Junction conditions of Friedmann-Robertson-Walker space-times

We complete a classification of junctions of two Friedmann-Robertson-Walker space-times bounded by a spherical thin wall. Our analysis covers superhorizon bubbles and thus complements the previous work of Berezin, Kuzumin, and Tkachev. Contrary to subhorizon bubbles, various topology types for superhorizon bubbles are possible, regardless of the sign of the extrinsic curvature. We also derive a formula for the peculiar velocity of a domain wall for all types of junction.