  We consider the problem of picking a physically motivated vacuum state on a
spherically symmetric spacetime with an extra conformal Killing vector, as
opposed to an extra Killing vector as in the Schwarzschild case. Considering a
conformal symmetry instead of a symmetry allows us to consider spacetimes that
are dynamical and not static (like Schwarzschild). The extra conformal symmetry
allows us to calculate the response of particle detectors however. We look at
the specific example of a self-similar LTB spacetime that represents a
spherically symmetric but inhomogeneous cosmology. We remark that the above
procedure might be applied to a spherically symmetric collapse solution that
represents black hole formation so that one can calculate the detailed spectrum
of Hawking radiation during a collapse.
