Interaction in the dark sector

Abstract

It may well happen that the two main components of the dark sector of the Universe, dark matter and dark energy, do not evolve separately but interact nongravitationally with one another. However, given our current lack of knowledge on the microscopic nature of these two components there is no clear theoretical path to determine their interaction. Yet, over the years, phenomenological interaction terms have been proposed on mathematical simplicity and heuristic arguments. In this paper, based on the likely evolution of the ratio between the energy densities of these dark components, we lay down reasonable criteria to obtain phenomenological, useful, expressions of the said term independent of any gravity theory. We illustrate this with different proposals which seem compatible with the known evolution of the Universe at the background level. Likewise, we show that two possible degeneracies with noninteracting models are only apparent as they can be readily broken at the background level. Further, we analyze some interaction terms that appear in the literature. PACS numbers:PACS: 98.80.-k, 95.35.+d, 95.36.+x

AIC and BIC for cosmological interacting scenarios

“…[34] that an interaction proportional to Hρ x could be consistent with the second law of thermodynamics if the energy transfer is from DE to DM, also, in Ref. [35] it was shown that interactions proportional to H (ρ m + ρ x ) or Hρ m can arise by imposing simple thermodynamic arguments based on the evolution of the ratio ρ m /ρ x . For interactions proportional to ρ m , ρ x or a linear combination of both, we note from Eqs.…”

Study of non-canonical scalar field model using various parametrizations of dark energy equation of state

“…The dynamical nature of dark energy also introduces a new cosmological problem, namely, "coincidence" problem [26]. One alternative to the coincidence problem are coupled dark energy models where DE interchanges energy with the dark matter (DM) by means of a coupling term [27][28][29][30][31][32]. Though a number of theoretical models have been proposed, none of them provides a satisfactory solution to all the problems.…”

Interactive mixture of inhomogeneous dark fluids driven by dark energy: a dynamical system analysis

“…In [46], the authors define the ratio between CDM and DE energy densities ρ m /ρ e in a FLRW homogeneous model. For an interacting term proportional to the DE energy density, they show that the ratio is positive defined, and decreases from infinity monotonously as the universes expands.…”