Kavli Affiliate: David N. Spergel
| First 5 Authors: Gregory Gabadadze, David N. Spergel, Giorgi Tukhashvili, ,
| Summary:
We study inflation in a recently proposed gravitational effective field
theory describing the trace anomaly. The theory requires an additional scalar
which is massless in the early universe. This scalar — referenced as an
anomalyon — couples to the familiar matter and radiation through the gauge
field trace anomaly. We derive a class of cosmological solutions that deviate
from the standard inflationary ones only slightly, in spite of the fact that
the anomalyon has a sizable time dependent background. On the other hand, the
scalar cosmological perturbations in this theory are different from the
conventional inflationary perturbations. The inflaton and anomalyon
perturbations mix, and one of the diagonal combinations gives the standard
nearly scale-invariant adiabatic spectrum, while the other combination has a
blue power spectrum at short distance scales. We argue that this blue spectrum
can lead to the formation of primordial black holes (PBHs) at distance scales
much shorter than the ones tested in CMB observations. The resulting PBHs can
be heavy enough to survive to the present day universe. For natural values of
the parameters involved the PBHs would constitute only a tiny fraction of the
dark matter, but with fine-tunings perhaps all of dark matter could be
accounted by them. We also show that the theory predicts primordial
gravitational waves which are almost identical to the standard inflationary
ones.
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