Vector fields in manifolds #
We study functions of the form V : Π (x : M) → TangentSpace I x
on a manifold, i.e.,
vector fields.
We define the pullback of a vector field under a map, as
VectorField.mpullback I I' f V x := (mfderiv I I' f x).inverse (V (f x))
(together with the same notion within a set). Note that the pullback uses the junk-value pattern:
if the derivative of the map is not invertible, then pullback is given the junk value zero.
We start developing API around this notion.
All these are given in the VectorField
namespace because pullbacks, Lie brackets, and so on,
are notions that make sense in a variety of contexts. We also prefix the notions with m
to
distinguish the manifold notions from the vector space notions.
For notions that come naturally in other namespaces for dot notation, we specify vectorField
in
the name to lift ambiguities. For instance, the fact that the Lie bracket of two smooth vector
fields is smooth will be ContMDiffAt.mlieBracket_vectorField
.
Note that a smoothness assumption for a vector field is written by seeing the vector field as
a function from M
to its tangent bundle through a coercion, as in:
MDifferentiableWithinAt I I.tangent (fun y ↦ (V y : TangentBundle I M)) s x
.
Pullback of vector fields in manifolds #
The pullback of a vector field under a map between manifolds, within a set s
. If the
derivative of the map within s
is not invertible, then pullback is given the junk value zero.
Equations
- VectorField.mpullbackWithin I I' f V s x = (mfderivWithin I I' f s x).inverse (V (f x))
Instances For
The pullback of a vector field under a map between manifolds. If the derivative of the map is not invertible, then pullback is given the junk value zero.
Equations
- VectorField.mpullback I I' f V x = (mfderiv I I' f x).inverse (V (f x))
Instances For
Regularity of pullback of vector fields #
In this paragraph, we assume that the model space is complete, to ensure that the set of invertible linear maps is open and that inversion is a smooth map there. Otherwise, the pullback of vector fields could behave wildly, even at points where the derivative of the map is invertible.
The pullback of a differentiable vector field by a C^n
function with 2 ≤ n
is
differentiable. Version within a set at a point.
The pullback of a differentiable vector field by a C^n
function with 2 ≤ n
is
differentiable. Version on a set.
The pullback of a differentiable vector field by a C^n
function with 2 ≤ n
is
differentiable. Version within a set at a point, but with full pullback.
The pullback of a differentiable vector field by a C^n
function with 2 ≤ n
is
differentiable. Version within a set at a point, but with full pullback.
The pullback of a differentiable vector field by a C^n
function with 2 ≤ n
is
differentiable. Version on a set, but with full pullback
The pullback of a differentiable vector field by a C^n
function with 2 ≤ n
is
differentiable. Version at a point.
The pullback of a differentiable vector field by a C^n
function with 2 ≤ n
is
differentiable.
The pullback of a C^m
vector field by a C^n
function with invertible derivative and
m + 1 ≤ n
is C^m
.
Version within a set at a point.
The pullback of a C^m
vector field by a C^n
function with invertible derivative and
with m + 1 ≤ n
is C^m
.
Version within a set at a point.
The pullback of a C^m
vector field by a C^n
function with invertible derivative and
with m + 1 ≤ n
is C^m
.
Version within a set at a point.
The pullback of a C^m
vector field by a C^n
function with invertible derivative and
with m + 1 ≤ n
is C^m
.
Version within a set at a point.
The pullback of a C^m
vector field by a C^n
function with invertible derivative and
with m + 1 ≤ n
is C^m
.
Version within a set at a point.
The pullback of a C^m
vector field by a C^n
function with invertible derivative and
with m + 1 ≤ n
is C^m
.
Version within a set at a point, with a set used for the pullback possibly larger.
The pullback of a C^m
vector field by a C^n
function with invertible derivative and
with m + 1 ≤ n
is C^m
.
Version within a set at a point, with a set used for the pullback possibly larger.
The pullback of a C^m
vector field by a C^n
function with invertible derivative and
with m + 1 ≤ n
is C^m
.
Version on a set.
The pullback of a C^m
vector field by a C^n
function with invertible derivative and
with m + 1 ≤ n
is C^m
.
Version within a set at a point, but with full pullback.
The pullback of a C^m
vector field by a C^n
function with invertible derivative and
with m + 1 ≤ n
is C^m
.
Version within a set at a point, but with full pullback.
The pullback of a C^m
vector field by a C^n
function with invertible derivative and
with m + 1 ≤ n
is C^m
.
Version within a set at a point, but with full pullback.
The pullback of a C^m
vector field by a C^n
function with invertible derivative and
with m + 1 ≤ n
is C^m
.
Version within a set at a point, but with full pullback.
The pullback of a C^m
vector field by a C^n
function with invertible derivative and
with m + 1 ≤ n
is C^m
.
Version on a set, but with full pullback
The pullback of a C^m
vector field by a C^n
function with invertible derivative and
with m + 1 ≤ n
is C^m
.
Version at a point.
The pullback of a C^m
vector field by a C^n
function with invertible derivative and
with m + 1 ≤ n
is C^m
.
The Lie bracket of vector fields in manifolds #
The Lie bracket of two vector fields in a manifold, within a set.
Equations
- One or more equations did not get rendered due to their size.
Instances For
The Lie bracket of two vector fields in a manifold.
Equations
- VectorField.mlieBracket I V W x₀ = VectorField.mlieBracketWithin I V W Set.univ x₀
Instances For
Variant of mlieBracketWithin_congr_set
where one requires the sets to coincide only in
the complement of a point.
Variant of mlieBracketWithin_eventually_congr_set
where one requires the sets to coincide only
in the complement of a point.
If vector fields coincide on a neighborhood of a point within a set, then the Lie brackets also coincide on a neighborhood of this point within this set. Version where one considers the Lie bracket within a subset.
Version of mlieBracketWithin_congr
in which one assumes that the point belongs to the
given set.