Hydrodynamics of the Cosmological Quark-hadron Transition

Hydrodynamic flow in the neighborhood of a phase interface is studied with particular reference to the cosmological quark-hadron transition. Using a characteristic method, we demonstrate that if the interface moves subsonically, the hydrodynamical energy flux across it cannot, as a matter of principle, be calculated from junction conditions alone. Supply of a suitable separate expression for this flux is then an important part of the complete specification of the problem. We show that, contrary to previous suggestions, the amount of energy carried across the interface by neutrinos may well be at least comparable to that carried by the hydrodynamical flow during a significant part of the transition, and we present a revised discussion of the baryon concentration mechanism which may be associated with this.