Constraints on the interacting vacuumgeodesic CDM scenario
Abstract
We investigate an interacting dark sector scenario in which the vacuum energy is free to interact with cold dark matter (CDM), which itself is assumed to cluster under the sole action of gravity, i.e. it is in freefall (geodesic), as in ΛCDM. The interaction is characterized by a dimensionless coupling q_{V}(z), in general a function of redshift. Aiming to reconstruct the evolution of the coupling, we use cosmic microwave background data from Planck 2015, along with baryon acoustic oscillation, redshift space distortion, and Type Ia supernova measurements to constrain various parametrizations of q_{V}(z). We present the full linear perturbation theory of this interacting scenario and use Monte Carlo Markov Chains (MCMC) sampling to study five different cases: two cases in which we have ΛCDM evolution in the distant past, until a set redshift z_{trans}, below which the interaction switches on and q_{V} is the singlesampled parameter, with z_{trans} fixed at z_{trans} = 3000 and 0.9, respectively; a case where we allow this transition redshift to vary along with q_{V}; a case in which the vacuum energy is zero for z > z_{trans} and then begins to grow once the interaction switches on; and the final case in which we bin q_{V}(z) in four redshift bins to investigate the possibility of a dynamical interaction, reconstructing the redshift evolution of the function using Gaussian processes. We find that, in all cases where the highredshift evolution is not modified, the results are compatible with a vanishing coupling, thus finding no significant deviation from ΛCDM.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 July 2019
 DOI:
 10.1093/mnras/stz1915
 arXiv:
 arXiv:1902.10694
 Bibcode:
 2019MNRAS.488.3423M
 Keywords:

 dark energy;
 dark matter;
 cosmology: theory;
 Astrophysics  Cosmology and Nongalactic Astrophysics
 EPrint:
 17 pages, 14 figures. Version 2 aligns with the published MNRAS article (some model comparison discussion added with respect to version 1)