  In this paper we investigate the relation between the bulk and boundary in
AdS/CFT. We first discuss the relation between the Poincare and the global
vacua, and then study various probes of the bulk from the boundary theory point
of view. We derive expressions for retarded propagators and note that objects
in free fall look like expanding bubbles in the boundary theory. We also study
several Yang-Mills theory examples where we investigate thermal screening and
confinement using propagators. In the case of confinement we also calculate the
profile of a flux tube and provide an alternative derivation of the tension.

High Energy Physics - Theory