Timescape cosmology with radiation fluid

Understand

The timescape cosmology represents a potentially viable alternative to the standard homogeneous cosmology, without the need for dark energy.

• Although average cosmic evolution in the timescape scenario only differs substantially from that of Friedmann-Lemaitre model at relatively late epochs when the contribution from the energy density of radiation is negligible, a full solution of the Buchert equations to incorporate radiation is necessary to smoothly match parameters to the epoch of photon decoupling and to obtain constraints from cosmic microwave background data.
• Here we extend the matter-dominated solution found in earlier work to include radiation, providing series solutions at early times and an efficient numerical integration strategy for generating the complete solution.
• The numerical solution is used to directly calculate the scale of the sound horizon at decoupling, and at the baryon drag epoch.