  We modify and extend an earlier proposal by Brown and Teitelboim to relax the
effective cosmological term by nucleation of branes coupled to a three-index
gauge potential. Microscopic considerations from string/M theory suggest two
major innovations in the framework. First, the dependence of brane properties
on the compactification of extra dimensions may generate a very small quantized
unit for jumps in the effective cosmological term. Second, internal degrees of
freedom for multiply coincident branes may enhance tunneling rates by
exponentially large density of states factors. These new features essentially
alter the relaxation dynamics. By requiring stability on the scale of the
lifetime of the universe, rather than absolute stability, we derive a
non-trivial relation between the supersymmetry breaking scale and the value of
the cosmological term. It is plausibly, though not certainly, satisfied in
Nature.
