Coupling dark energy to dark matter inhomogeneities

Abstract

We propose that dark energy in the form of a scalar field could effectively couple to dark matter inhomogeneities. Through this coupling energy could be transferred to/from the scalar field, which could possibly enter an accelerated regime. Though phenomenological, this scenario is interesting as it provides a natural trigger for the onset of the acceleration of the universe, since dark energy starts driving the expansion of the universe when matter inhomogeneities become sufficiently strong. Here we study a possible realization of this idea by coupling dark energy to dark matter via the linear growth function of matter perturbations. The numerical results show that it is indeed possible to obtain a viable cosmology with the expected series of radiation, matter and dark-energy dominated eras. In particular, the current density of dark energy is given by the value of the coupling parameters rather than by very special initial conditions for the scalar field. In other words, this model - unlike standard models of cosmic late acceleration - does not suffer from the so-called "coincidence problem" and its related fine tuning of initial conditions.

12 pages, 2 figures; revised and expanded discussion of proposed interaction and figures; matches version accepted for publication in Physics of the Dark Universe

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• Cosmological constraints on parametrized interacting dark energy
• Null test for interactions in the dark sector
• An Effective Sign Switching Dark Energy: Lotka-Volterra Model of Two Interacting Fluids
• Observational constraints and predictions of the interacting dark sector with field-fluid mapping
• Cosmological perturbations in the interacting dark sector: Mapping fields and fluids
• CMB and matter power spectra with non-linear dark-sector interactions
• Coupled scalar field cosmology with effects of curvature
• Cosmological constraints on the radiation released during structure formation
• New tests of dark sector interactions from the full-shape galaxy power spectrum