Gravitational waves from first order cosmological phase transitions in the Sound Shell Model

By M. Hindmarsh, Mulham Hijazi. Journal of Cosmology and Astroparticle Physics, 2019

187 citations recorded by the source corpus.

We calculate gravitational wave power spectra from first order early Universe phase transitions using the Sound Shell Model. The model predicts that the power spectrum depends on the mean bubble separation, the phase transition strength, the phase boundary speed, with the overall frequency scale set by the nucleation temperature. There is also a dependence on the time evolution of the bubble nucleation rate. The gravitational wave peak power and frequency are in good agreement with published numerical simulations, where bubbles are nucleated simultaneously. Agreement is particularly good for detonations, but the total power for deflagrations is predicted higher than numerical simulations show, indicating refinement of the model of the transfer of energy to the fluid is needed for accurate computations. We show how the time-dependence of the bubble nucleation rate affects the shape of the power spectrum: an exponentially rising nucleation rate produces higher amplitude gravitational waves at a longer wavelength than simultaneous nucleation. We present an improved fit for the predicted gravitational wave power spectrum in the form of a double broken power law, where the two breaks in the slope happen at wavenumber corresponding to the mean bubble separation and the thickness of the fluid shell surrounding the expanding bubbles, which in turn is related to the difference of the phase boundary speed from the speed of sound.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics, Statistical and Nonlinear Physics

View Paper: https://www.semanticscholar.org/paper/fcbdece8db2d44cb009696e8cdad89b10594c23c

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Citations in the corpus

Model-independent energy budget of cosmological first-order phase transitions—A sound argument to go beyond the bag model (2020, methodology): “Finally, the bag constant can be mapped using the trace of the energy momentum tensor (θ = gμνT ) which has been advocated in [21,23,24,29] Dθ = De− 3Dp , αθ = Dθ 3ws(T+) .”
Challenges and opportunities of gravitational-wave searches at MHz to GHz frequencies (2020, background): “The strength parameter is roughly, but not precisely, one quarter of the latent heat divided by the thermal energy (see Hindmarsh and Hijazi 2019 for a more precise definition) at the nucleation temperature, and also follows from knowing f ðT ;/Þ.”
Theoretical uncertainties for cosmological first-order phase transitions (2020, background): “For strongly supercooled transitions, the second derivative of the tunnelling action can modify the relation between the tunneling action and the inverse time scale of the transition [91, 92], however we will not consider this dynamical effect further, as our focus is on quantum field theoretic unce”
Updated predictions for gravitational waves produced in a strongly supercooled phase transition (2020, background): “However, the direct detection of gravitational waves (GWs) by the LIGO and Virgo Collaborations [5] has recently stimulated widespread interest in the potential observability of GWs [6] produced in such a transition [7–47].”