Construct ordered groups from groups with a specified positive cone.

In this file we provide the structure GroupCone and the predicate IsMaxCone that encode axioms of OrderedCommGroup and LinearOrderedCommGroup in terms of the subset of non-negative elements.

We also provide constructors that convert between cones in groups and the corresponding ordered groups.

class AddGroupConeClass (S : Type u_1) (G : outParam (Type u_2)) [AddCommGroup G] [SetLike S G] extends AddSubmonoidClass S G : Prop

AddGroupConeClass S G says that S is a type of cones in G.

• add_mem {s : S} {a b : G} : a ∈ s → b ∈ s → a + b ∈ s
• zero_mem (s : S) : 0 ∈ s
• eq_zero_of_mem_of_neg_mem {C : S} {a : G} : a ∈ C → -a ∈ C → a = 0

class GroupConeClass (S : Type u_1) (G : outParam (Type u_2)) [CommGroup G] [SetLike S G] extends SubmonoidClass S G : Prop

GroupConeClass S G says that S is a type of cones in G.

• mul_mem {s : S} {a b : G} : a ∈ s → b ∈ s → a * b ∈ s
• one_mem (s : S) : 1 ∈ s
• eq_one_of_mem_of_inv_mem {C : S} {a : G} : a ∈ C → a⁻¹ ∈ C → a = 1

structure AddGroupCone (G : Type u_1) [AddCommGroup G] extends AddSubmonoid G : Type u_1

A (positive) cone in an abelian group is a submonoid that does not contain both a and -a for any nonzero a. This is equivalent to being the set of non-negative elements of some order making the group into a partially ordered group.

• carrier : Set G
• add_mem' {a b : G} : a ∈ self.carrier → b ∈ self.carrier → a + b ∈ self.carrier
• zero_mem' : 0 ∈ self.carrier
• eq_zero_of_mem_of_neg_mem' {a : G} : a ∈ self.carrier → -a ∈ self.carrier → a = 0

structure GroupCone (G : Type u_1) [CommGroup G] extends Submonoid G : Type u_1

A (positive) cone in an abelian group is a submonoid that does not contain both a and a⁻¹ for any non-identity a. This is equivalent to being the set of elements that are at least 1 in some order making the group into a partially ordered group.

• carrier : Set G
• mul_mem' {a b : G} : a ∈ self.carrier → b ∈ self.carrier → a * b ∈ self.carrier
• one_mem' : 1 ∈ self.carrier
• eq_one_of_mem_of_inv_mem' {a : G} : a ∈ self.carrier → a⁻¹ ∈ self.carrier → a = 1

instance GroupCone.instSetLike (G : Type u_1) [CommGroup G] : SetLike (GroupCone G) G

Equations

• GroupCone.instSetLike G = { coe := fun (C : GroupCone G) => C.carrier, coe_injective' := ⋯ }

instance AddGroupCone.instSetLike (G : Type u_1) [AddCommGroup G] : SetLike (AddGroupCone G) G

Equations

• AddGroupCone.instSetLike G = { coe := fun (C : AddGroupCone G) => C.carrier, coe_injective' := ⋯ }

instance GroupCone.instGroupConeClass (G : Type u_1) [CommGroup G] : GroupConeClass (GroupCone G) G

instance AddGroupCone.instAddGroupConeClass (G : Type u_1) [AddCommGroup G] : AddGroupConeClass (AddGroupCone G) G

class IsMaxCone {S : Type u_1} {G : Type u_2} [AddCommGroup G] [SetLike S G] (C : S) : Prop

Typeclass for maximal additive cones.

• mem_or_neg_mem (a : G) : a ∈ C ∨ -a ∈ C

class IsMaxMulCone {S : Type u_1} {G : Type u_2} [CommGroup G] [SetLike S G] (C : S) : Prop

Typeclass for maximal multiplicative cones.

• mem_or_inv_mem (a : G) : a ∈ C ∨ a⁻¹ ∈ C

def GroupCone.oneLE (H : Type u_1) [OrderedCommGroup H] : GroupCone H

Construct a cone from the set of elements of a partially ordered abelian group that are at least 1.

