  In quantum field theory, the vacuum is widely considered to be a complex
medium populated with virtual particle + antiparticle pairs. To an observer
experiencing uniform acceleration, it is generally held that these virtual
particles become real, appearing as a gas at a temperature which grows with the
acceleration. This is the Unruh effect. However, it can be shown that vacuum
complexity is an artifact, produced by treating quantum field theory in a
manner that does not manifestly enforce causality. Choosing a quantization
approach that patently enforces causality, the quantum field theory vacuum is
barren, bereft even of virtual particles. We show that acceleration has no
effect on a trivial vacuum; hence, there is no Unruh effect in such a treatment
of quantum field theory. Since the standard calculations suggesting an Unruh
effect are formally consistent, insofar as they have been completed, there must
be a cancelling contribution that is omitted in the usual analyses. We argue
that it is the dynamical action of conventional Lorentz transformations on the
structure of an Unruh detector. Given the equivalence principle, an Unruh
effect would correspond to black hole radiation. Thus, our perspective has
significant consequences for quantum gravity and black hole physics: no Unruh
effect entails the absence of black hole radiation evaporation.
