  We study the change in topological entanglement entropy that occurs when a
two-dimensional system in a topologically ordered phase undergoes a transition
to another such phase due to the formation of a Bose condensate. We also
consider the topological entanglement entropy of systems with domains in
different topological phases, and of phase boundaries between these domains. We
calculate the topological entropy of these interfaces and derive two
fundamental relations between the interface topological entropy and the bulk
topological entropies on both sides of the interface.
