The Yamabe problem and conformal scalar curvature
The declarations the status of Tau Ceti's roadmap names, and the other results named in the modules where only this status names declarations, or in folders below the areas where only it names 2 or more, as Tau Ceti has them at commit ace60277.
TheoremScalar curvature of a conformal metric#
In dimension n ≠ 2, let u be a positive
function such that ĝ = u ^ (4 / (n - 2)) g is a smooth metric. Then the scalar curvature of ĝ
is Scal_ĝ = u ^ (-(n + 2) / (n - 2)) L_g u, where L_g is the conformal Laplacian of g.
Such a u is automatically smooth.
TauCeti.Yamabe.scalarCurvature_rescale_eq_rpow_mul_conformalLaplacian.{u_1, u_2, u_3} {E : Type u_1}
[NormedAddCommGroup E] [NormedSpace ℝ E] [FiniteDimensional ℝ E] {H : Type u_2}
[TopologicalSpace H] {I : ModelWithCorners ℝ E H} {M : Type u_3} [TopologicalSpace M]
[ChartedSpace H M] [T2Space M] [IsManifold I (↑⊤) M]
(g : Bundle.ContMDiffRiemannianMetric I (↑⊤) E fun x => TangentSpace I x)
(hn : Module.finrank ℝ E ≠ 2) {u : M → ℝ} (hu_pos : ∀ (x : M), 0 < u x)
{hf : ContMDiff I (modelWithCornersSelf ℝ ℝ) ↑⊤ fun x => u x ^ (4 / (↑(Module.finrank ℝ E) - 2))}
{hf_pos : ∀ (x : M), 0 < u x ^ (4 / (↑(Module.finrank ℝ E) - 2))} (x : M) :
(g.rescale (fun x => u x ^ (4 / (↑(Module.finrank ℝ E) - 2))) hf hf_pos).scalarCurvature x =
u x ^ (-(↑(Module.finrank ℝ E) + 2) / (↑(Module.finrank ℝ E) - 2)) *
TauCeti.Yamabe.conformalLaplacian I u x
Lean
Formalized in Tau Ceti as TauCeti.Yamabe.scalarCurvature_rescale_eq_rpow_mul_conformalLaplacian.
Sources
- Tau Ceti documentation:
TauCeti.Yamabe.scalarCurvature_rescale_eq_rpow_mul_conformalLaplacian - Source of
TauCeti.Yamabe.scalarCurvature_rescale_eq_rpow_mul_conformalLaplacianin TauCeti/Analysis/PDE/Yamabe/ConformalLaplacian.lean - Tau Ceti roadmap status: The Yamabe problem and conformal scalar curvature
Uses 3 · Used by 2
TheoremThe Yamabe equation#
In dimension n ≠ 2, let u be a positive function such that
ĝ = u ^ (4 / (n - 2)) g is a smooth metric. Then ĝ has scalar curvature c at a point exactly
when u solves the Yamabe equation L_g u = c u ^ (pₙ - 1) there, where pₙ = 2 n / (n - 2).
TauCeti.Yamabe.scalarCurvature_rescale_eq_iff_conformalLaplacian_eq.{u_1, u_2, u_3} {E : Type u_1}
[NormedAddCommGroup E] [NormedSpace ℝ E] [FiniteDimensional ℝ E] {H : Type u_2}
[TopologicalSpace H] {I : ModelWithCorners ℝ E H} {M : Type u_3} [TopologicalSpace M]
[ChartedSpace H M] [T2Space M] [IsManifold I (↑⊤) M]
(g : Bundle.ContMDiffRiemannianMetric I (↑⊤) E fun x => TangentSpace I x)
(hn : Module.finrank ℝ E ≠ 2) {u : M → ℝ} (hu_pos : ∀ (x : M), 0 < u x)
{hf : ContMDiff I (modelWithCornersSelf ℝ ℝ) ↑⊤ fun x => u x ^ (4 / (↑(Module.finrank ℝ E) - 2))}
{hf_pos : ∀ (x : M), 0 < u x ^ (4 / (↑(Module.finrank ℝ E) - 2))} (c : ℝ) (x : M) :
(g.rescale (fun x => u x ^ (4 / (↑(Module.finrank ℝ E) - 2))) hf hf_pos).scalarCurvature x = c ↔
TauCeti.Yamabe.conformalLaplacian I u x =
c * u x ^ (TauCeti.Yamabe.criticalExponent (Module.finrank ℝ E) - 1)
Lean
Formalized in Tau Ceti as TauCeti.Yamabe.scalarCurvature_rescale_eq_iff_conformalLaplacian_eq.