Equations

• GroupCone.oneLE H = { toSubmonoid := Submonoid.oneLE H, eq_one_of_mem_of_inv_mem' := ⋯ }

def AddGroupCone.nonneg (H : Type u_1) [OrderedAddCommGroup H] : AddGroupCone H

Construct a cone from the set of non-negative elements of a partially ordered abelian group.

Equations

• AddGroupCone.nonneg H = { toAddSubmonoid := AddSubmonoid.nonneg H, eq_zero_of_mem_of_neg_mem' := ⋯ }

@[simp]

theorem GroupCone.oneLE_toSubmonoid {H : Type u_1} [OrderedCommGroup H] : (GroupCone.oneLE H).toSubmonoid = Submonoid.oneLE H

@[simp]

theorem AddGroupCone.nonneg_toAddSubmonoid {H : Type u_1} [OrderedAddCommGroup H] : (AddGroupCone.nonneg H).toAddSubmonoid = AddSubmonoid.nonneg H

@[simp]

theorem GroupCone.mem_oneLE {H : Type u_1} [OrderedCommGroup H] {a : H} : a ∈ GroupCone.oneLE H ↔ 1 ≤ a

@[simp]

theorem AddGroupCone.mem_nonneg {H : Type u_1} [OrderedAddCommGroup H] {a : H} : a ∈ AddGroupCone.nonneg H ↔ 0 ≤ a

@[simp]

theorem GroupCone.coe_oneLE {H : Type u_1} [OrderedCommGroup H] : ↑(GroupCone.oneLE H) = {x : H | 1 ≤ x}

@[simp]

theorem AddGroupCone.coe_nonneg {H : Type u_1} [OrderedAddCommGroup H] : ↑(AddGroupCone.nonneg H) = {x : H | 0 ≤ x}

instance GroupCone.oneLE.isMaxMulCone {H : Type u_2} [LinearOrderedCommGroup H] : IsMaxMulCone (GroupCone.oneLE H)

instance AddGroupCone.nonneg.isMaxCone {H : Type u_2} [LinearOrderedAddCommGroup H] : IsMaxCone (AddGroupCone.nonneg H)

@[reducible]

def OrderedCommGroup.mkOfCone {S : Type u_1} {G : Type u_2} [CommGroup G] [SetLike S G] (C : S) [GroupConeClass S G] : OrderedCommGroup G

Construct a partially ordered abelian group by designating a cone in an abelian group.

Equations

• OrderedCommGroup.mkOfCone C = OrderedCommGroup.mk ⋯

@[reducible]

def OrderedAddCommGroup.mkOfCone {S : Type u_1} {G : Type u_2} [AddCommGroup G] [SetLike S G] (C : S) [AddGroupConeClass S G] : OrderedAddCommGroup G

Construct a partially ordered abelian group by designating a cone in an abelian group.

Equations

• OrderedAddCommGroup.mkOfCone C = OrderedAddCommGroup.mk ⋯

@[reducible]

def LinearOrderedCommGroup.mkOfCone {S : Type u_1} {G : Type u_2} [CommGroup G] [SetLike S G] (C : S) [GroupConeClass S G] [IsMaxMulCone C] (dec : DecidablePred fun (x : G) => x ∈ C) : LinearOrderedCommGroup G

Construct a linearly ordered abelian group by designating a maximal cone in an abelian group.

Equations

• LinearOrderedCommGroup.mkOfCone C dec = LinearOrderedCommGroup.mk ⋯ (fun (x x_1 : G) => dec (x_1 / x)) decidableEqOfDecidableLE decidableLTOfDecidableLE ⋯ ⋯ ⋯

@[reducible]

def LinearOrderedAddCommGroup.mkOfCone {S : Type u_1} {G : Type u_2} [AddCommGroup G] [SetLike S G] (C : S) [AddGroupConeClass S G] [IsMaxCone C] (dec : DecidablePred fun (x : G) => x ∈ C) : LinearOrderedAddCommGroup G

Construct a linearly ordered abelian group by designating a maximal cone in an abelian group.

Equations

• LinearOrderedAddCommGroup.mkOfCone C dec = LinearOrderedAddCommGroup.mk ⋯ (fun (x x_1 : G) => dec (x_1 - x)) decidableEqOfDecidableLE decidableLTOfDecidableLE ⋯ ⋯ ⋯