Particle Production in Accelerated Thin Bubbles

We investigate the creation of scalar particles inside a region delimited by a bubble which is expanding with non-zero acceleration. The bubble is modelled as a thin shell and plays the role of a moving boundary, thus influencing the fluctuations of the test scalar field inside it. Bubbles expanding in Minkowski spacetime as well as those dividing two de Sitter spacetimes are explored in a unified way. Our results for the Bogoliubov coefficient $\beta_k$ in the adiabatic approximation show that in all cases the creation of scalar particles decreases with the mass, and is much more significant in the case of nonzero curvature. They also show that the dynamics of the bubble and its size are relevant for particle creation, but in the dS-dS case the combination of both effects leads to a behaviour different from that of Minkowski space-time, due to the presence of a length scale (the Hubble radius of the internal geometry).
Comment: 14 pages, 3 figures