Bubble wall dynamics from nonequilibrium quantum field theory

Abstract: We derive the coupled dynamics between the bubble wall and the plasma from first principles using nonequilibrium quantum field theory. The commonly used equation of motion of the bubble wall in the kinetic approach is shown to be incomplete. In the language of the two-particle-irreducible effective action, the conventional equation misses higher-loop terms generated by the condensate-particle type vertices (e.g.,~$\varphi\phi\chi^2$, where $\varphi$ is the background field describing the bubble wall, $\phi$ the corresponding particle excitation and $\chi$ another particle species in the plasma). From the missing terms, we identify an additional dissipative friction which is contributed by particle production processes from the condensate-particle type vertices. We also show how other transmission processes beyond the 1-to-1 elementary transmission studied in the literature for ultrarelativistic bubble walls, e.g., 1-to-1 mixing and 1-to-2 transition radiation, can be understood from the kinetic approach.