Speaker
Description
In extensions of the Standard Model, symmetry breaking or confinement of new gauge groups can give rise to first order phase transitions. The phase transition creates expanding bubbles of the stable phase that grow and merge until they fill the entire universe, leaving behind pressure and velocity perturbations. This process creates gravitational waves. The Laser Interferometer Space Antenna (LISA) is expected to be able to detect the gravitational waves from a first-order electroweak-scale phase transition.
The validity of the picture depends on the bubbles being stable to aspherical perturbations: an instability would lead to crumpling of the phase boundary and greatly reduce the amplitude of the gravitational waves. So far, the stability of the bubbles has only been calculated assuming planar symmetry and constant pressure and velocity away from the phase boundary. The results of this approximation predict that the bubbles should not grow as large as they do in simulations.
We study for the first time the hydrodynamic stability of spherical bubbles with the correct radial profiles of pressure and velocity. We map out the complex frequencies of the perturbations and show how the stability is modified by the more physical geometry and boundary conditions.