Search results
Results from the WOW.Com Content Network
Riemannian geometry is the branch of differential geometry that studies Riemannian manifolds, defined as smooth manifolds with a Riemannian metric (an inner product on the tangent space at each point that varies smoothly from point to point). This gives, in particular, local notions of angle, length of curves, surface area and volume.
The fundamental theorem of Riemannian geometry states that on any Riemannian manifold (or pseudo-Riemannian manifold) there is a unique affine connection that is torsion-free and metric-compatible, called the Levi-Civita connection or (pseudo-) Riemannian connection of the given metric.
In particular, on a closed Riemannian manifold of negative Ricci curvature, every Killing vector field is identically zero. Since the isometry group of a complete Riemannian manifold is a Lie group whose Lie algebra is naturally identified with the vector space of Killing vector fields, it follows that the isometry group is zero-dimensional. [4]
In mathematics, the soul theorem is a theorem of Riemannian geometry that largely reduces the study of complete manifolds of non-negative sectional curvature to that of the compact case. Jeff Cheeger and Detlef Gromoll proved the theorem in 1972 by generalizing a 1969 result of Gromoll and Wolfgang Meyer.
Let be a smooth manifold and let be a one-parameter family of Riemannian or pseudo-Riemannian metrics. Suppose that it is a differentiable family in the sense that for any smooth coordinate chart, the derivatives v i j = ∂ ∂ t ( ( g t ) i j ) {\displaystyle v_{ij}={\frac {\partial }{\partial t}}{\big (}(g_{t})_{ij}{\big )}} exist and are ...
The limit of a convergent subsequence may be a metric space without any smooth or Riemannian structure. [6] This special case of the metric compactness theorem is significant in the field of Riemannian geometry , as it isolates the purely metric consequences of lower Ricci curvature bounds.
Let be a complete n-dimensional Riemannian manifold whose Ricci curvature satisfies the lower bound ()for a constant .Let be the complete n-dimensional simply connected space of constant sectional curvature (and hence of constant Ricci curvature ()); thus is the n-sphere of radius / if >, or n-dimensional Euclidean space if =, or an appropriately rescaled version of n-dimensional hyperbolic ...
Hopf–Rinow theorem is a set of statements about the geodesic completeness of Riemannian manifolds. It is named after Heinz Hopf and his student Willi Rinow , who published it in 1931. [ 1 ] Stefan Cohn-Vossen extended part of the Hopf–Rinow theorem to the context of certain types of metric spaces .