# Cosmic backgrounds of relic gravitons and their absolute normalization

@article{Giovannini2014CosmicBO, title={Cosmic backgrounds of relic gravitons and their absolute normalization}, author={Massimo Giovannini}, journal={Classical and Quantum Gravity}, year={2014}, volume={31} }

Provided the consistency relations are not violated, the recent BICEP2 observations pin down the absolute normalization, the spectral slope and the maximal frequency of the cosmic graviton background produced during inflation. The properly normalized spectra are hereby computed from the lowest frequencies (of the order of the present Hubble rate) up to the highest frequency range in the GHz region. Deviations from the conventional paradigm cannot be excluded and are examined by allowing for…

## 11 Citations

The refractive index of relic gravitons

- Physics
- 2015

The dynamical evolution of the refractive index of the tensor modes of the geometry produces a specific class of power spectra characterized by a blue (i.e. slightly increasing) slope which is…

Hypermagnetic knots and gravitational radiation at intermediate frequencies

- Physics
- 2017

The maximally gyrotropic configurations of the hypermagnetic field at the electroweak epoch can induce a stochastic background of relic gravitational waves with comoving frequencies ranging from the…

Post-inflationary thermal histories and the refractive index of relic gravitons

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- 2018

We investigate the impact of the post-inflationary thermal histories on the cosmic graviton spectrum caused by the inflationary variation of their refractive index. Depending on the frequency band,…

The propagating speed of relic gravitational waves and their refractive index during inflation

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- 2018

If the refractive index of the tensor modes increases during a conventional inflationary stage of expansion the relic graviton spectrum is tilted towards high frequencies. Two apparently diverse…

Precision cosmology and the stiff-amplified gravitational-wave background from inflation: NANOGrav, Advanced LIGO-Virgo and the Hubble tension

- PhysicsJournal of Cosmology and Astroparticle Physics
- 2021

The recent NANOGrav finding of a common-spectrum process has invited interpretations as possible evidence of a primordial stochastic gravitational-wave background (SGWB) stronger than predicted by…

High frequency background gravitational waves from spontaneous emission of gravitons by hydrogen and helium

- Physics
- 2021

A direct consequence of quantization of gravity would be the existence of gravitons. Therefore, spontaneous transition of an atom from an excited state to a lower-lying energy state accompanied with…

Electromagnetic response to high-frequency gravitational waves having additional polarization states: distinguishing and probing tensor-mode, vector-mode and scalar-mode gravitons

- PhysicsThe European Physical Journal C
- 2020

Gravitational waves (GWs) from extra dimensions, very early universe, and some high-energy astrophysical processes might have at most six polarization states: tensor- and nontensor-mode gravitons.…

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