Induced gravitational waves as a probe of thermal history of the universe

Abstract

The scalar perturbation induced gravitational waves are a probe of the primordial density perturbation spectrum on small scales. In this paper, we show that they can also probe the thermal history of the universe. We assume the universe underwent a stage with a constant equation of state parameter $w$, followed by the radiation-dominated stage of the conventional big bang universe. We find that the infrared slope of the power spectrum of the induced stochastic gravitational wave background for decelerating cosmologies is related to the equation of state of the universe. Furthermore, the induced gravitational wave spectrum has in general a broken power-law shape around the scale of reheating. Interestingly, below the threshold $w=0$ of the equation of state parameter, the broken power-law presents a peak for a Dirac delta peak in the scalar spectrum. For a finite width peak, the threshold changes to $w=-1/15$ depending on the value of the width. In some cases, such a broken power-law gravitational wave spectrum may degenerate to the spectrum from other sources like phase transitions or global cosmic strings.

References in corpus (18)

• Gravitational Wave Spectrum Induced by Primordial Scalar Perturbations
• Gravitational-wave sensitivity curves
• The cosmological gravitational wave background from primordial density perturbations
• Gravitational Waves from Phase Transitions at the Electroweak Scale and Beyond
• Gravitational wave generation from bubble collisions in first-order phase transitions: an analytic approach
• Theory and Numerics of Gravitational Waves from Preheating after Inflation
• Gravitational Wave Production At The End Of Inflation
• A stochastic background of gravitational waves from hybrid preheating
• Constraints on the induced gravitational wave background from primordial black holes
• Observable Spectra of Induced Gravitational Waves from Inflation
• Gauge Independence of Induced Gravitational Waves
• Unified treatment of cosmological perturbations from super-horizon to small scales
• Resonant multiple peaks in the induced gravitational waves
• The gravitational waves from the first-order phase transition with a dimension-six operator
• Gravitational Waves from Oscillons with Cuspy Potentials
• Thermal History of the Early Universe and Primordial Gravitational Waves from Induced Scalar Perturbations
• Second-order perturbations of cosmological fluids: Relativistic effects of pressure, multi-component, curvature, and rotation
• Observational signatures of the parametric amplification of gravitational waves during reheating after inflation

Cited by in corpus (10)

• Gravitational Waves Induced by Scalar Perturbations with a Lognormal Peak
• The Gravitational-Wave Physics II: Progress
• Primordial black holes and secondary gravitational waves from inflationary model with a non-canonical kinetic term
• Approximate gauge independence of the induced gravitational wave spectrum
• Gravitational waves from dark matter isocurvature
• Primordial Gravitational Waves From Black Hole Evaporation in Standard and Non-Standard Cosmologies
• Primordial black holes and scalar induced gravitational waves from the $E$ model with a Gauss-Bonnet term
• Double-peaked inflation model: Scalar induced gravitational waves and primordial-black-hole suppression from primordial non-Gaussianity
• Primordial Non-Gaussianity from G-inflation
• Scalar induced gravitational waves review