  We study phase transitions induced by topological defects in Abelian gauge
theories of open p-branes in (d+1) space-time dimensions. Starting from a
massive antisymmetric tensor theory for open p-branes we show how the
condensation of topological defects can lead to a decoupled phase with a
massless tensor coupled to closed (p-1)-branes and a massive tensor coupled to
open (p+1)-branes. We also consider the case, relevant in string theory, in
which the boundaries of the p-branes are constrained to live on a Dirichlet
n-branes.
