Germ of a function at a filter #
The germ of a function f : α → β
at a filter l : Filter α
is the equivalence class of f
with respect to the equivalence relation EventuallyEq l
: f ≈ g
means ∀ᶠ x in l, f x = g x
.
Main definitions #
We define
Filter.Germ l β
to be the space of germs of functionsα → β
at a filterl : Filter α
;- coercion from
α → β
toGerm l β
:(f : Germ l β)
is the germ off : α → β
atl : Filter α
; this coercion is declared asCoeTC
; (const l c : Germ l β)
is the germ of the constant functionfun x : α ↦ c
at a filterl
;- coercion from
β
toGerm l β
:(↑c : Germ l β)
is the germ of the constant functionfun x : α ↦ c
at a filterl
; this coercion is declared asCoeTC
; map (F : β → γ) (f : Germ l β)
to be the composition of a functionF
and a germf
;map₂ (F : β → γ → δ) (f : Germ l β) (g : Germ l γ)
to be the germ offun x ↦ F (f x) (g x)
atl
;f.Tendsto lb
: we say that a germf : Germ l β
tends to a filterlb
if its representatives tend tolb
alongl
;f.compTendsto g hg
andf.compTendsto' g hg
: givenf : Germ l β
and a functiong : γ → α
(resp., a germg : Germ lc α
), ifg
tends tol
alonglc
, then the compositionf ∘ g
is a well-defined germ atlc
;Germ.liftPred
,Germ.liftRel
: lift a predicate or a relation to the space of germs:(f : Germ l β).liftPred p
means∀ᶠ x in l, p (f x)
, and similarly for a relation.
We also define map (F : β → γ) : Germ l β → Germ l γ
sending each germ f
to F ∘ f
.
For each of the following structures we prove that if β
has this structure, then so does
Germ l β
:
- one-operation algebraic structures up to
CommGroup
; MulZeroClass
,Distrib
,Semiring
,CommSemiring
,Ring
,CommRing
;MulAction
,DistribMulAction
,Module
;Preorder
,PartialOrder
, andLattice
structures, as well asBoundedOrder
;
Tags #
filter, germ
Setoid used to define the filter product. This is a dependent version of
Filter.germSetoid
.
Equations
Instances For
The filter product (a : α) → ε a
at a filter l
. This is a dependent version of
Filter.Germ
.
Instances For
Equations
- Filter.Product.instInhabited = { default := Quotient.mk' fun (a : α) => default }
A germ P
of functions α → β
is constant w.r.t. l
.
Equations
- P.IsConstant = Quotient.liftOn P (fun (f : α → β) => ∃ (b : β), f =ᶠ[l] fun (x : α) => b) ⋯
Instances For
Given a map F : (α → β) → (γ → δ)
that sends functions eventually equal at l
to functions
eventually equal at lc
, returns a map from Germ l β
to Germ lc δ
.
Equations
- Filter.Germ.map' F hF = Quotient.map' F hF
Instances For
Given a germ f : Germ l β
and a function F : (α → β) → γ
sending eventually equal functions
to the same value, returns the value F
takes on functions having germ f
at l
.
Equations
- f.liftOn F hF = Quotient.liftOn' f F hF
Instances For
Alias of the reverse direction of Filter.Germ.coe_eq
.
Lift a function β → γ
to a function Germ l β → Germ l γ
.
Equations
- Filter.Germ.map op = Filter.Germ.map' (fun (x : α → β) => op ∘ x) ⋯
Instances For
Lift a binary function β → γ → δ
to a function Germ l β → Germ l γ → Germ l δ
.
Equations
- Filter.Germ.map₂ op = Quotient.map₂ (fun (f : α → β) (g : α → γ) (x : α) => op (f x) (g x)) ⋯
Instances For
A germ at l
of maps from α
to β
tends to lb : Filter β
if it is represented by a map
which tends to lb
along l
.
Equations
- f.Tendsto lb = f.liftOn (fun (f : α → β) => Filter.Tendsto f l lb) ⋯
Instances For
Alias of the reverse direction of Filter.Germ.coe_tendsto
.
Given two germs f : Germ l β
, and g : Germ lc α
, where l : Filter α
, if g
tends to l
,
then the composition f ∘ g
is well-defined as a germ at lc
.
