Bubble dynamics in a QCD-like phase diagram

Abstract: A line of first-order phase transitions is conjectured in the phase diagram of Quantum Chromodynamics at non-zero baryon density. If this is the case, numerical simulations of neutron star mergers suggest that various regions of the stars may cross this line multiple times. This results in the nucleation of bubbles of the preferred phase, which subsequently expand and collide. The resulting gravitational wave spectrum is highly sensitively to the velocity of the bubble walls. We use holography to perform the first microscopic simulation of bubble dynamics in a theory that qualitatively mirrors the expected phase diagram of Quantum Chromodynamics. We determine the wall velocity in the metastable regions and we compare it to theoretical estimates. We discuss implications for gravitational wave production.