Sources
Uses 3
TheoremVolume-normalized total scalar curvature of a conformal metric#
On a compact manifold of
dimension n ≠ 2, let u be a positive function such that ĝ = u ^ (4 / (n - 2)) g is a smooth
metric, and let pₙ = 2 n / (n - 2). Then
(∫ Scal_ĝ dV_ĝ) / Vol(ĝ) ^ (2 / pₙ) = (∫ u L_g u dV_g) / (∫ u ^ pₙ dV_g) ^ (2 / pₙ),
where L_g is the conformal Laplacian of g.
TauCeti.Yamabe.integral_scalarCurvature_rescale_div_riemannianTotalVolume_rpow.{u_1, u_2, u_3}
{E : Type u_1} [NormedAddCommGroup E] [NormedSpace ℝ E] [FiniteDimensional ℝ E] {H : Type u_2}
[TopologicalSpace H] {I : ModelWithCorners ℝ E H} {M : Type u_3} [TopologicalSpace M]
[ChartedSpace H M] [T2Space M] [IsManifold I (↑⊤) M] [LindelofSpace M] [CompactSpace M]
(g : Bundle.ContMDiffRiemannianMetric I (↑⊤) E fun x => TangentSpace I x)
(hn : Module.finrank ℝ E ≠ 2) {u : M → ℝ} (hu_pos : ∀ (x : M), 0 < u x)
{hf : ContMDiff I (modelWithCornersSelf ℝ ℝ) ↑⊤ fun x => u x ^ (4 / (↑(Module.finrank ℝ E) - 2))}
{hf_pos : ∀ (x : M), 0 < u x ^ (4 / (↑(Module.finrank ℝ E) - 2))} :
(∫ (x :
TauCeti.WithMetric
(g.rescale (fun x => u x ^ (4 / (↑(Module.finrank ℝ E) - 2))) hf hf_pos)),
(g.rescale (fun x => u x ^ (4 / (↑(Module.finrank ℝ E) - 2))) hf hf_pos).scalarCurvature
x.ofWithMetric ∂TauCeti.riemannianVolume I
(TauCeti.WithMetric
(g.rescale (fun x => u x ^ (4 / (↑(Module.finrank ℝ E) - 2))) hf hf_pos))) /
TauCeti.riemannianTotalVolume I
(TauCeti.WithMetric
(g.rescale (fun x => u x ^ (4 / (↑(Module.finrank ℝ E) - 2))) hf hf_pos)) ^
(2 / TauCeti.Yamabe.criticalExponent (Module.finrank ℝ E)) =
(∫ (x : TauCeti.WithMetric g),
u x.ofWithMetric *
TauCeti.Yamabe.conformalLaplacian I u
x.ofWithMetric ∂TauCeti.riemannianVolume I (TauCeti.WithMetric g)) /
(∫ (x : TauCeti.WithMetric g),
u x.ofWithMetric ^
TauCeti.Yamabe.criticalExponent
(Module.finrank ℝ E) ∂TauCeti.riemannianVolume I (TauCeti.WithMetric g)) ^
(2 / TauCeti.Yamabe.criticalExponent (Module.finrank ℝ E))
Lean
Formalized in Tau Ceti as TauCeti.Yamabe.integral_scalarCurvature_rescale_div_riemannianTotalVolume_rpow.
Sources
- Tau Ceti documentation:
TauCeti.Yamabe.integral_scalarCurvature_rescale_div_riemannianTotalVolume_rpow - Source of
TauCeti.Yamabe.integral_scalarCurvature_rescale_div_riemannianTotalVolume_rpowin TauCeti/Analysis/PDE/Yamabe/TotalScalarCurvature.lean - Tau Ceti roadmap status: The Yamabe problem and conformal scalar curvature
Uses 5
TheoremWeyl tensor under conformal change#
Away from dimension 2, the fully covariant Weyl
tensor of a conformally rescaled smooth metric f g is f times that of g:
W^(f g)(u, v, w, z) = f W^g(u, v, w, z). Equivalently, the Weyl tensor of type (1, 3) is
conformally invariant.
