Matter Perturbations in Scaling Cosmology

TL;DR

This paper explores a covariant model of dark matter and dark energy interaction that results in a non-canonical scaling, analyzing its perturbations and comparing the matter power spectrum with observational data to find best-fit parameters.

Contribution

It introduces a covariant generalization of nonlinear dark matter-dark energy interaction models and studies their perturbation dynamics and observational implications.

Findings

Best-fit scaling parameter $\xi=3.25$ indicating dark matter decay into dark energy.

Model compatible with $ ext{Lambda}$CDM at 2$\sigma$ confidence level.

Matter power spectrum fits SDSS DR9 data for the proposed model.

Abstract

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. Our results are compatible with the $\Lambda$CDM model at the 2$\sigma$ confidence level.