Speaker
Description
We use a full general relativistic framework to study the self-similar expansion of bubbles of the stable phase in a first order phase transition in the early universe. Self-similarity requires a near-conformal equation of state in both phases, where the ratio between the energy density and pressure of the fluid is constant but different in the two phases. The Israel junction conditions at the interface in the limit of thin shell and large bubble have a structure similar to the energy-momentum conservation in Minkowski spacetime. We find that self-similar detonation and deflagration solutions exist under these assumptions, with peculiar features that discriminate them from the analogous solutions in Minkowski. Both deflagration and detonation solutions describe bubbles with interior spatial negative curvature expanding in a flat Friedmann-Lamaître-Robertson-Walker Universe. The amount of spatial curvature in the interior of the bubble is significantly larger than the naive expectation based on considerations on the energy density perturbation in bubbles expanding on a Minkowski background. We infer that general relativistic effects might have a significant impact in the generation of scalar induced gravitational waves when the bubble size becomes comparable to the cosmological Hubble radius.