Bundle.ContMDiffRiemannianMetric.weylTensor_leviCivitaConnection_rescale.{u_1, u_2, u_3}
{E : Type u_1} [NormedAddCommGroup E] [NormedSpace ℝ E] [FiniteDimensional ℝ E] {H : Type u_2}
[TopologicalSpace H] {I : ModelWithCorners ℝ E H} {M : Type u_3} [TopologicalSpace M]
[ChartedSpace H M] [T2Space M] [IsManifold I (↑⊤) M]
(g : Bundle.ContMDiffRiemannianMetric I (↑⊤) E fun x => TangentSpace I x) {f : M → ℝ}
(hf : ContMDiff I (modelWithCornersSelf ℝ ℝ) (↑⊤) f) (hf_pos : ∀ (x : M), 0 < f x)
(hn : Module.finrank ℝ E ≠ 2) (x : M) (u v w z : TangentSpace I x) :
(((((CovariantDerivative.leviCivitaConnection I M).weylTensor x) u) v) w) z =
f x * (((((CovariantDerivative.leviCivitaConnection I M).weylTensor x) u) v) w) z
Lean
Formalized in Tau Ceti as Bundle.ContMDiffRiemannianMetric.weylTensor_leviCivitaConnection_rescale.
Sources
- Tau Ceti documentation:
Bundle.ContMDiffRiemannianMetric.weylTensor_leviCivitaConnection_rescale - Source of
Bundle.ContMDiffRiemannianMetric.weylTensor_leviCivitaConnection_rescalein TauCeti/Geometry/Manifold/VectorBundle/CovariantDerivative/Curvature/Conformal/Basic.lean - Tau Ceti roadmap status: The Yamabe problem and conformal scalar curvature
Uses 2 · Used by 2
TheoremLocal conformal flatness forces the Weyl tensor to vanish#
Away from dimension 2, the
Weyl tensor of a locally conformally flat metric vanishes at every point. This is the easy half of
the Weyl–Schouten theorem.
Bundle.ContMDiffRiemannianMetric.IsLocallyConformallyFlat.weylTensor_eq_zero.{u_1, u_2, u_3}
{E : Type u_1} [NormedAddCommGroup E] [NormedSpace ℝ E] [FiniteDimensional ℝ E] {H : Type u_2}
[TopologicalSpace H] {I : ModelWithCorners ℝ E H} {M : Type u_3} [TopologicalSpace M]
[ChartedSpace H M] [T2Space M] [IsManifold I (↑⊤) M]
{g : Bundle.ContMDiffRiemannianMetric I (↑⊤) E fun x => TangentSpace I x}
(hg : g.IsLocallyConformallyFlat) (hn : Module.finrank ℝ E ≠ 2) (x : M) :
(CovariantDerivative.leviCivitaConnection I M).weylTensor x = 0
Lean
Formalized in Tau Ceti as Bundle.ContMDiffRiemannianMetric.IsLocallyConformallyFlat.weylTensor_eq_zero.
Sources
- Tau Ceti documentation:
Bundle.ContMDiffRiemannianMetric.IsLocallyConformallyFlat.weylTensor_eq_zero - Source of
Bundle.ContMDiffRiemannianMetric.IsLocallyConformallyFlat.weylTensor_eq_zeroin TauCeti/Geometry/Manifold/VectorBundle/CovariantDerivative/Curvature/ConformallyFlat/Basic.lean - Tau Ceti roadmap status: The Yamabe problem and conformal scalar curvature
Uses 3 · Used by 1
TheoremThe bubbles attain the Yamabe constant of the sphere#
in dimension n > 2, for Lebesgue
measure, aₙ ∫ ‖dU_{t,b}‖² = Y(Sⁿ) (∫ U_{t,b} ^ pₙ) ^ (2 / pₙ). This is the equality case of the
sharp Euclidean Sobolev inequality.
