Primordial Tensor Perturbation in Double Inflationary Scenario with a Break

Abstract

We study the primordial tensor perturbation produced from the double inflationary scenario with an intermediate break stage. Because of the transitions, the power spectrum deviates from the vacuum one and there will appear oscillatory behavior. In the case of a scalar-type curvature perturbation, it is known that the amplitude of these oscillations may be enhanced to result in the power spectrum larger than the one for the vacuum case. One might expect the similar enhancement for the tensor perturbation as well. Unfortunately, it is found that when the equation of state (EOS) parameter $w=p/\rho$ of the break stage is a constant with $w>-1/3$, the amplitude of oscillations is never large enough to enhance the power spectrum. On the contrary, the power spectrum is found to be suppressed even on those scales that leave the horizon at the first inflationary stage and remain superhorizon throughout the entire stage. We identify the cause of this suppression with the correction terms in additional to the leading order constant solution on superhorizon scales. We argue that our result is general in the sense that any intermediate break stage during inflation cannot yield an enhancement of the tensor spectrum as long as the Hubble expansion rate is non-increasing in time.

20 pages, 4 figures, Latex (version 2: one paragraph added in the conclusion section and two references added)

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• Towards a reliable calculation of relic radiation from primordial gravitational waves
• Enhanced Curvature Perturbation and Primordial Black Hole Formation in Two-stage Inflation with a break
• Inflationary Potential as seen from Different Angles: Model Compatibility from Multiple CMB Missions
• One-loop infrared rescattering by enhanced scalar fluctuations during inflation
• Primordial black holes from a curvaton scenario with strongly non-Gaussian perturbations
• Tracking the Multifield Dynamics with Cosmological Data: A Monte Carlo approach
• Very-High-Frequency Gravitational Waves from Multi-Monodromy Inflation