Stochastic backgrounds of relic gravitons, T$\Lambda$CDM paradigm and the stiff ages

Abstract

Absent any indirect tests on the thermal history of the Universe prior to the formation of light nuclear elements, it is legitimate to investigate situations where, before nucleosyntheis, the sound speed of the plasma was larger than $c/\sqrt{3}$, at most equalling the speed of light $c$. In this plausible extension of the current cosmological paradigm, hereby dubbed Tensor-$\Lambda$CDM (i.e. T$\Lambda$CDM) scenario, high-frequency gravitons are copiously produced. Without conflicting with the bounds on the tensor to scalar ratio stemming from the combined analysis of the three standard cosmological data sets (i.e. cosmic microwave background anisotropies, large-scale structure and supenovae), the spectral energy density of the relic gravitons in the T$\Lambda$CDM scenario can be potentially observable by wide-band interferometers (in their advanced version) operating in a frequency window which ranges between few Hz and few kHz.

15 pages, 8 figures

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Cited by in corpus (46)

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• Ability of LIGO and LISA to probe the equation of state of the early Universe
• Unification of inflation and dark energy {\it à la} quintessential inflation
• Thermal history of the plasma and high-frequency gravitons
• A class of quintessential inflation models with parameter space consistent with BICEP2
• Ricci Reheating
• Stochastic backgrounds of relic gravitons: a theoretical appraisal
• Primordial backgrounds of relic gravitons
• Reheating in quintessential inflation via gravitational production of heavy massive particles: A detailed analysis
• A review of Quintessential Inflation
• Inconsistency of an inflationary sector coupled only to Einstein gravity
• Precision cosmology and the stiff-amplified gravitational-wave background from inflation: NANOGrav, Advanced LIGO-Virgo and the Hubble tension
• Detecting relic gravitational waves in the CMB: Optimal parameters and their constraints
• Hanbury Brown-Twiss interferometry and second-order correlations of inflaton quanta
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• Secondary graviton spectra and waterfall-like fields
• Detecting relic gravitational waves in the CMB: Comparison of different methods
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• Detecting Relic Gravitational Waves in the CMB: Comparison of Planck and Ground-based Experiments
• Post-inflationary thermal histories and the refractive index of relic gravitons
• Cosmic backgrounds of relic gravitons and their absolute normalization
• Inflation, space-borne interferometers and the expansion history of the Universe
• The symmetries of inflationary magnetogenesis and the plasma initial conditions
• The first observations of wide-band interferometers and the spectra of relic gravitons
• Relic gravitons from stiff curvature perturbations
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• Detection of relic gravitational waves in the CMB: Prospects for CMBPol mission
• Compressible hydromagnetic nonlinearities in the predecoupling plasma
• Graviton creation from the CMB in large scale magnetic fields
• The refractive index of the relic gravitons and the nHz band
• The spectrum of Gravitational Waves, their overproduction in quintessential inflation and its influence in the reheating temperature
• Hypermagnetic knots and gravitational radiation at intermediate frequencies
• Relic gravitons and pulsar timing arrays: a theoretical viewpoint
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• Multimodality in the Search for New Physics in Pulsar Timing Data and the Case of Kination-amplified Gravitational-wave Background from Inflation
• Multiplicity distributions in gravitational and strong interactions
• Secondary graviton spectra, second-order correlations and Bose-Einstein enhancement
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• Flat spectra of cosmic gravitons in the nHz and audio bands
• Gravitational particle production of superheavy massive particles in Quintessential Inflation: A numerical analysis
• SageNet: Fast Neural Network Emulation of the Stiff-amplified Gravitational Waves from Inflation
• Relic gravitons at intermediate frequencies and the expansion history of the Universe
• Viscous absorption of ultra-high-frequency gravitons