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 whereGis a manifold on the model with cornersI.LieGroup I G: a Lie multiplicative group whereGis a manifold on the model with cornersI.ContMDiffInv₀: typeclass forC^nmanifolds with0andInvsuch that inversion isC^nmap at each non-zero point. This includes complete normed fields and (multiplicative) Lie groups.
Main results #
ContMDiff.inv,ContMDiff.divand variants: point-wise inversion and division of mapsM → GisC^n.ContMDiff.inv₀and variants: ifContMDiffInv₀ I n N, point-wise inversion ofC^nmapsf : M → NisC^nat all points at whichfdoesn't vanish.ContMDiff.div₀and variants: if alsoContMDiffMul I n N(i.e.,Nis 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/UnitsOfNormedAlgebrashows 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^naway 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.