type u_1} [Preorder α] {a : Antisymmetrization α fun (x1 x2 : α) => x1 ≤ x2} {b : Antisymmetrization α fun (x1 x2 : α) => x1 ≤ x2} : ofAntisymmetrization (fun (x1 x2 : α) => x1 ≤ x2) a ≤ ofAntisymmetrization (fun (x1 x2 : α) => x1 ≤ x2) b ↔ a ≤ b

@[simp]

theorem ofAntisymmetrization_lt_ofAntisymmetrization_iff {α : Type u_1} [Preorder α] {a : Antisymmetrization α fun (x1 x2 : α) => x1 ≤ x2} {b : Antisymmetrization α fun (x1 x2 : α) => x1 ≤ x2} : ofAntisymmetrization (fun (x1 x2 : α) => x1 ≤ x2) a < ofAntisymmetrization (fun (x1 x2 : α) => x1 ≤ x2) b ↔ a < b

theorem toAntisymmetrization_mono {α : Type u_1} [Preorder α] : Monotone (toAntisymmetrization fun (x1 x2 : α) => x1 ≤ x2)

def OrderHom.antisymmetrization {α : Type u_1} {β : Type u_2} [Preorder α] [Preorder β] (f : α →o β) : (Antisymmetrization α fun (x1 x2 : α) => x1 ≤ x2) →o Antisymmetrization β fun (x1 x2 : β) => x1 ≤ x2

Turns an order homomorphism from α to β into one from Antisymmetrization α to Antisymmetrization β. Antisymmetrization is actually a functor. See Preorder_to_PartialOrder.

Equations

• f.antisymmetrization = { toFun := Quotient.map' ⇑f ⋯, monotone' := ⋯ }

@[simp]

theorem OrderHom.coe_antisymmetrization {α : Type u_1} {β : Type u_2} [Preorder α] [Preorder β] (f : α →o β) : ⇑f.antisymmetrization = Quotient.map' ⇑f ⋯

theorem OrderHom.antisymmetrization_apply {α : Type u_1} {β : Type u_2} [Preorder α] [Preorder β] (f : α →o β) (a : Antisymmetrization α fun (x1 x2 : α) => x1 ≤ x2) : f.antisymmetrization a = Quotient.map' ⇑f ⋯ a

@[simp]

theorem OrderHom.antisymmetrization_apply_mk {α : Type u_1} {β : Type u_2} [Preorder α] [Preorder β] (f : α →o β) (a : α) : f.antisymmetrization (toAntisymmetrization (fun (x1 x2 : α) => x1 ≤ x2) a) = toAntisymmetrization (fun (x1 x2 : β) => x1 ≤ x2) (f a)

noncomputable def OrderEmbedding.ofAntisymmetrization (α : Type u_1) [Preorder α] : (Antisymmetrization α fun (x1 x2 : α) => x1 ≤ x2) ↪o α

ofAntisymmetrization as an order embedding.

Equations

• OrderEmbedding.ofAntisymmetrization α = { toFun := ofAntisymmetrization fun (x1 x2 : α) => x1 ≤ x2, inj' := ⋯, map_rel_iff' := ⋯ }

@[simp]

theorem OrderEmbedding.ofAntisymmetrization_apply (α : Type u_1) [Preorder α] : ∀ (a : Antisymmetrization α fun (x1 x2 : α) => x1 ≤ x2), (OrderEmbedding.ofAntisymmetrization α) a = ofAntisymmetrization (fun (x1 x2 : α) => x1 ≤ x2) a

def OrderIso.dualAntisymmetrization (α : Type u_1) [Preorder α] : (Antisymmetrization α fun (x1 x2 : α) => x1 ≤ x2)ᵒᵈ ≃o Antisymmetrization αᵒᵈ fun (x1 x2 : αᵒᵈ) => x1 ≤ x2

Antisymmetrization and orderDual commute.

Equations

• OrderIso.dualAntisymmetrization α = { toFun := Quotient.map' id ⋯, invFun := Quotient.map' id ⋯, left_inv := ⋯, right_inv := ⋯, map_rel_iff' := ⋯ }

@[simp]

theorem OrderIso.dualAntisymmetrization_apply (α : Type u_1) [Preorder α] (a : α) : (OrderIso.dualAntisymmetrization α) (OrderDual.toDual (toAntisymmetrization (fun (x1 x2 : α) => x1 ≤ x2) a)) = toAntisymmetrization (fun (x1 x2 : αᵒᵈ) => x1 ≤ x2) (OrderDual.toDual a)

@[simp]

theorem OrderIso.dualAntisymmetrization_symm_apply (α : Type u_1) [Preorder α] (a : α) : (OrderIso.dualAntisymmetrization α).symm (toAntisymmetrization (fun (x1 x2 : αᵒᵈ) => x1 ≤ x2) (OrderDual.toDual a)) = OrderDual.toDual (toAntisymmetrization (fun (x1 x2 : α) => x1 ≤ x2) a)