Relic gravitons from stiff curvature perturbations

2020/06/04 by Massimo Giovannini
Mathematics · Physics and Astronomy · #Black Holes and Theoretical Physics #Classical mechanics #Cosmology and Gravitation Theories #Curvature #Effective action #Galaxies: Formation, Evolution, Phenomena #Geometry #Gravitation #Graviton #Mathematical physics #Mathematics #Physics #astro-ph.CO #gr-qc #hep-ph #hep-th

paper · pdf · doi:10.1016/j.physletb.2020.135801

11 pages

arxiv created 2020/06/04 · openalex publication_date 2020/09/22 · arxiv updated 2020/10/28 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

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.

Citations

• The cosmological gravitational wave background from primordial density perturbations
• Hybrid inflation along waterfall trajectories
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• How long before the end of inflation were observable perturbations produced?
• Simple inflationary quintessential model. II. Power law potentials