  The ekpyrotic slow contraction or the slow expansion might be responsible for
the adiabatical production of the nearly scale invariant curvature
perturbation. However, the tensor perturbation generated is generally strongly
blue, which implies that it is negligible on large scale. Thus it has been
still thought that the detection of primordial tensor perturbation will rule
out the relevant models. Here, we will show a counterexample. We will
illustrate that in a model of the slow evolution, due to the rapid change of
the gravitational coupling, both the curvature perturbation and the tensor
perturbation can be nearly scale invariant. The resulting ratio of the tensor
to scalar is in a regime which can be detected by the coming or planned
experiments. We argue that the result is similar to that of inflation is
because the background evolution given here is actually conformally equivalent
to the inflationary background.

High Energy Physics - Theory