The damping of the effective value of the cosmological constant by an unstable scalar field is investigated. It is shown that an instability induced by coupling to spacetime curvature can cause cosmological-constant-damping behavior which reduces the present-day value of the cosmological constant to a value which is consistent with observation. It is also shown that localized distributions of matter such as stars need not be unstable in the presence of such unstable fields.

• Received 9 January 1987

DOI:https://doi.org/10.1103/PhysRevD.35.2339