  Within the frame of macroscopic quantum electrodynamics in causal media, the
van der Waals interaction between an atomic system and an arbitrary arrangement
of dispersing and absorbing dielectric bodies including metals is studied. It
is shown that the minimal-coupling scheme and the multipolar-coupling scheme
lead to essentially the same formula for the van der Waals potential. As an
application, the vdW potential of an atom in the presence of a sphere is
derived. Closed expressions for the long-distance (retardation) and
short-distance (non-retardation) limits are given, and the effect of material
absorption is discussed.
