Approximate black holes from a variable cosmological constant
  The small or zero cosmological constant, $\Lambda$, probably results from a macroscopic cancellation mechanism of the zero-point energies. However, nearby horizon surfaces any macroscopic mechanism is expected to result in imperfect cancellations. A phenomenological description is given for the residual variable cosmological constant. In the static, spherically symmetric case it produces approximate black holes. The model describes the case of exponential decay by $\Box\ln\Lambda=-3a$, were $a$ is a positive constant. 
Maurice H.P.M. van Putten (MIT)