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
:f
is aC^n
local diffeomorphism atx
IsLocalDiffeomorphOn I J n f s
:f
is aC^n
local diffeomorphism ons
IsLocalDiffeomorph I J n f
:f
is aC^n
local diffeomorphism
Main results #
- Each of
Diffeomorph
,IsLocalDiffeomorph
,IsLocalDiffeomorphOn
andIsLocalDiffeomorphAt
implies the next. IsLocalDiffeomorph.isLocalHomeomorph
: a local diffeomorphisms is a local homeomorphism, similarly for local diffeomorphism ons
IsLocalDiffeomorph.isOpen_range
: the image of a local diffeomorphism is openIslocalDiffeomorph.diffeomorph_of_bijective
: a bijective local diffeomorphism is a diffeomorphism
TODO #
- an injective local diffeomorphism is a diffeomorphism to its image
- each differential of a
C^n
diffeomorphism (n ≥ 1
) is a linear equivalence. - if
f
is a local diffeomorphism atx
, the differentialmfderiv I J n f x
is a continuous linear isomorphism. - conversely, if
f
isC^n
atx
andmfderiv I J n f x
is a linear isomorphism,f
is a local diffeomorphism atx
. - if
f
is a local diffeomorphism, each differentialmfderiv I J n f x
is a continuous linear isomorphism. - Conversely, if
f
isC^n
and each differential is a linear isomorphism,f
is a local diffeomorphism.
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
- open_source : IsOpen self.source
- open_target : IsOpen self.target
- 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
- Φ.symm = { toPartialEquiv := Φ.symm, open_source := ⋯, open_target := ⋯, contMDiffOn_toFun := ⋯, contMDiffOn_invFun := ⋯ }
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
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.