Lie groups #
A Lie group is a group that is also a C^n
manifold, in which the group operations of
multiplication and inversion are C^n
maps. Regularity of the group multiplication means that
multiplication is a C^n
mapping of the product manifold G
× G
into G
.
Note that, since a manifold here is not second-countable and Hausdorff a Lie group here is not guaranteed to be second-countable (even though it can be proved it is Hausdorff). Note also that Lie groups here are not necessarily finite dimensional.
Main definitions #
LieAddGroup I G
: a Lie additive group whereG
is a manifold on the model with cornersI
.LieGroup I G
: a Lie multiplicative group whereG
is a manifold on the model with cornersI
.ContMDiffInv₀
: typeclass forC^n
manifolds with0
andInv
such that inversion isC^n
map at each non-zero point. This includes complete normed fields and (multiplicative) Lie groups.
Main results #
ContMDiff.inv
,ContMDiff.div
and variants: point-wise inversion and division of mapsM → G
isC^n
.ContMDiff.inv₀
and variants: ifContMDiffInv₀ I n N
, point-wise inversion ofC^n
mapsf : M → N
isC^n
at all points at whichf
doesn't vanish.ContMDiff.div₀
and variants: if alsoContMDiffMul I n N
(i.e.,N
is a Lie group except possibly for smoothness of inversion at0
), similar results hold for point-wise division.instNormedSpaceLieAddGroup
: a normed vector space over a nontrivially normed field is an additive Lie group.Instances/UnitsOfNormedAlgebra
shows that the group of units of a complete normed𝕜
-algebra is a multiplicative Lie group.
Implementation notes #
A priori, a Lie group here is a manifold with corners.
The definition of Lie group cannot require I : ModelWithCorners 𝕜 E E
with the same space as the
model space and as the model vector space, as one might hope, because in the product situation,
the model space is ModelProd E E'
and the model vector space is E × E'
, which are not the same,
so the definition does not apply. Hence the definition should be more general, allowing
I : ModelWithCorners 𝕜 E H
.
An additive Lie group is a group and a C^n
manifold at the same time in which
the addition and negation operations are C^n
.
- compatible {e e' : PartialHomeomorph G H} : e ∈ atlas H G → e' ∈ atlas H G → e.symm.trans e' ∈ contDiffGroupoid n I
- contMDiff_add : ContMDiff (I.prod I) I n fun (p : G × G) => p.1 + p.2
Negation is smooth in an additive Lie group.
Instances
A (multiplicative) Lie group is a group and a C^n
manifold at the same time in which
the multiplication and inverse operations are C^n
.
- compatible {e e' : PartialHomeomorph G H} : e ∈ atlas H G → e' ∈ atlas H G → e.symm.trans e' ∈ contDiffGroupoid n I
- contMDiff_mul : ContMDiff (I.prod I) I n fun (p : G × G) => p.1 * p.2
Inversion is smooth in a Lie group.
Instances
Smoothness of inversion, negation, division and subtraction #
Let f : M → G
be a C^n
function into a Lie group, then f
is point-wise
invertible with smooth inverse f
. If f
and g
are two such functions, the quotient
f / g
(i.e., the point-wise product of f
and the point-wise inverse of g
) is also C^n
.
In a Lie group, inversion is C^n
.
In an additive Lie group, inversion is a smooth map.
Alias of contMDiff_inv
.
In a Lie group, inversion is C^n
.
Alias of contMDiff_neg
.
In an additive Lie group, inversion is a smooth map.
A Lie group is a topological group. This is not an instance for technical reasons, see note [Design choices about smooth algebraic structures].
An additive Lie group is an additive topological group. This is not an instance for technical reasons, see note [Design choices about smooth algebraic structures].
Alias of ContMDiffWithinAt.inv
.
Alias of ContMDiffAt.inv
.
Alias of ContMDiffOn.inv
.
Alias of ContMDiff.inv
.
Alias of ContMDiffWithinAt.neg
.
Alias of ContMDiffAt.neg
.
Alias of ContMDiffOn.neg
.
Alias of ContMDiff.neg
.
Alias of ContMDiffWithinAt.div
.
Alias of ContMDiffAt.div
.
Alias of ContMDiffOn.div
.
Alias of ContMDiff.div
.
Alias of ContMDiffWithinAt.sub
.
Alias of ContMDiffAt.sub
.
Alias of ContMDiffOn.sub
.
Alias of ContMDiff.sub
.
Binary product of Lie groups
Normed spaces are Lie groups #
C^n
manifolds with C^n
inversion away from zero #
Typeclass for C^n
manifolds with 0
and Inv
such that inversion is C^n
at all non-zero
points. (This includes multiplicative Lie groups, but also complete normed semifields.)
Point-wise inversion is C^n
when the function/denominator is non-zero.
A C^n
manifold with 0
and Inv
such that fun x ↦ x⁻¹
is C^n
at all nonzero points.
Any complete normed (semi)field has this property.
- contMDiffAt_inv₀ ⦃x : G⦄ : x ≠ 0 → ContMDiffAt I I n (fun (y : G) => y⁻¹) x
Inversion is
C^n
away from0
.
Instances
Alias of ContMDiffInv₀
.
A C^n
manifold with 0
and Inv
such that fun x ↦ x⁻¹
is C^n
at all nonzero points.
Any complete normed (semi)field has this property.
Equations
Instances For
Alias of contMDiffAt_inv₀
.
In a manifold with C^n
inverse away from 0
, the inverse is continuous away from 0
.
This is not an instance for technical reasons, see
note [Design choices about smooth algebraic structures].
Alias of hasContinuousInv₀_of_hasContMDiffInv₀
.
In a manifold with C^n
inverse away from 0
, the inverse is continuous away from 0
.
This is not an instance for technical reasons, see
note [Design choices about smooth algebraic structures].
Alias of contMDiffOn_inv₀
.
Alias of contMDiffOn_inv₀
.
Alias of ContMDiffWithinAt.inv₀
.
Alias of ContMDiffAt.inv₀
.
Alias of ContMDiffOn.inv₀
.
Alias of ContMDiff.inv₀
.
Point-wise division of C^n
functions #
If [ContMDiffMul I n N]
and [ContMDiffInv₀ I n N]
, point-wise division of C^n
functions f : M → N
is C^n
whenever the denominator is non-zero.
(This includes N
being a completely normed field.)
Alias of ContMDiffWithinAt.div₀
.
Alias of ContMDiffAt.div₀
.
Alias of ContMDiffOn.div₀
.
Alias of ContMDiff.div₀
.