Shape of the acoustic gravitational wave power spectrum from a first order phase transition

Hindmarsh, Mark, Huber, Stephan J, Rummukainen, Kari and Weir, David J (2017) Shape of the acoustic gravitational wave power spectrum from a first order phase transition. Physical Review D, 96 (10). p. 103520. ISSN 2470-0010

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We present results from large-scale numerical simulations of a first order thermal phase transition in the early Universe, in order to explore the shape of the acoustic gravitational wave and the velocity power spectra. We compare the results with the predictions of the recently proposed sound shell model. For the gravitational wave power spectrum, we find that the predicted k−3 behavior, where k is the wave number, emerges clearly for detonations. The power spectra from deflagrations show similar features, but exhibit a steeper high-k decay and an extra feature not accounted for in the model. There are two independent length scales: the mean bubble separation and the thickness of the sound shell around the expanding bubble of the low temperature phase. It is the sound shell thickness which sets the position of the peak of the power spectrum. The low wave number behavior of the velocity power spectrum is consistent with a causal k3, except for the thinnest sound shell, where it is steeper. We present parameters for a simple broken power law fit to the gravitational wave power spectrum for wall speeds well away from the speed of sound where this form can be usefully applied. We examine the prospects for the detection, showing that a LISA-like mission has the sensitivity to detect a gravitational wave signal from sound waves with an RMS fluid velocity of about 0.05c, produced from bubbles with a mean separation of about 10−2 of the Hubble radius. The shape of the gravitational wave power spectrum depends on the bubble wall speed, and it may be possible to estimate the wall speed, and constrain other phase transition parameters, with an accurate measurement of a stochastic gravitational wave background.

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QC Physics
Depositing User: Billy Wichaidit
Date Deposited: 19 Dec 2017 10:04
Last Modified: 19 Dec 2017 10:04

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Project NameSussex Project NumberFunderFunder Ref
Theoretical Particle Physics Consortium Sussex - Royal HollowayG1449STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCILST/L000504/1