  We provide a description of spontaneous emission in a dispersive and
dissipative linear inhomogeneous medium based on the generalized
Huttner-Barnett model [Phys. Rev. A 46, 4306 (1992)]. Our discussion considers
on an equal footing both the photonic and material fluctuations which are
necessary to preserve unitarity of the quantum evolution. Within this approach
we justify the results obtained in the past using the Langevin noise method
that neglects the removal of photonic fluctuations. We finally discuss the
concept of local density of states (LDOS) in a lossy and dispersive
inhomogeneous environment that provides a basis for theoretical studies of
fluorescent emitters near plasmonic and polaritonic antennas.
