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

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

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

theorem mem_or_inv_mem {S : Type u_1} {G : Type u_2} [CommGroup G] [SetLike S G] (C : S) [IsMaxMulCone C] (a : G) : a ∈ C ∨ a⁻¹ ∈ C

theorem mem_or_neg_mem {S : Type u_1} {G : Type u_2} [AddCommGroup G] [SetLike S G] (C : S) [IsMaxCone C] (a : G) : a ∈ C ∨ -a ∈ C

def GroupCone.oneLE (H : Type u_1) [CommGroup H] [PartialOrder H] [IsOrderedMonoid H] : GroupCone H

The cone of elements that are at least 1.

def AddGroupCone.nonneg (H : Type u_1) [AddCommGroup H] [PartialOrder H] [IsOrderedAddMonoid H] : AddGroupCone H

The cone of non-negative elements.

@[simp]

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

@[simp]

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

@[simp]

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

@[simp]

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

@[simp]

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

@[simp]

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

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

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

@[reducible, inline]

abbrev PartialOrder.mkOfGroupCone {S : Type u_1} {G : Type u_2} [CommGroup G] [SetLike S G] (C : S) [GroupConeClass S G] : PartialOrder G

Construct a partial order by designating a cone in an abelian group.

@[reducible, inline]

abbrev PartialOrder.mkOfAddGroupCone {S : Type u_1} {G : Type u_2} [AddCommGroup G] [SetLike S G] (C : S) [AddGroupConeClass S G] : PartialOrder G

Construct a partial order by designating a cone in an abelian group.

@[simp]

theorem PartialOrder.mkOfGroupCone_le_iff {S : Type u_3} {G : Type u_4} [CommGroup G] [SetLike S G] [GroupConeClass S G] {C : S} {a b : G} : a ≤ b ↔ b / a ∈ C

@[simp]

theorem PartialOrder.mkOfAddGroupCone_le_iff {S : Type u_3} {G : Type u_4} [AddCommGroup G] [SetLike S G] [AddGroupConeClass S G] {C : S} {a b : G} : a ≤ b ↔ b - a ∈ C

@[reducible, inline]

abbrev LinearOrder.mkOfGroupCone {S : Type u_1} {G : Type u_2} [CommGroup G] [SetLike S G] (C : S) [GroupConeClass S G] [IsMaxMulCone C] [DecidablePred fun (x : G) => x ∈ C] : LinearOrder G

Construct a linear order by designating a maximal cone in an abelian group.

@[reducible, inline]

abbrev LinearOrder.mkOfAddGroupCone {S : Type u_1} {G : Type u_2} [AddCommGroup G] [SetLike S G] (C : S) [AddGroupConeClass S G] [IsMaxCone C] [DecidablePred fun (x : G) => x ∈ C] : LinearOrder G

Construct a linear order by designating a maximal cone in an abelian group.

theorem IsOrderedMonoid.mkOfCone {S : Type u_1} {G : Type u_2} [CommGroup G] [SetLike S G] (C : S) [GroupConeClass S G] : have x := PartialOrder.mkOfGroupCone C; IsOrderedMonoid G

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

theorem IsOrderedAddMonoid.mkOfCone {S : Type u_1} {G : Type u_2} [AddCommGroup G] [SetLike S G] (C : S) [AddGroupConeClass S G] : have x := PartialOrder.mkOfAddGroupCone C; IsOrderedAddMonoid G

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