Relic gravitons from stiff curvature perturbations

Abstract

The tensor modes reentering the Hubble radius when the plasma is dominated by a stiff fluid lead to a spectral energy density whose blue slope depends on the total post-inflationary sound speed. This result gets however corrected by a secondary (gauge-dependent) term coming from the curvature inhomogeneities that reenter all along the same stage of expansion. In comparison with the first-order result, the secondary contribution is shown to be always suppressed inside the sound horizon and its effect on the total spectral energy density of the relic gravitons is therefore negligible for all phenomenological purposes. It is also suggested that the effective anisotropic stress of the curvature inhomogeneities can be obtained from the functional derivative of the second-order action of curvature inhomogeneities with respect to the background metric.

11 pages

References in corpus (9)

• The cosmological gravitational wave background from primordial density perturbations
• Hybrid inflation along waterfall trajectories
• Minimal Higgs inflation with an $R^2$ term in Palatini gravity
• Primordial backgrounds of relic gravitons
• Warm Quintessential Inflation
• Simple inflationary quintessential model II: Power law potentials
• Secondary graviton spectra and waterfall-like fields
• The Peebles -- Vilenkin quintessential inflation model revisited
• Instant preheating in a scale invariant two measures theory

Cited by in corpus (1)

• Inflation, space-borne interferometers and the expansion history of the Universe