  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.
