Inhomogeneous cosmology

Inhomogeneous cosmology usually means the study of structure in the universe by means of exact solutions of Einstein's field equations (i.e. "metrics"). Such models are not homogeneous, but contain enough matter to be possible cosmological models, or models of cosmological structures such as voids or galaxy clusters.

The best known example of such solutions is the Lemaitre-Tolman metric (or LT model). Some other examples are the Szekeres metric, Szafron metric, Stephani metric, Kantowski-Sachs metric, Barnes metric, Kustaanheimo-Qvist metric, Senovilla metric.

(In contrast, perturbation theory, which deals with small perturbations from e.g. a homogeneous metric, only holds as long as the perturabtions are not too large, and N-body simulations use Newtonian gravity which is only a good approximation when speeds are low and gravitational fields are weak.)

References

* Krasinski, A., "Inhomogeneous Cosmological Models", (1997) Cambridge UP, ISBN 0 521 48180 5