Indications of a Late-Time Interaction in the Dark Sector

Abstract

We show that a general late-time interaction between cold dark matter and vacuum energy is favored by current cosmological data sets. We characterize the strength of the coupling by a dimensionless parameter q(V) that is free to take different values in four redshift bins from the primordial epoch up to today. This interacting scenario is in agreement with measurements of cosmic microwave background temperature anisotropies from the Planck satellite, supernovae Ia from Union 2.1 and redshift space distortions from a number of surveys, as well as with combinations of these different data sets. Our analysis of the 4-bin interaction shows that a nonzero interaction is likely at late times. We then focus on the case q(V)≠0 in a single low-redshift bin, obtaining a nested one parameter extension of the standard ΛCDM model. We study the Bayesian evidence, with respect to ΛCDM, of this late-time interaction model, finding moderate evidence for an interaction starting at z=0.9, dependent upon the prior range chosen for the interaction strength parameter q(V). For this case the null interaction (q(V)=0, i.e., ΛCDM) is excluded at 99% C.L.

Constraining interacting dark energy models with latest cosmological observations

“…Thus the dark energy will be strengthened in the late-time Universe, and then more efficiently drive the cosmic accelerating expansion. Actually, several papers (Salvatelli et al 2014;Sola et al 2015Sola et al , 2016 have provided the first and strong indication of interaction in the dark sector recently.…”

Testing models of vacuum energy interacting with cold dark matter

“…[79], the authors investigated the IΛCDM model with Q ∝ Hρ Λ , where the coupling strength β is set to be redshift dependent and is taken to be different values in four redshift bins in the analysis. They used the Planck 2013 data in combination with the SN Union2.1 sample and the RSD measurements (10 points) to constrain the model and found that the null interaction (β = 0) is excluded at the 99% confidence level.…”

“…The decaying vacuum energy models have been widely studied in the literature; see, e.g., Refs. [73][74][75][76][77][78][79].…”

Braneworld gravity within non-conservative gravitational theory

“…(12) that this model of gravity provides a braneworld scenario with a running effective cosmological "constant". As such this novel aspect is promising for cosmology as it can make feasible the emerging of interactions between dark energy and dark matter [17][18][19][20][21][22][23][24][25][26].…”

“…This equation carries an effective cosmological constant which now becomes a function of the coordinates due to the terms inherited from the modified gravity. This feature is attractive from the cosmological point of view, as a time-dependent cosmological "constant" makes possible a construction of a model of universe where the components of the dark sector are able to interact each other, exchanging energy and momentum [17][18][19][20][21][22][23][24][25][26]. This class of cosmologies usually comes into play as an attempt of addressing the socalled "coincidence problem" [27].…”