Speaker
Description
We perform the first 3-dimensional numerical simulations of cosmological first-order phase transitions that consistently incorporate both the evolution of background metric and the evolution of the strength of phase transitions throughout the entire phase transition. We find that, in addition to reducing bubble separations via an effectively increased nucleation rate, cosmic expansion intriguingly induces a non-linear growth in the gravitational wave energy, ultimately leading to a significant enhancement of the gravitational wave signals for deflagration modes. In the most extreme case, the enhancement reaches a factor of 7. Owing to the different approaches used to estimate the sound wave lifetime, this enhancement is more pronounced for initially weak transitions than for initially intermediate transitions. Our result highlights the challenge and importance of accurately modelling slow phase transitions with cosmic expansion.