Gravity Waves Seeded by Turbulence and Magnetic Fields From a First Order Phase Transition With Non-Renormalizable Electroweak Vacua

TL;DR

This paper investigates how non-renormalizable operators in the standard model can lead to first-order phase transitions in the early universe, producing gravitational waves with specific spectra depending on bubble dynamics.

Contribution

It analyzes the impact of friction on bubble expansion velocities and the resulting gravitational wave spectra in models with higher-dimensional operators.

Findings

Gravity waves from bubble collisions are affected by bubble wall velocities.

A phase transition with certain operators is unlikely to produce strong signals.

Deflagration scenarios could produce observable gravitational wave spectra.

Abstract

It is widely believed that the standard model is a low energy effective theory which may have higher dimensional non-renormalizable operators. The existence of these new operators can lead to interesting dynamics for the evolution of the universe, including the appearance of new vacuum states. If the universe today exists in a false vacuum, there will be a non-zero probability to tunnel to the true vacuum state of the universe. Should this transition occur elsewhere in the universe, bubbles of true vacuum will nucleate and expand outwards. Bubbles that nucleate in the hot dense plasma of the early universe will feel a friction from the plasma that acts against the expansion of the bubble, until the bubble eventually reaches a steady state expansion. Unlike many bubble formation scenarios where the bubble wall velocity rapidly approaches the speed of light, friction from the hot primordial plasma can cause the expanding bubble wall to reach a terminal velocity while gravity waves are free to propagate through the hot dense plasma at the speed of light. We analyze the effects of friction on the spectrum of gravity waves caused by bubble collisions. We find that a phase transition in a model with $\phi^6$ and $\phi^8$ operators that proceeds via a detonation in the hot plasma of the early universe is unlikely. In the case of a deflagration, the gravity wave spectrum is small and would likely require a post-LISA experiment such as the Big Bang Observer, but is in principle, observable.