We provide a method to decompose the two-point function of a quantum field on
a warped manifold in terms of fields living on a lower-dimensional manifold. We
discuss explicit applications to Minkowski, de Sitter and anti-de Sitter
quantum field theories. This decomposition presents a remarkable analogy with
the holography principle, in the sense that physics in d+1 dimensions may be
encoded into the physics in one dimension less. Moreover in a context a la
Randall--Sundrum, the method outlined here allows a mechanism of generation of
mass-spectra in the 3-brane (or more generally a d-1-brane).Comment: 25 page
