Scale-invariant perturbations from NEC violation: A new variant of
  Galilean Genesis
  We propose a novel branch of the Galilean Genesis scenario as an alternative
to inflation, in which the universe starts expanding from Minkowski in the
asymptotic past with a gross violation of the null energy condition (NEC). This
variant, described by several functions and parameters within the Horndeski
scalar-tensor theory, shares the same background dynamics with the existing
Genesis models, but the nature of primordial quantum fluctuations is quite
distinct. In some cases, tensor perturbations grow on superhorizon scales. The
tensor power spectrum can be red, blue, or scale invariant, depending on the
model, while scalar perturbations are nearly scale invariant. This is in sharp
contrast to typical NEC-violating cosmologies, in which a blue tensor tilt is
generated. Though the primordial tensor and scalar spectra are both nearly
scale invariant as in the inflationary scenario, the consistency relation in
our variant of Galilean Genesis is non-standard.
