Indications of a late-time interaction in the Dark Sector

Valentina Salvatelli, Najla Said, Marco Bruni, Alessandro Melchiorri, David Wands

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We show that a general late-time interaction between cold dark matter and vacuum energy isfavoured by current cosmological datasets. We characterize the strength of the coupling by a dimensionless parameter qV that is free to take different values in four redshift bins from the primordialepoch up to today. This interacting scenario is in agreement with measurements of cosmic microwavebackground temperature anisotropies from the Planck satellite, supernovae Ia from Union 2.1 andredshift space distortions from a number of surveys, as well as with combinations of these differentdatasets. Our analysis of the 4-bin interaction shows that a non-zero interaction is likely at latetimes. We then focus on the case qV ≠ 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 toΛCDM, 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 qV . For thiscase the null interaction (qV = 0, i.e. ΛCDM) is excluded at 99% C.L.
Original languageEnglish
Article number181301
Number of pages5
JournalPhysical Review Letters
Issue number18
Early online date30 Oct 2014
Publication statusPublished - 31 Oct 2014


  • RCUK
  • STFC
  • ST/K00090X/1
  • ST/L005573/1


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