http://arxiv.org/abs/1804.08558
Cosmological models where dark matter and dark energy interact with each other are the general ones in compared to the non-interacting models since the later can be obtained setting no interaction in the field equations. The current astronomical data prefer an interaction in the dark regime as shown in a series of investigations by different research teams. However, a drawback of such models which we cannot disagree, is that, no one knows how dark matter and dark energy interact with each other. Thus, there is a complete freedom to choose any specific interaction model by hand but with the ease of astronomical data we can test their viabilities and finally rule out if they do not fit with the expansion history. In this work, allowing an exponential interaction between dark matter and dark energy in a spatially flat Friedmann-Lema\^{\i}tre-Robertson-Walker background, we explore the dynamical history of the universe through the constraints of the free parameters. Our analysis shows that although the interaction is exponential, but the observational data allow a very small coupling strength and can recover the non-interaction scenario within 68\% confidence level. The dark energy state parameter has been found to be very close to the cosmological constant boundary `$-1$’. The overall results show that at the background level, our model cannot be distinguished from the non-interacting $w_{x}$CDM model and the $\Lambda $CDM model while the analysis at the perturbative level clearly show that the model is distinguished from the $w_{x}$CDM model as well as from the $\Lambda $CDM model. The notable point in this work that we would like to highlight is that, the observational data do not seem to allow a strong interaction in the dark sector even if we allow the dark fluids to interact with each other in an exponential manner.
W. Yang, S. Pan and A. Paliathanasis
Tue, 24 Apr 18
18/87
Comments: 11 pages, 6 figures, 2 tables; comments are welcome
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