Gravitational Fluctuations as an Alternative to Inflation III. Numerical
  Results
  Power spectra play an important role in the theory of inflation, and their
ability to reproduce current observational data to high accuracy is often
considered a triumph of inflation, largely because of a lack of credible
alternatives. In previous work we introduced an alternative picture for the
cosmological power spectra based on the nonperturbative features of the quantum
version of Einstein's gravity, instead of currently popular inflation models
based on scalar fields. The key ingredients in this new picture are the
appearance of a nontrivial gravitational vacuum condensate (directly related to
the observed cosmological constant), and a calculable renormalization group
running of Newton's G on cosmological scales. Results obtained previously were
largely based on a semi-analytical treatment, and often suffered from the
limitations of various approximations and simplifying assumptions. In this
work, we extend and refine our previous calculations by laying out an updated
and extended analysis, which now utilizes a set of suitably modified
state-of-the-art numerical programs (ISiTGR, MGCAMB and MGCLASS) developed for
observational cosmology. As a result, we are able to remove some of the
approximations employed in our previous studies, leading to a number of novel
and detailed physical predictions. These should help in potentially distinguish
the vacuum condensate picture of quantum gravity from that of other models such
as scalar field inflation. Here, besides the matter power spectrum P(k), we
work out in detail predictions for what are referred to as the TT, TE, EE, BB
angular spectra, as well as their closely related lensing spectra. However, the
current limited precision of observational data today (especially on large
angular scales) does not allow us yet to clearly prove or disprove either set
of ideas.
