Abstract
In recent years, some studies have drawn attention to the lack of large-angle correlations in the observed cosmic microwave background (CMB) temperature anisotropies with respect to that predicted within the standard $\Lambda$CDM model. Lately, it has been argued that such a lack of correlations could be explained in the framework of the so-called $R_h=ct$ model without inflation. The aim of this work is to study whether there is a mechanism to generate, through a quantum field theory, the primordial power spectrum presented by these authors. Specifically, we consider two different scenarios: first, we assume a scalar field dominating the early Universe in the $R_h=ct$ cosmological model, and second, we deal with the possibility of adding an early inflationary phase to the mentioned model. During the analysis of the consistency between the predicted and observed amplitudes of the CMB temperature anisotropies in both scenarios, we run into deep issues which indicate that it is not clear how to characterize the primordial quantum perturbations within the $R_h=ct$ model.
Highlights
In addition to solve the horizon and flatness problems of the standard Big Bang model, inflation generates a nearly scale invariant power spectrum for density perturbations, which has been exquisitely tested with observations of the cosmic microwave background (CMB) angular spectrum [1,2,3,4,5,6].Recently, a series of theoretical and observational motivations exposed in [17,18,19] finished merging into what today is known as the Rh = ct model [20]
For these modes, the epoch dominated by the scalar field φ should last up until the decoupling epoch in order to the primordial spectrum obtained can have a consistent amplitude with the corresponding observed in the temperature anisotropies of the CMB
Some studies have drawn attention to the lack of large-angle correlations in the observed CMB temperature anisotropies with respect to that predicted within the standard CDM model
Summary
Even the authors argue that the mentioned horizon problem could be solved in the framework of this model without an inflationary epoch at the beginning of the Universe [29]. They hold that the Universe can be described by a FLRW cosmology, where the cosmic fluid filling the Universe satisfies, at all times, the overall equation of state ρ + 3P = 0, where ρ and P are the total energy density and pressure of the cosmic fluid, respectively.
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