Observational signatures of pre-inflationary and lower-dimensional
  effective gravity
  Several alternative ways to quantize gravitational interactions seem to
indicate that gravity at short distances is effectively two-dimensional. If
this were true, and the energy scale at which the dimensional transition occurs
is of the order of the inflationary one, it is reasonable to investigate
eventual signatures in the primordial perturbation spectra. In this paper we
look at this possibility by assuming that the inflationary era was preceded by
an effectively two-dimensional evolution of the Universe. We model the
transition with a mode matching and we show that, in this case, no
observational signatures are expected in the tensor and scalar power spectra
nor in their ratio. We also show that assuming modified dispersion relations
before the matching between two sets of four-dimensional modes leads to similar
results.
