The slow expansion with nonminimal derivative coupling and its conformal
  dual
  We show that the primordial gravitational wave with scale-invariant spectrum
might emerge from a nearly Minkowski space, in which the gravity is
asymptotic-past free. We illustrate it with a model, in which the derivative of
background scalar field nonminimally couples to gravity. We also show that
since here the tensor perturbation is dominated by its growing mode,
mathematically our slowly expanding background is conformally dual to the
matter contraction, but there is no the anisotropy problem.
