Matter Perturbations in Scaling Cosmology

Understand

A suitable nonlinear interaction between dark matter with an energy density $\rho_{M}$ and dark energy with an energy density $\rho_{X}$ is known to give rise to a non-canonical scaling $\rho_{M} \propto \rho_{X}a^{-\xi}$ where $\xi$ is a parameter which generally deviates from $\xi =3$.

• Here we present a covariant generalization of this class of models and investigate the corresponding perturbation dynamics.
• The resulting matter power spectrum for the special case of a time-varying Lambda model is compared with data from the SDSS DR9 catalogue.
• We find a best-fit value of $\xi = 3.25$ which corresponds to a decay of dark matter into the cosmological term.