  Diracs hole theory (HT) and quantum field theory (QFT) are generally
considered to be equivalent to each other. However, it has been recently shown
by several researchers that this is not necessarily the case. When the change
in the vacuum energy was calculated for a time independent perturbation HT and
QFT yielded different results. In this paper we extend this discussion to
include a time dependent perturbation for which the exact solution to the Dirac
equation is known. It will be shown that for this case, also, HT and QFT yield
different results. In addition, there will be some discussion of the problem of
anomalies in QFT.