Equations
- f.compTendsto' g hg = f.liftOn (fun (f : α → β) => Filter.Germ.map f g) ⋯
Instances For
Given a germ f : Germ l β
and a function g : γ → α
, where l : Filter α
, if g
tends
to l
along lc : Filter γ
, then the composition f ∘ g
is well-defined as a germ at lc
.
Equations
- f.compTendsto g hg = f.compTendsto' ↑g ⋯
Instances For
If a germ f : Germ l β
is constant, where l : Filter α
,
and a function g : γ → α
tends to l
along lc : Filter γ
,
the germ of the composition f ∘ g
is also constant.
Lift a predicate on β
to Germ l β
.
Equations
- Filter.Germ.LiftPred p f = f.liftOn (fun (f : α → β) => ∀ᶠ (x : α) in l, p (f x)) ⋯
Instances For
Lift a relation r : β → γ → Prop
to Germ l β → Germ l γ → Prop
.
Equations
- Filter.Germ.LiftRel r f g = Quotient.liftOn₂' f g (fun (f : α → β) (g : α → γ) => ∀ᶠ (x : α) in l, r (f x) (g x)) ⋯
Instances For
Equations
- Filter.Germ.instMul = { mul := Filter.Germ.map₂ fun (x1 x2 : M) => x1 * x2 }
Equations
- Filter.Germ.instAdd = { add := Filter.Germ.map₂ fun (x1 x2 : M) => x1 + x2 }
Equations
- Filter.Germ.instSemigroup = Semigroup.mk ⋯
Equations
- Filter.Germ.instAddSemigroup = AddSemigroup.mk ⋯
Equations
- Filter.Germ.instCommSemigroup = CommSemigroup.mk ⋯
Equations
- Filter.Germ.instAddCommSemigroup = AddCommSemigroup.mk ⋯
Equations
- Filter.Germ.instLeftCancelSemigroup = LeftCancelSemigroup.mk ⋯
Equations
- Filter.Germ.instAddLeftCancelSemigroup = AddLeftCancelSemigroup.mk ⋯
Equations
- Filter.Germ.instRightCancelSemigroup = RightCancelSemigroup.mk ⋯
Equations
- Filter.Germ.instAddRightCancelSemigroup = AddRightCancelSemigroup.mk ⋯
Equations
- Filter.Germ.instMulOneClass = MulOneClass.mk ⋯ ⋯
Equations
- Filter.Germ.instAddZeroClass = AddZeroClass.mk ⋯ ⋯
Coercion from functions to germs as a monoid homomorphism.
Equations
- Filter.Germ.coeMulHom l = { toFun := Filter.Germ.ofFun, map_one' := ⋯, map_mul' := ⋯ }
Instances For
Coercion from functions to germs as an additive monoid homomorphism.
Equations
- Filter.Germ.coeAddHom l = { toFun := Filter.Germ.ofFun, map_zero' := ⋯, map_add' := ⋯ }
Instances For
Equations
- Filter.Germ.instCommMonoid = CommMonoid.mk ⋯
Equations
- Filter.Germ.instAddCommMonoid = AddCommMonoid.mk ⋯
Alias of Filter.Germ.natCast_def
.
Alias of Filter.Germ.intCast_def
.
