Reconstructing the dark matter and dark energy interaction scenarios from observations

We consider a class of interacting dark energy models in a flat and nonflat FLRW universe where the interaction is characterized by the modified evolution of the pressureless dark matter as a(-3+delta)(a), a being the FLRW scale factor and delta(a) quantifies the interaction rate. By assuming the most natural and nonsingular parametrization for delta(a) as delta(a) = Sigma(i)delta(i)(1 - a)(i), where delta(i)'s (i = 0, 1, 2, 3, ..) are constants, we reconstruct the expansion history of the universe for three particular choices of the DE sector using different cosmological datasets. Our analyses show that the non-interacting scenario is consistent with the observations while the interaction is not strictly ruled out. We reconstruct in the following way. We start with the first two terms of delta(a) above and constrain delta(0), delta(1). Then we consider up to the second order terms in delta(a) but fix delta(0), delta(1) to their constrained values and constrain delta(2); similarly we constrain delta(3), and finally we constrain (delta(0), delta(1), delta(1), delta(3)) by keeping all of them to be free as a generalized case. Our reconstruction technique shows that the constraints on delta(2) (fixing delta(0) and delta(1)) and delta(3) (fixing delta(0), delta(1) and delta(2)) are almost zero for any interaction model and thus the effective scenario is well described by the linear parametrization delta(a) similar or equal to delta(0) + delta(1)(1 - a). Additionally, a strong negative correlation between delta(0), delta(1) is observed independently of the dark energy fluid and the curvature of our universe. (c) 2019 Elsevier B.V. All rights reserved.