  As an attempt to solve the black hole information loss paradox, recently
there has been the suggestion that, due to semi-classical effects, a
pre-Hawking radiation must exist during the gravitational collapse of matter,
which in turn prevents the apparent horizon from forming. Assuming the
pre-Hawking radiation does exist, here we argue the opposite. First we note
that the stress energy tensor near the horizon for the pre-Hawking radiation is
far too small to do anything to the motion of a collapsing shell. Thus the
shell will always cross the apparent horizon within a finite proper time.
Moreovall, the amount of energy that can be radiated must be less than half of
the total initial energy (if the particle starts at rest at infinity) before
the shell becomes a null shell and cannot radiate any more without becoming
tachyonic. We conclude that for any gravitational collapsing process within
Einstein gravity and semi-classical quantum field theory, the formation of the
apparent horizon is inevitable. Pre-Hawking radiation is therefore not a valid
solution to the information paradox.
