Alphabeta Math

Riemann Curvature and Riemannian Submanifolds

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✓ 55 results · all verified · 53 also independently AI-judged
Every result on this page is machine-checked by a proof checker and read in full and owner-audited; the judge is an additional, independent cross-model AI review of the proofs. The 2 not AI-judged were verified by owner audit (typically over a confirmed judge false positive), not failures.
1 · Prerequisites
Abstract Algebra
Combinatorics
Coxeter Groups
Differential Geometry
Linear Algebra
Measure Theory
Number Theory
Real Analysis
Set Theory
Topology
2 · Logical flowchart

3 · Items

Definition

Curvature of an affine connection

Lemma

Curvature is C-infinity-linear in all three vector fields

Theorem

Curvature is a type (1,3) tensor

Proposition

Curvature is skew in its first two arguments

Proposition

Coordinate formula for the curvature tensor

Definition

Curvature of a vector-bundle connection

Proposition

Vector-bundle curvature is an endomorphism-valued two-form

Theorem

Curvature two-form structure equation

Theorem

Second Bianchi identity for a bundle connection

Proposition

Flat connections have locally path-independent parallel transport on a coordinate ball

Theorem

A flat connection admits local parallel frames

Definition

Riemann curvature four-tensor

Theorem

First Bianchi identity

Theorem

Algebraic symmetries of the Riemann tensor

Theorem

Differential second Bianchi identity

Definition

Sectional curvature

Lemma

Sectional curvature is independent of the basis of the plane

Theorem

Sectional curvatures determine the Riemann tensor

Definition

Constant sectional curvature and space form

Proposition

Curvature tensor of constant sectional curvature

Definition

Ricci curvature

Lemma

Ricci curvature is symmetric and basis independent

Definition

Scalar curvature

Proposition

Scalar curvature is twice the sum of sectional curvatures of orthonormal coordinate planes

Definition

Kulkarni–Nomizu product, trace-free Ricci tensor, and Weyl curvature

Proposition

Ricci decomposition of the Riemann tensor in dimension at least three

Theorem

Contracted second Bianchi identity

Theorem

Schur's lemma for pointwise constant sectional curvature

Theorem

A Riemannian manifold is flat iff it is locally isometric to Euclidean space

Definition

Tangential and normal projections along a Riemannian submanifold

Definition

Induced connection and second fundamental form

Theorem

The induced connection is Levi–Civita

Lemma

The second fundamental form is a symmetric normal-bundle-valued two-tensor

Definition

Normal connection

Definition

Shape operator

Theorem

Weingarten equation and adjointness of the shape operator

Theorem

Gauss equation for a Riemannian submanifold

Theorem

Codazzi equation for a Riemannian submanifold

Theorem

Ricci equation for the normal connection

Definition

Totally geodesic submanifold

Theorem

Equivalent characterizations of a totally geodesic submanifold

Definition

Principal curvatures, Gaussian curvature, and mean curvature of an oriented hypersurface

Proposition

Euclidean hypersurface sectional curvature from principal curvatures

Theorem

Gauss’s Theorema Egregium

Definition

Mean curvature vector

Proposition

First variation of volume for a normal variation

Remark

Mean curvature and minimal submanifolds

False statement

Curvature is obtained by commuting two covariant derivatives without a bracket correction

False statement

Christoffel symbols vanishing at one point implies curvature vanishes there

False statement

Sectional curvature depends on an ordered basis of the plane

False statement

Ricci curvature and scalar curvature determine the full Riemann tensor in every dimension

False statement

The second fundamental form is intrinsic to the abstract Riemannian manifold

False statement

Zero mean curvature implies a submanifold is totally geodesic

Example

The round sphere has positive constant sectional curvature

Example

Euclidean space has zero curvature

Sources