Local diffeomorphisms between manifolds #
In this file, we define C^n local diffeomorphisms between manifolds.
A C^n map f : M → N is a local diffeomorphism at x iff there are neighbourhoods s
and t of x and f x, respectively such that f restricts to a diffeomorphism
between s and t. f is called a local diffeomorphism on s iff it is a local diffeomorphism
at every x ∈ s, and a local diffeomorphism iff it is a local diffeomorphism on univ.
Main definitions #
IsLocalDiffeomorphAt I J n f x:fis aC^nlocal diffeomorphism atxIsLocalDiffeomorphOn I J n f s:fis aC^nlocal diffeomorphism onsIsLocalDiffeomorph I J n f:fis aC^nlocal diffeomorphism
Main results #
Each of
Diffeomorph,IsLocalDiffeomorph,IsLocalDiffeomorphOnandIsLocalDiffeomorphAtimplies the next condition.IsLocalDiffeomorph.isLocalHomeomorph: a local diffeomorphisms is a local homeomorphism, similarly for local diffeomorphism onsIsLocalDiffeomorph.isOpen_range: the image of a local diffeomorphism is openIslocalDiffeomorph.diffeomorph_of_bijective: a bijective local diffeomorphism is a diffeomorphismDiffeomorph.mfderivToContinuousLinearEquiv: each differential of aC^ndiffeomorphism (n ≥ 1) is a linear equivalence.LocalDiffeomorphAt.mfderivToContinuousLinearEquiv: iffis a local diffeomorphism atx, the differentialmfderiv I J n f xis a continuous linear equivalence.LocalDiffeomorph.mfderivToContinuousLinearEquiv: iffis a local diffeomorphism, each differentialmfderiv I J n f xis a continuous linear equivalence.
TODO #
- an injective local diffeomorphism is a diffeomorphism to its image
- if
fisC^natxandmfderiv I J n f xis a linear isomorphism,fis a local diffeomorphism atx(using the inverse function theorem).
Implementation notes #
This notion of diffeomorphism is needed although there is already a notion of local structomorphism
because structomorphisms do not allow the model spaces H and H' of the two manifolds to be
different, i.e. for a structomorphism one has to impose H = H' which is often not the case in
practice.
Tags #
local diffeomorphism, manifold
A partial diffeomorphism on s is a function f : M → N such that f restricts to a
diffeomorphism s → t between open subsets of M and N, respectively.
This is an auxiliary definition and should not be used outside of this file.
- toFun : M → N
- invFun : N → M
- contMDiffOn_toFun : ContMDiffOn I J n (↑self.toPartialEquiv) self.source
- contMDiffOn_invFun : ContMDiffOn J I n self.invFun self.target
Instances For
Coercion of a PartialDiffeomorph to function.
Note that a PartialDiffeomorph is not DFunLike (like PartialHomeomorph),
as toFun doesn't determine invFun outside of target.
Equations
- instCoeFunPartialDiffeomorphForall I J M N n = { coe := fun (Φ : PartialDiffeomorph I J M N n) => ↑Φ.toPartialEquiv }
A diffeomorphism is a partial diffeomorphism.
Equations
- h.toPartialDiffeomorph = { toPartialEquiv := h.toHomeomorph.toPartialEquiv, open_source := ⋯, open_target := ⋯, contMDiffOn_toFun := ⋯, contMDiffOn_invFun := ⋯ }
Instances For
A partial diffeomorphism is also a local homeomorphism.
Equations
- Φ.toPartialHomeomorph = { toPartialEquiv := Φ.toPartialEquiv, open_source := ⋯, open_target := ⋯, continuousOn_toFun := ⋯, continuousOn_invFun := ⋯ }
Instances For
The inverse of a local diffeomorphism.
Equations
Instances For
f : M → N is called a C^n local diffeomorphism at x iff there exist
open sets U ∋ x and V ∋ f x and a diffeomorphism Φ : U → V such that f = Φ on U.
Equations
- IsLocalDiffeomorphAt I J n f x = ∃ (Φ : PartialDiffeomorph I J M N n), x ∈ Φ.source ∧ Set.EqOn f (↑Φ.toPartialEquiv) Φ.source
Instances For
An arbitrary choice of local inverse of f near x.
Equations
- hf.localInverse = (Classical.choose hf).symm
Instances For
f : M → N is called a C^n local diffeomorphism on s iff it is a local diffeomorphism
at each x : s.
Equations
- IsLocalDiffeomorphOn I J n f s = ∀ (x : ↑s), IsLocalDiffeomorphAt I J n f ↑x
Instances For
f : M → N is a C^n local diffeomorphism iff it is a local diffeomorphism
at each x ∈ M.
Equations
- IsLocalDiffeomorph I J n f = ∀ (x : M), IsLocalDiffeomorphAt I J n f x
Instances For
Basic properties of local diffeomorphisms #
A C^n local diffeomorphism at x is C^n differentiable at x.
A local diffeomorphism at x is differentiable at x.
A C^n local diffeomorphism on s is C^n on s.
A local diffeomorphism on s is differentiable on s.
A C^n local diffeomorphism is C^n.
A C^n local diffeomorphism is differentiable.
A C^n diffeomorphism is a local diffeomorphism.
A local diffeomorphism on s is a local homeomorphism on s.
A local diffeomorphism is a local homeomorphism.
A local diffeomorphism is an open map.
A local diffeomorphism has open range.
The image of a local diffeomorphism is open.
Instances For
A bijective local diffeomorphism is a diffeomorphism.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Alias of IsLocalDiffeomorph.diffeomorph_of_bijective.
A bijective local diffeomorphism is a diffeomorphism.
Equations
Instances For
If f is a C^n local diffeomorphism at x, for n ≥ 1, the differential df_x
is a linear equivalence.
Equations
- One or more equations did not get rendered due to their size.
Instances For
Each differential of a C^n diffeomorphism of Banach manifolds (n ≥ 1)
is a linear equivalence.
Equations
Instances For
If f is a C^n local diffeomorphism of Banach manifolds (n ≥ 1),
each differential is a linear equivalence.