Echo of interactions in the dark sector

Abstract

We investigate the observational constraints on an interacting vacuum energy scenario with two different neutrino schemes (with and without a sterile neutrino) using the most recent data from CMB temperature and polarization anisotropy, baryon acoustic oscillations (BAO), type Ia supernovae from JLA sample and structure growth inferred from cluster counts. We find that inclusion of the galaxy clusters data with the minimal data combination CMB + BAO + JLA suggests an interaction in the dark sector, implying the decay of dark matter particles into dark energy, since the constraints obtained by including the galaxy clusters data yield a non-null and negative coupling parameter between the dark components at 99% confidence level. We deduce that the current tensions on the parameters H0 and σ8 can be alleviated within the framework of the interacting as well as non-interacting vacuum energy models with sterile neutrinos.PACS numbers: 95.35.+d; 95.36.+x; 14.60.Pq; 98.80.Es

Implications of the possible 21-cm line excess at cosmic dawn on dynamics of interacting dark energy

“…The cosmological 21-cm line is caused by the hyperfine splitting of neutral hydrogen atoms, whose wavelength corresponds to the transition from the triplet state to the singlet state of the electron. We use the brightness temperature T 21 to describe the strength of the global 1 Cosmological models involving non-gravitational interactions between dark energy and dark matter were extensively studied in literatures [50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68]. For instance see [50] for the early study, see [51] for the alleviation of coincidence problem of the current cosmic acceleration, and see [52] for a review.…”

Interacting dark energy model and thermal stability

“…However, to alleviate the Coincidence problem and compatibility with the second law of thermodynamics, Q is normally chosen to be positive [17,[35][36][37]. But recently, from an observational point of view, it has been shown that current observational data can favor the late time interaction in the dark sector with Q < 0 [18,38]. It is well known that the above two fluids can be combined as a single fluid having energy density …”

Exact solutions, finite time singularities and non-singular universe models from a variety of Λ(t) cosmologies

“…One may notice that for δ/β ≪ 1, the equation (28) becomes, H ≃ H 0 exp γβ 2 (t − t 0 ) , and the scale factor becomes double exponential type. However, without imposing any restriction on β and δ, the direct integration of (28) gives the scale factor as 3 One can see the model in equation (176) or equation (3.137) of [35].…”

“…However, the field equations for this theory do not follow from any covariant action. Nevertheless, in the last several years, a series of works towards this direction has been performed with several interesting results [10,11,12,13,14,15,16,17,18,19,20,21,22] and very recently another series of works [23,24,25,26,27,28] showing that the current astronomical data from different independent sources favor the Λ(t) class of models in compared to the concordance ΛCDM cosmology. In view of the observational data, Λ(t) models could be an emerging class of cosmological models, for instance a suitable choice of some models belonging to this class can describe the entire cosmic histroy [16,17,18].…”