Evolution of Vacuum Bubbles Embeded in Inhomogeneous Spacetimes
  We study the propagation of bubbles of new vacuum in a radially inhomogeneous background filled with dust or radiation, and including a cosmological constant, as a first step in the analysis of the influence of inhomogeneities in the evolution of an inflating region. We also compare the cases with dust and radiation backgrounds and show that the evolution of the bubble in radiation environments is notably different from that in the corresponding dust cases, both for homogeneous and inhomogeneous ambients, leading to appreciable differences in the evolution of the proper radius of the bubble. 
F. A. Teppa Pannia, S. E. Perez Bergliaffa
gr-qc astro-ph.CO