TauCeti.Yamabe.conformalCoefficient_mul_integral_norm_fderiv_bubble_sq_eq_sphereYamabeConstant.{u_1}
{E : Type u_1} [NormedAddCommGroup E] [InnerProductSpace ℝ E] [FiniteDimensional ℝ E]
[MeasurableSpace E] [BorelSpace E] (hn : 2 < Module.finrank ℝ E) {t : ℝ} (ht : 0 < t) (b : E) :
TauCeti.Yamabe.conformalCoefficient (Module.finrank ℝ E) *
∫ (x : E), ‖fderiv ℝ (TauCeti.Yamabe.bubble t b) x‖ ^ 2 =
TauCeti.Yamabe.sphereYamabeConstant (Module.finrank ℝ E) *
(∫ (x : E),
TauCeti.Yamabe.bubble t b x ^ TauCeti.Yamabe.criticalExponent (Module.finrank ℝ E)) ^
(2 / TauCeti.Yamabe.criticalExponent (Module.finrank ℝ E))
Lean
Formalized in Tau Ceti as TauCeti.Yamabe.conformalCoefficient_mul_integral_norm_fderiv_bubble_sq_eq_sphereYamabeConstant.
Sources
- Tau Ceti documentation:
TauCeti.Yamabe.conformalCoefficient_mul_integral_norm_fderiv_bubble_sq_eq_sphereYamabeConstant - Source of
TauCeti.Yamabe.conformalCoefficient_mul_integral_norm_fderiv_bubble_sq_eq_sphereYamabeConstantin TauCeti/Analysis/PDE/Yamabe/Bubble/SobolevQuotient.lean - Tau Ceti roadmap status: The Yamabe problem and conformal scalar curvature
Uses 1
TheoremThe area of the unit round sphere#
|Sⁿ| = 2 π ^ ((n + 1) / 2) / Γ((n + 1) / 2).
TauCeti.roundSphereVolume_eq_two_mul_pi_rpow_div_Gamma (n : ℕ) :
TauCeti.roundSphereVolume n = 2 * Real.pi ^ ((↑n + 1) / 2) / Real.Gamma ((↑n + 1) / 2)
Lean
Formalized in Tau Ceti as TauCeti.roundSphereVolume_eq_two_mul_pi_rpow_div_Gamma.
Sources
Used by 1
DefinitionTauCeti.Yamabe.conformalLaplacian#
The conformal Laplacian L_g u = aₙ Δ⁺_g u + Scal_g u of a function u on a smooth
Riemannian manifold of dimension n, where aₙ = 4 (n - 1) / (n - 2), Δ⁺_g = -Δ_g is the
nonnegative Laplacian and Scal_g is the scalar curvature.
TauCeti.Yamabe.conformalLaplacian.{u_1, u_2, u_3} {E : Type u_1} [NormedAddCommGroup E]
[NormedSpace ℝ E] [FiniteDimensional ℝ E] {H : Type u_2} [TopologicalSpace H]
(I : ModelWithCorners ℝ E H) {M : Type u_3} [TopologicalSpace M] [ChartedSpace H M] [T2Space M]
[IsManifold I (↑⊤) M] [Bundle.RiemannianBundle fun x => TangentSpace I x]
[IsContMDiffRiemannianBundle I (↑⊤) E fun x => TangentSpace I x] (u : M → ℝ) (x : M) : ℝ
Uses 1 · Used by 3
DefinitionBundle.ContMDiffRiemannianMetric.IsLocallyConformallyFlat#
A smooth Riemannian metric g is locally conformally flat if every point x has a
neighbourhood on which a conformal rescaling f g, by a smooth positive function f, is flat:
the curvature tensor of the Levi-Civita connection of f g vanishes at every point near x.
Bundle.ContMDiffRiemannianMetric.IsLocallyConformallyFlat.{u_1, u_2, u_3} {E : Type u_1}
[NormedAddCommGroup E] [NormedSpace ℝ E] [FiniteDimensional ℝ E] {H : Type u_2}
[TopologicalSpace H] {I : ModelWithCorners ℝ E H} {M : Type u_3} [TopologicalSpace M]
[ChartedSpace H M] [T2Space M] [IsManifold I (↑⊤) M]
(g : Bundle.ContMDiffRiemannianMetric I (↑⊤) E fun x => TangentSpace I x) : Prop
Lean
Formalized in Tau Ceti as Bundle.ContMDiffRiemannianMetric.IsLocallyConformallyFlat.
