Exact solution to the averaging problem in cosmology

Understand

The exact solution of a two-scale Buchert average of the Einstein equations is derived for an inhomogeneous universe which represents a close approximation to the observed universe.

• The two scales represent voids, and the bubble walls surrounding them within which clusters of galaxies are located.
• As described elsewhere [gr-qc/0702082], apparent cosmic acceleration can be recognised as a consequence of quasilocal gravitational energy gradients between observers in bound systems and the volume average position in freely expanding space.
• With this interpretation, the new solution presented here replaces the Friedmann solutions, in representing the average evolution of a matter-dominated universe without exotic dark energy, while being observationally viable.