  We define an effective potential describing all massless and massive modes in
the supergravity limit of string/M theory compactification which is valid
off-shell, i.e. without imposing the equations of motion. If we neglect the
warp factor, it is unbounded below, as is the case for the action in Euclidean
quantum gravity. By study of the constraint which determines the warp factor,
we solve this problem, obtaining a physically satisfying and tractable
description of the dynamics of the warp factor.
