paper

Large-scale (in-) stability Analysis of an Exactly Solved Coupled Dark-Energy Model

arXiv:1808.01669 · doi:10.1103/PhysRevD.98.043517

Abstract

Assuming a non-gravitational interaction amongst the dark fluids of our universe namely, the dark matter and dark energy, we study a specific interaction model in the background of a spatially flat Friedmann-Lemaître-Robertson-Walker geometry. The interaction model, as we found, solves the background evolution in an analytic way when the dark energy takes a constant barotropic equation of state, . In particular, we analyze two separate interaction scenarios, namely, when the dark energy is a fluid other than the vacuum energy (i.e., ) and when it is vacuum energy itself (i.e., ). We found that the interacting model with produces stable perturbation at large scales for with the coupling strength . Both the scenarios have been constrained with the latest astronomical data having distinct origin. The analyses show that a very small interaction with coupling strength is allowed and within 68.3\% confidence-region, is recovered. The analyses further show that a large coupling strength significantly affects the large scale dynamics of the universe while according to the observational data the interaction models are very well consistent with the -cosmology. Furthermore, we observe that for the vacuum interaction scenario, the tension on is not released while for the interacting dark energy scenario with , the tension on seems to be released partially because of the high error bars in . Finally, we close the work with the Bayesian evidence which shows that the CDM cosmology is favored over the two interacting scenarios.

24 pages, many figures; Accepted for publication in Phys. Rev. D

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