Equations
- Filter.Germ.instAddMonoidWithOne = AddMonoidWithOne.mk ⋯ ⋯
Equations
- Filter.Germ.instAddCommMonoidWithOne = AddCommMonoidWithOne.mk ⋯
Equations
- Filter.Germ.instInv = { inv := Filter.Germ.map Inv.inv }
Equations
- Filter.Germ.instNeg = { neg := Filter.Germ.map Neg.neg }
Equations
- Filter.Germ.instDiv = { div := Filter.Germ.map₂ fun (x1 x2 : M) => x1 / x2 }
Equations
- Filter.Germ.instSub = { sub := Filter.Germ.map₂ fun (x1 x2 : M) => x1 - x2 }
Equations
- Filter.Germ.instInvolutiveInv = InvolutiveInv.mk ⋯
Equations
- Filter.Germ.instInvolutiveNeg = InvolutiveNeg.mk ⋯
Equations
- Filter.Germ.instHasDistribNeg = HasDistribNeg.mk ⋯ ⋯
Equations
- Filter.Germ.instInvOneClass = InvOneClass.mk ⋯
Equations
- Filter.Germ.instNegZeroClass = NegZeroClass.mk ⋯
Equations
- Filter.Germ.instDivInvMonoid = DivInvMonoid.mk ⋯ (fun (z : ℤ) (f : l.Germ G) => f ^ z) ⋯ ⋯ ⋯
Equations
- Filter.Germ.subNegMonoid = SubNegMonoid.mk ⋯ (fun (z : ℤ) (f : l.Germ G) => z • f) ⋯ ⋯ ⋯
Equations
- Filter.Germ.instDivisionMonoid = DivisionMonoid.mk ⋯ ⋯ ⋯
Equations
- Filter.Germ.instSubtractionMonoid = SubtractionMonoid.mk ⋯ ⋯ ⋯
Equations
- Filter.Germ.instAddGroup = AddGroup.mk ⋯
Equations
- Filter.Germ.instCommGroup = CommGroup.mk ⋯
Equations
- Filter.Germ.instAddCommGroup = AddCommGroup.mk ⋯
Equations
- Filter.Germ.instAddGroupWithOne = AddGroupWithOne.mk ⋯ SubNegMonoid.zsmul ⋯ ⋯ ⋯ ⋯ ⋯ ⋯
Equations
- Filter.Germ.instMulZeroClass = MulZeroClass.mk ⋯ ⋯
Equations
- Filter.Germ.instMulZeroOneClass = MulZeroOneClass.mk ⋯ ⋯
Equations
- Filter.Germ.instMonoidWithZero = MonoidWithZero.mk ⋯ ⋯
Equations
- Filter.Germ.instDistrib = Distrib.mk ⋯ ⋯
Equations
- Filter.Germ.instNonUnitalNonAssocSemiring = NonUnitalNonAssocSemiring.mk ⋯ ⋯ ⋯ ⋯
Equations
- Filter.Germ.instNonUnitalSemiring = NonUnitalSemiring.mk ⋯
Equations
- Filter.Germ.instNonAssocSemiring = NonAssocSemiring.mk ⋯ ⋯ ⋯ ⋯
Equations
- Filter.Germ.instNonUnitalNonAssocRing = NonUnitalNonAssocRing.mk ⋯ ⋯ ⋯ ⋯
Equations
- Filter.Germ.instNonUnitalRing = NonUnitalRing.mk ⋯
Equations
- Filter.Germ.instNonAssocRing = NonAssocRing.mk ⋯ ⋯ ⋯ ⋯ ⋯ ⋯
Equations
- Filter.Germ.instSemiring = Semiring.mk ⋯ ⋯ ⋯ ⋯ Monoid.npow ⋯ ⋯
Equations
- Filter.Germ.instNonUnitalCommSemiring = NonUnitalCommSemiring.mk ⋯
Equations
- Filter.Germ.instCommSemiring = CommSemiring.mk ⋯
Equations
- Filter.Germ.instNonUnitalCommRing = NonUnitalCommRing.mk ⋯
Equations
- Filter.Germ.instCommRing = CommRing.mk ⋯
Equations
- Filter.Germ.instDistribMulAction = DistribMulAction.mk ⋯ ⋯
Equations
- Filter.Germ.instDistribMulAction' = DistribMulAction.mk ⋯ ⋯
Equations
- Filter.Germ.instLE = { le := Filter.Germ.LiftRel fun (x1 x2 : β) => x1 ≤ x2 }
Equations
- Filter.Germ.instPreorder = Preorder.mk ⋯ ⋯ ⋯
Equations
- Filter.Germ.instPartialOrder = PartialOrder.mk ⋯
Equations
- Filter.Germ.instOrderBot = OrderBot.mk ⋯
Equations
- Filter.Germ.instOrderTop = OrderTop.mk ⋯
Equations
- Filter.Germ.instBoundedOrder = BoundedOrder.mk
Equations
- Filter.Germ.instSup = { max := Filter.Germ.map₂ fun (x1 x2 : β) => x1 ⊔ x2 }
Equations
- Filter.Germ.instInf = { min := Filter.Germ.map₂ fun (x1 x2 : β) => x1 ⊓ x2 }
Equations
- Filter.Germ.instSemilatticeSup = SemilatticeSup.mk max ⋯ ⋯ ⋯
Equations
- Filter.Germ.instSemilatticeInf = SemilatticeInf.mk min ⋯ ⋯ ⋯
Equations
- Filter.Germ.instLattice = Lattice.mk SemilatticeInf.inf ⋯ ⋯ ⋯
Equations
- Filter.Germ.instDistribLattice = DistribLattice.mk ⋯