Dissipative Effects as New Observables for Cosmological Phase Transitions

We show that dissipative effects during cosmological first order phase transitions lead to a frequency-dependent suppression for the usually dominant gravitational wave production from sound waves, through an analytical modelling of the source based on the sound shell model. This damping effect is more pronounced for high frequencies or small scales, and modifies the spectral shape and possibly the peak frequency. These modifications can be used to reveal more information about the underlying particle interactions, serving as a way of breaking the parameter degeneracy that plagues particle physics studies based on the perfect fluid approximation.