Gravitational Wave During Slowly Evolving

Abstract

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.

5 pages, 1 eps figure, v3: a calculation bug is corrected, the results and the presentation are improved, but the conclusion is unchanged

Cited by in corpus (5)

• Non-linear Realizations of Conformal Symmetry and Effective Field Theory for the Pseudo-Conformal Universe
• Primordial cosmic fluctuations for variable gravity
• The slow expansion with nonminimal derivative coupling and its conformal dual
• Conformal invariant cosmological perturbations via the covariant approach
• Non-singular Bounce from a Phase transition