Hyperbolic -space,
denoted
,
is, up to isometry, the simply
connected Riemannian manifold of dimension
having constant sectional
curvature
.
It is a complete metric space. Rescaling
its metric by a factor
gives sectional curvature
. The cases
and
are called the hyperbolic
plane and hyperbolic 3-space, respectively.
Standard models of hyperbolic space include ball, upper half-space, projective, and hyperboloid models. Although their coordinate descriptions differ, the models are mutually isometric. In dimension 2, familiar examples are the Poincaré hyperbolic disk and the Klein-Beltrami model. Hyperbolic space is also a homogeneous space and a symmetric space.