  The present thesis deals with some properties of classical and quantum scalar
fields in an inhomogeneous and/or time-dependent background, focusing on models
where the latter can be described as a curved space-time with an event horizon.
While naturally formulated in a gravitational context, such models extend to
many physical systems with an effective Lorentz invariance at low energy. We
shall see how this effective symmetry allows one to relate the behavior of
perturbations in these systems to black-hole physics, what are its limitations,
and in which sense results thus obtained are "analogous" to their general
relativistic counterparts. The first chapter serves as a general introduction.
A few notions from Einstein's theory of gravity are introduced and a derivation
of Hawking radiation is sketched. The correspondence with low-energy systems is
then explained through three important examples. The next four chapters each
details one of the works completed during this thesis, updated and slightly
reorganized to account for new developments which occurred after their
publication. The other articles I contributed to are summarized in the last
chapter, before the general conclusion.
