Gravitational Wave Production by Collisions: More Bubbles

TL;DR

This paper reexamines gravitational wave spectra from bubble collisions during phase transitions, revealing a slower high-frequency fall-off and implications for detection with space-based interferometers.

Contribution

It provides new numerical results showing a different high-frequency spectrum fall-off and a dependence of peak frequency on bubble wall velocity, refining previous models.

Findings

Spectrum rises as f^3.0 at low frequencies

Spectrum falls as f^-1.0 at high frequencies

Impacts detection prospects for space-based interferometers

Abstract

We reexamine the production of gravitational waves by bubble collisions during a first-order phase transition. The spectrum of the gravitational radiation is determined by numerical simulations using the "envelope approximation". We find that the spectrum rises as f^3.0 for small frequencies and decreases as f^-1.0 for high frequencies. Thus, the fall-off at high frequencies is significantly slower than previously stated in the literature. This result has direct impact on detection prospects for gravity waves originating from a strong first-order electroweak phase transition at space-based interferometers, such as LISA or BBO. In addition, we observe a slight dependence of the peak frequency on the bubble wall velocity.