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Diff — Riemannian manifold

Revision #2473 → #3109 · back to history

modifiedRiemannian manifold (informal)8f489a8ac27e
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note`IsRiemannianManifold I M` is the Prop-valued typeclass registering the Riemannian-manifold predicate on a manifold equipped with an emetric structure and a Riemannian bundle on its tangent bundle.`IsRiemannianManifold I M` is Mathlib's Prop-valued predicate registering the Riemannian-manifold structure on a manifold with an emetric structure and a Riemannian bundle on its tangent bundle.
modifiedRiemannian metric (informal)a54850aeefc7
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note`ContMDiffRiemannianMetric IB n F E` is a family of inner products on the fibers of a vector bundle varying `C^n`-smoothly with the base point; applied to the tangent bundle it is exactly a Riemannian metric.`Bundle.ContMDiffRiemannianMetric IB n F E` is a family of inner products on fibers of a vector bundle varying `C^n`-smoothly with the base point; applied to the tangent bundle it is a Riemannian metric.
modifiedLocal isometry (surfaces)c2055187b47b
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noteNo definition of local isometry between Riemannian manifolds/surfaces exists in Mathlib; only the metric-space `Isometry` predicate is available.No dedicated local-isometry notion for surfaces or Riemannian manifolds exists in Mathlib; only the metric-space `Isometry` predicate is available.
modifiedIntrinsic/extrinsic propertya713aeb65d6a
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noteMathlib has no notion of intrinsic vs extrinsic property of a surface.Mathlib does not formalize the intrinsic-vs-extrinsic distinction for surface properties.
modifiedRiemannian metric and Riemannian manifolde5873192f9b0
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noteAnchor tightened to point to the definitional sentence.Verified: `Bundle.RiemannianMetric E` is a family of inner products on the fibers of a vector bundle; combined with `IsRiemannianManifold`, it packages the Riemannian-manifold definition.
note_annotation`Bundle.RiemannianMetric E` gives a family of inner products on the fibers of a vector bundle (and `IsRiemannianManifold` packages the manifold-level assertion).
modifiedContinuous/smooth Riemannian metric31459bcceb44
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note`IsContinuousRiemannianBundle` and `IsContMDiffRiemannianBundle` express, respectively, that the inner product on fibers varies continuously / `C^n`-smoothly with the base point.`IsContinuousRiemannianBundle` and `IsContMDiffRiemannianBundle` express, respectively, continuous and `C^n`-smooth variation of the fiberwise inner product with the base point.
modifiedMusical isomorphism7d805eedbdd5
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noteThe pointwise `InnerProductSpace.toDual` gives the fiberwise flat isomorphism of a Hilbert space with its dual, but the bundle-level musical isomorphism between the tangent and cotangent bundles is not built in Mathlib.`InnerProductSpace.toDual` gives the pointwise flat isomorphism of a Hilbert space with its dual, but the bundle-level musical isomorphism between the tangent and cotangent bundles is not built in Mathlib.
modifiedIsometry944442fb5605
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noteAnchor changed to the primary definitional sentence; the previous snippet 'a diffeomorphism' was too generic.Verified: Mathlib's `Isometry` for (pseudo)emetric spaces subsumes the induced-distance case, but there is no dedicated Riemannian-isometry predicate preserving the metric tensor.
note_annotationMathlib's `Isometry` for (pseudo)emetric spaces applies at the level of the induced distance, but there is no dedicated `RiemannianIsometry` preserving the smooth structure and the metric tensor.
modifiedRiemannian volume formc4194010724b
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noteThe Riemannian volume form on an oriented Riemannian manifold is not defined in Mathlib; only the pointwise `Orientation.volumeForm` on a single inner product space exists.The Riemannian volume form on an oriented Riemannian manifold is not defined in Mathlib; only pointwise `Orientation.volumeForm` on a single inner product space exists.
modifiedEuclidean metricbf6af90d7432
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note`riemannianMetricVectorSpace F` is the canonical Riemannian metric on an inner product space given by its inner product on each tangent space, and `EuclideanSpace` is the standard inner-product model.`riemannianMetricVectorSpace F` is the canonical Riemannian metric on an inner product space given by its inner product on each tangent space, matching the Euclidean metric on `EuclideanSpace`.
modifiedRiemannian submanifolddbd786d7968d
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noteAnchor sharpened to the defining phrase.Verified: Riemannian submanifolds and induced metrics are absent from Mathlib.
note_annotationRiemannian submanifolds and the induced metric are not formalized.
