Tangent bundles #
This file defines the tangent bundle as a smooth vector bundle.
Let M
be a smooth manifold with corners with model I
on (E, H)
. We define the tangent bundle
of M
using the VectorBundleCore
construction indexed by the charts of M
with fibers E
.
Given two charts i, j : LocalHomeomorph M H
, the coordinate change between i
and j
at a point
x : M
is the derivative of the composite
I.symm i.symm j I
E -----> H -----> M --> H --> E
within the set range I ⊆ E
at I (i x) : E
.
This defines a smooth vector bundle TangentBundle
with fibers TangentSpace
.
Main definitions #
-
TangentSpace I M x
is the fiber of the tangent bundle atx : M
, which is defined to beE
. -
TangentBundle I M
is the total space ofTangentSpace I M
, proven to be a smooth vector bundle.
Auxiliary lemma for tangent spaces: the derivative of a coordinate change between two charts is smooth on its source.
Let M
be a smooth manifold with corners with model I
on (E, H)
.
Then VectorBundleCore I M
is the vector bundle core for the tangent bundle over M
.
It is indexed by the atlas of M
, with fiber E
and its change of coordinates from the chart i
to the chart j
at point x : M
is the derivative of the composite
I.symm i.symm j I
E -----> H -----> M --> H --> E
within the set range I ⊆ E
at I (i x) : E
.
Instances For
The tangent space at a point of the manifold M
. It is just E
. We could use instead
(tangentBundleCore I M).to_topological_vector_bundle_core.fiber x
, but we use E
to help the
kernel.
Instances For
The tangent bundle to a smooth manifold, as a Sigma type. Defined in terms of
Bundle.TotalSpace
to be able to put a suitable topology on it.
Instances For
The tangent bundle to the model space #
In the tangent bundle to the model space, the charts are just the canonical identification
between a product type and a sigma type, a.k.a. TotalSpace.toProd
.
The canonical identification between the tangent bundle to the model space and the product, as a homeomorphism
Instances For
The map in_coordinates
for the tangent bundle is trivial on the model spaces
When ϕ x
is a continuous linear map that changes vectors in charts around f x
to vectors
in charts around g x
, inTangentCoordinates I I' f g ϕ x₀ x
is a coordinate change of
this continuous linear map that makes sense from charts around f x₀
to charts around g x₀
by composing it with appropriate coordinate changes.
Note that the type of ϕ
is more accurately
Π x : N, TangentSpace I (f x) →L[𝕜] TangentSpace I' (g x)
.
We are unfolding TangentSpace
in this type so that Lean recognizes that the type of ϕ
doesn't
actually depend on f
or g
.
This is the underlying function of the trivializations of the hom of (pullbacks of) tangent spaces.