Unphysical properties in a class of interacting dark energy models

Abstract

Models with non-gravitational interactions between the dark matter and dark energy components are an alternative to the standard cosmological scenario. These models are characterized by an interaction term, and a frequently used parameterization is $Q=3\xi H{\rho }_x$, where $H$ is the Hubble parameter and ${\rho }_x$ is the dark energy density. Although current observations support such a model for negative values of the interaction parameter $\xi$, we show here that this interval of values of $\xi$ leads the model to predict a violation of the Weak Energy Condition (WEC) for the dark matter density, regardless of the value of the equation-of-state parameter of the dark energy component. This violation is accompanied by unphysical instabilities of matter perturbations.

17 pages, 7 figures. Accepted for publication in the EPJC

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• Hint of dark matter-dark energy interaction in DESI DR2 and current cosmological dataset?
• Non-Parametric Analysis for the Dark Matter Density Evolution
• Interacting dark sector with quadratic coupling: theoretical and observational viability
• Stage IV CMB forecasts for warm inflation
• New tests of dark sector interactions from the full-shape galaxy power spectrum
• Crunching, Bouncing, and Cyclical Cosmologies from Dark Sector Interactions