modifiedFlat torusc8404234c778
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noteAnchor tightened to the naming phrase.Verified: the flat torus as a Riemannian manifold is not present in Mathlib.
note_annotationThe flat torus as a Riemannian manifold is not present in Mathlib.
modifiedPositive combinations of metricsedcae84901d7
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noteAnchor moved to the conclusion of the proposition.Verified: no lemma stating that positive linear combinations of Riemannian metrics remain Riemannian is in Mathlib.
note_annotationNo lemma stating that positive linear combinations of Riemannian metrics remain Riemannian is in Mathlib.
modifiedExistence of Riemannian metric40ba7cadcc2f
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noteMathlib only constructs the canonical Riemannian metric on inner product spaces; the general existence result for arbitrary smooth manifolds (via partitions of unity) is not there.Only the canonical metric on inner product spaces (`riemannianMetricVectorSpace`) is in Mathlib; the general existence result via partitions of unity is not.
modifiedAdmissible curve and lengthb7b2cc5ecf22
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note`Manifold.pathELength` gives the length integral of a `C^1` path in a manifold whose tangent spaces have an `ENorm`; piecewise-smooth admissible curves are subsumed as `C^1` paths.`Manifold.pathELength` computes the length integral of a `C^1` path in a manifold whose tangent spaces carry an `ENorm`; piecewise-smooth admissible curves are subsumed.
modifiedRiemannian distance is a metric6a1a9fe3536b
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note`EMetricSpace.ofRiemannianMetric` builds an emetric space structure whose topology agrees with the manifold's, using `riemannianEDist`; positivity/triangle inequality are proved but only an `ℝ≥0∞`-valued distance is provided.`EMetricSpace.ofRiemannianMetric` produces an emetric-space structure whose topology matches the manifold's, using `riemannianEDist`; the ℝ-valued distance version is not there.
modifiedCompactness iff finite diameter (complete)f00e371f344e
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noteAnchor sharpened from the generic 'If' to the actual proposition text.Verified: the Riemannian 'complete ∧ finite diameter ↔ compact' statement (invoking Hopf–Rinow) is not in Mathlib.
note_annotationThe Riemannian statement 'complete ∧ finite diameter ↔ compact' (invoking Hopf–Rinow) is not in Mathlib.
modifiedAffine connection3a218351b067
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note`CovariantDerivative I F V` is a bundled Koszul connection on a vector bundle; taking `V = TangentSpace I` recovers an affine connection on a manifold.`CovariantDerivative I F V` is Mathlib's bundled Koszul connection on a vector bundle; taking `V = TangentSpace I` recovers an affine connection on a manifold.
modifiedTorsion-free connection240091057396
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noteMathlib defines `CovariantDerivative.torsion` on the tangent bundle and characterizes torsion-freeness via `torsion_eq_zero_iff` (⇔ `∇_X Y - ∇_Y X = [X,Y]`).Mathlib defines `CovariantDerivative.torsion` on the tangent bundle and characterizes torsion-freeness via `torsion_eq_zero_iff` (⇔ `∇_X Y − ∇_Y X = [X,Y]`).
modifiedExistence and uniqueness of geodesicsf88ba9f8e0b4
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noteThe local existence and uniqueness of geodesics is not in Mathlib.Local existence and uniqueness of geodesics is not in Mathlib.
modifiedHopf–Rinow theorem495aa58e4b6f
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noteAnchor moved from the generic 'Let' to the theorem's characterizing sentence.Verified: the Hopf–Rinow theorem is not in Mathlib.
note_annotationThe Hopf–Rinow theorem is not in Mathlib.
modifiedInduced norm from Riemannian metric31c58ce06b92
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mathlib.declBundle.instNormedAddCommGroupBundle.RiemannianMetric.toCore
mathlib.match_kindexactspecial_case
noteUnder `[RiemannianBundle E]`, Mathlib installs a `NormedAddCommGroup (E b)` and `InnerProductSpace ℝ (E b)` on each fiber via `RiemannianMetric.toCore`, giving the induced norm on tangent spaces.`Bundle.RiemannianMetric.toCore` yields an `InnerProductSpace.Core` on each fiber, from which anonymous scoped `NormedAddCommGroup` and `InnerProductSpace` instances on `E b` are derived (the previously cited `Bundle.instNormedAddCommGroup` name does not exist).
addedMetric tensor66691c547769
addedAcceleration of a curve3d5f408004a5
addedSectional curvaturef1eec7715a1c
addedScalar curvature4aee58e5e103
addedIsometric Riemannian manifolds6cc35528c91a