  We propose that perturbative quantum field theory and string theory can be
consistently modified in the infrared to eliminate, in a radiatively stable
manner, tadpole instabilities that arise after supersymmetry breaking. This is
achieved by deforming the propagators of classically massless scalar fields and
the graviton so as to cancel the contribution of their zero modes. In string
theory, this modification of propagators is accomplished by perturbatively
deforming the world-sheet action with bi-local operators similar to those that
arise in double-trace deformations of AdS/CFT. This results in a perturbatively
finite and unitary S-matrix (in the case of string theory, this claim depends
on standard assumptions about unitarity in covariant string diagrammatics). The
S-matrix is parameterized by arbitrary scalar VEVs, which exacerbates the
vacuum degeneracy problem. However, for generic values of these parameters,
quantum effects produce masses for the nonzero modes of the scalars, lifting
the fluctuating components of the moduli. Warning: in the case of string
theory, the simple prescription discussed in this paper fails to decouple BRST
trivial modes from the physical S-matrix. A procedure aimed at correcting this
is under investigation.
