  Sen has recently drawn attention to an exact time-dependent Boundary
Conformal Field Theory with the space-time interpretation of brane creation and
annihilation. An interesting limit of this BCFT is formally equivalent to an
array of D-branes located in imaginary time. This raises the question: what is
the meaning of D-branes in imaginary time? The answer we propose is that
D-branes in imaginary time define purely closed string backgrounds. In
particular we prove that the disk scattering amplitude of m closed strings off
an arbitrary configuration of imaginary branes is equivalent to a sphere
amplitude with m+1 closed string insertions. The extra puncture is a specific
closed string state, generically normalizable, that depends on the details of
the brane configuration. We study in some detail the special case of the array
of imaginary D-branes related to Sen's BCFT and comment on its space-time
interpretation. We point out that a certain limit of our set-up allows to study
classical black hole creation and suggests a relation between Choptuik's
critical behavior and a phase-transition a` la Gregory-Laflamme. We speculate
that open string field theory on imaginary D-branes is dual to string theory on
the corresponding closed string background.
