  We study the quantum dissipative dynamics of a particle coupled linearly to a
set of two-level systems (the heat bath) via the master equation method which
we extract from the path integral formalism independently from the form of the
bath spectral density. We compare our results with the standard models based on
bosonic heat baths showing their main differences and similarities. In
particular, we study special forms for the spectral density of the bath which
give results quite different from the standard models.
