Riemannian vector bundles #
Given a vector bundle over a manifold whose fibers are all endowed with a scalar product, we say that this bundle is Riemannian if the scalar product depends smoothly on the base point.
We introduce a typeclass [IsContMDiffRiemannianBundle IB n F E] registering this property. Under this assumption, we show that the scalar product of two smooth maps into the same fibers of the bundle is a smooth function.
If the fibers of a bundle E have a preexisting topology (like the tangent bundle), one cannot assume additionally [∀ b, InnerProductSpace ℝ (E b)] as this would create diamonds. Instead, use [RiemannianBundle E], which endows the fibers with a scalar product while ensuring that there is no diamond (for this, the Bundle scope should be open). We provide a constructor for [RiemannianBundle E] from a smooth family of metrics, which registers automatically [IsContMDiffRiemannianBundle IB n F E].
The following code block is the standard way to say "Let E be a smooth vector bundle equipped with a C^n Riemannian structure over a C^n manifold B":
variable {EB : Type*} [NormedAddCommGroup EB] [NormedSpace ℝ EB] {HB : Type*} [TopologicalSpace HB] {IB : ModelWithCorners ℝ EB HB} {n : WithTop ℕ∞} {B : Type*} [TopologicalSpace B] [ChartedSpace HB B] {F : Type*} [NormedAddCommGroup F] [NormedSpace ℝ F] {E : B → Type*} [TopologicalSpace (TotalSpace F E)] [∀ x, NormedAddCommGroup (E x)] [∀ x, InnerProductSpace ℝ (E x)] [FiberBundle F E] [VectorBundle ℝ F E] [IsManifold IB n B] [ContMDiffVectorBundle n F E IB] [IsContMDiffRiemannianBundle IB n F E] Consider a real vector bundle in which each fiber is endowed with a scalar product. We that the bundle is Riemannian if the scalar product depends smoothly on the base point. This assumption is spelled IsContMDiffRiemannianBundle IB n F E where IB is the model space of the base, n is the smoothness, F is the model fiber, and E : B → Type* is the bundle.
Instances
A trivial vector bundle, in which the model fiber has a scalar product, is a Riemannian bundle.
Given two smooth maps into the same fibers of a Riemannian bundle, their scalar product is smooth.
Given two smooth maps into the same fibers of a Riemannian bundle, their scalar product is smooth.
Given two smooth maps into the same fibers of a Riemannian bundle, their scalar product is smooth.
Given two smooth maps into the same fibers of a Riemannian bundle, their scalar product is smooth.
Given two differentiable maps into the same fibers of a Riemannian bundle, their scalar product is differentiable.
Given two differentiable maps into the same fibers of a Riemannian bundle, their scalar product is differentiable.
Given two differentiable maps into the same fibers of a Riemannian bundle, their scalar product is differentiable.
Given two differentiable maps into the same fibers of a Riemannian bundle, their scalar product is differentiable.
A family of inner product space structures on the fibers of a fiber bundle, defining the same topology as the already existing one, and varying continuously with the base point. See also ContinuousRiemannianMetric for a continuous version.
This structure is used through RiemannianBundle for typeclass inference, to register the inner product space structure on the fibers without creating diamonds.
The scalar product along the fibers of the bundle.
Instances For
A smooth Riemannian metric defines in particular a continuous Riemannian metric.
Equations
- g.toContinuousRiemannianMetric = { inner := g.inner, symm := ⋯, pos := ⋯, isVonNBounded := ⋯, continuous := ⋯ }
Instances For
A smooth Riemannian metric defines in particular a Riemannian metric.