  In this paper we study the effects of quantum scalar field vacuum
fluctuations on scalar test particles in an analog model for the
Friedmann-Robertson-Walker spatially flat geometry. In this scenario, the cases
with one and two perfectly reflecting plane boundaries are considered as well
the case without boundary. We find that the particles can undergo Brownian
motion with a nonzero mean squared velocity induced by the quantum vacuum
fluctuations due to the time dependent background and the presence of the
boundaries. Typical singularities which appears due to the presence of the
boundaries in flat spacetime can be naturally regularized for an asymptotically
bounded expanding scale function. Thus, shifts in the velocity could be, at
least in principle, detectable experimentally. The possibility to implement
this observation in an analog cosmological model by the use of a Bose-Einstein
condensate is also discussed.
