  On this work, we consider a particle moving in front of a dielectric plate,
and study two of the most relevant effects of the vacuum field fluctuations:
the dissipation, and the decoherence of the particle's internal degrees of
freedom. We consider the particle to follow a classical, macroscopically-fixed
trajectory. To study the dissipative effects, we calculate the in-out effective
action by functionally integrating over the vacuum field and the microscopic
degrees of freedom of both the plate and the particle. This in-out effective
action develops an imaginary part, hence a non-vanishing probability for the
decay (because of friction) of the initial vacuum state. We analyze how the
dissipation is affected by the relative velocity between the particle and the
plate and the properties of the microscopic degrees of freedom. In order to
study the effects of decoherence over the internal degrees of freedom of the
particle, we calculate the CTP or Schwinger-Keldysh influence action, by
functionally integrating over the vacuum field and the microscopic degrees of
freedom of the plate. We estimate the decoherence time as the time needed by
two different quantum configurations (of the internal degree of freedom of the
particle) to be possible to differentiate from one another. We analyze the way
in which the presence of the mirror affects the decoherence, and the possible
ways to maximize or reduce its effects.
