Parametrized Post-Friedmann Framework for Interacting Dark Energy

Abstract

Dark energy might directly interact with cold dark matter. However, in such a scenario, an early-time large-scale instability occurs occasionally, which may be due to the incorrect treatment for the pressure perturbation of dark energy as a nonadiabatic fluid. To avoid this nonphysical instability, we establish a new framework to correctly calculate the cosmological perturbations in the interacting dark energy models. Inspired by the well-known parametrized post-Friedmann approach, the condition of the dark energy pressure perturbation is replaced with the relationship between the momentum density of dark energy and that of other components on large scales. By reconciling the perturbation evolutions on the large and small scales, one can complete the perturbation equations system. The large-scale instability can be successfully avoided and the well-behaved density and metric perturbations are obtained within this framework. Our test results show that this new framework works very well and is applicable to all the interacting dark energy models.

5 pages, 2 figures, 1 table; published version

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• Revisit of the interacting holographic dark energy model after Planck 2015
• Neutrinos in the holographic dark energy model: constraints from latest measurements of expansion history and growth of structure
• Distinguishing interacting dark energy from wCDM with CMB, lensing, and baryon acoustic oscillation data
• Probing the interaction between dark energy and dark matter with the parametrized post-Friedmann approach
• Effects of time-varying $\beta$ in SNLS3 on constraining interacting dark energy models
• Revisiting the holographic dark energy in a non-flat universe: alternative model and cosmological parameter constraints
• CMB and matter power spectra with non-linear dark-sector interactions
• Parameter estimation with Sandage-Loeb test
• Reexploration of interacting holographic dark energy model: Cases of interaction term excluding the Hubble parameter