Anti-de Sitter space opposite of de Sitter space
Anti-de Sitter space distinguished from de Sitter space
An anti-de Sitter space in general relativity is similar to a de Sitter space, except with the sign of the spacetime curvature changed.  In anti-de Sitter space, in the absence of matter or energy, the curvature of spacelike sections is negative, corresponding to a hyperbolic geometry, and momentarily parallel timelike geodesics eventually intersect.  This corresponds to a negative cosmological constant, where empty space itself has negative energy density but positive pressure, unlike the standard ΛCDM model of our own universe for which observations of distant supernovae indicate a positive cosmological constant corresponding to (asymptotic) de Sitter space.
In an anti-de Sitter space, as in a de Sitter space, the inherent spacetime curvature corresponds to the cosmological constant.
antonym contrary reverse inverse complement