  We show that while some non-uniformly accelerating observers (NUAOs) do
indeed see a Bose-Einstein distribution of particles for the expectation value
of the number operator in the Minkowski vacuum state, the density matrix is
non-thermal and therefore a definition of temperature is not warranted. This is
due to the fact that our NUAOs do not see event horizons in the spacetime. More
specifically, the Minkowski vacuum state is perceived by our NUAOs as a
single-mode squeezed state as opposed to the two-mode squeezed state
characteristic of uniformly accelerating observers. Both single and two-mode
squeezed states are pure quantum states; however, tracing over degrees of
freedom in one of the modes of the two-mode squeezed state reduces the pure
density matrix to a thermal density matrix. It is this property in the two-mode
squeezed state that allows one to consistently define a temperature. In the
single-mode case, an equivalent tracing is neither required nor available.
