  The "trousers" spacetime is a pair of flat 2D cylinders ("legs") merging into
into a single one ("trunk"). In spite of its simplicity this spacetime has a
few features (including, in particular, a naked singularity in the "crotch")
each of which is presumably unphysical, but for none of which a mechanism is
known able to prevent its occurrence. Therefore it is interesting and important
to study the behavior of the quantum fields in such a space. Anderson and
DeWitt were the first to consider the free scalar field in the trousers
spacetime. They argued that the crotch singularity produces an infinitely
bright flash, which was interpreted as evidence that the topology of space is
dynamically preserved. Similar divergencies were later discovered by Manogue,
Copeland and Dray who used a more exotic quantization scheme. Later yet the
same result obtained within a somewhat different approach led Sorkin to the
conclusion that the topological transition in question is suppressed in quantum
gravity.
  In this paper I show that the Anderson--DeWitt divergence is an artifact of
their choice of the Fock space. By choosing a different one-particle Hilbert
space one gets a quantum state in which the components of the stress-energy
tensor (SET) are bounded in the frame of a free-falling observer.