Sources
- Tau Ceti documentation:
Bundle.ContMDiffRiemannianMetric.IsLocallyConformallyFlat - Source of
Bundle.ContMDiffRiemannianMetric.IsLocallyConformallyFlatin TauCeti/Geometry/Manifold/VectorBundle/CovariantDerivative/Curvature/ConformallyFlat/Basic.lean - Tau Ceti roadmap status: The Yamabe problem and conformal scalar curvature
Uses 1 · Used by 2
DefinitionCovariantDerivative.cottonTensor#
The Cotton tensor C(u, v, w) = (∇_w P)(u, v) - (∇_v P)(u, w) of a smooth connection, where
P is the Schouten tensor and ∇P is CovariantDerivative.derivSchoutenTensor. The usual
formula on vector fields holds for a smooth metric (see
CovariantDerivative.cottonTensor_apply_of_mdifferentiableAt); otherwise ∇P, and hence the
Cotton tensor, may be 0.
CovariantDerivative.cottonTensor.{u_1, u_2, u_3} {E : Type u_1} [NormedAddCommGroup E]
[NormedSpace ℝ E] [FiniteDimensional ℝ E] {H : Type u_2} [TopologicalSpace H]
{I : ModelWithCorners ℝ E H} {M : Type u_3} [TopologicalSpace M] [ChartedSpace H M] [T2Space M]
[IsManifold I (↑⊤) M] [Bundle.RiemannianBundle (TangentSpace I)]
(cov : CovariantDerivative I E (TangentSpace I)) [cov.ContMDiffCovariantDerivative ↑⊤] (x : M) :
TangentSpace I x →ₗ[ℝ] TangentSpace I x →ₗ[ℝ] TangentSpace I x →ₗ[ℝ] ℝ
Used by 1
TheoremWeyl–Schouten in dimension three, on a model space#
An arbitrary smooth Riemannian metric is locally conformally flat if and only if its Cotton tensor vanishes.
Bundle.ContMDiffRiemannianMetric.isLocallyConformallyFlat_iff_cottonTensor_eq_zero_model_space.{u_1}
{E : Type u_1} [NormedAddCommGroup E] [NormedSpace ℝ E] [FiniteDimensional ℝ E]
(g :
Bundle.ContMDiffRiemannianMetric (modelWithCornersSelf ℝ E) (↑⊤) E fun x =>
TangentSpace (modelWithCornersSelf ℝ E) x)
(hn : Module.finrank ℝ E = 3) :
g.IsLocallyConformallyFlat ↔
∀ (x : E),
(CovariantDerivative.leviCivitaConnection (modelWithCornersSelf ℝ E) E).cottonTensor x = 0
Lean
Formalized in Tau Ceti as Bundle.ContMDiffRiemannianMetric.isLocallyConformallyFlat_iff_cottonTensor_eq_zero_model_space.
Other forms
Weyl–Schouten in dimension at least four, on a model space. Formalized in Tau Ceti as Bundle.ContMDiffRiemannianMetric.isLocallyConformallyFlat_iff_weylTensor_eq_zero_model_space.
Bundle.ContMDiffRiemannianMetric.isLocallyConformallyFlat_iff_weylTensor_eq_zero_model_space.{u_1}
{E : Type u_1} [NormedAddCommGroup E] [NormedSpace ℝ E] [FiniteDimensional ℝ E]
(g :
Bundle.ContMDiffRiemannianMetric (modelWithCornersSelf ℝ E) (↑⊤) E fun x =>
TangentSpace (modelWithCornersSelf ℝ E) x)
(hn : 4 ≤ Module.finrank ℝ E) :
g.IsLocallyConformallyFlat ↔
∀ (x : E),
(CovariantDerivative.leviCivitaConnection (modelWithCornersSelf ℝ E) E).weylTensor x = 0
Sources
- Tau Ceti documentation:
Bundle.ContMDiffRiemannianMetric.isLocallyConformallyFlat_iff_cottonTensor_eq_zero_model_space - Source of
Bundle.ContMDiffRiemannianMetric.isLocallyConformallyFlat_iff_cottonTensor_eq_zero_model_spacein TauCeti/Geometry/Manifold/VectorBundle/CovariantDerivative/Curvature/ConformallyFlat/ModelSpace.lean
Uses 9
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