EverpresentΛ. II. Structural stability

Ideas from causal set theory lead to a fluctuating, time-dependent cosmological constant of the right order of magnitude to match currently quoted ``dark energy'' values. Although this effect was predicted some time ago [R. D. Sorkin, in Relativity and Gravitation: Classical and Quantum, Proceedings of the SILARG VII Conference, Cocoyoc, Mexico, 1990, edited by J. C. D'Olivo, E. Nahmad-Achar, M. Rosenbaum, M. P. Ryan, L. F. Urrutia, and F. Zertuche (World Scientific, Singapore, 1991), pp. 150\char21{}173; Rafael D. Sorkin, Int. J. Theor. Phys. 36, 2759 (1997).], it is only more recently that a more detailed phenomenological model of a fluctuating $$\Lambda${}$ was introduced and simulated numerically [M. Ahmed, S. Dodelson, P. Greene, and R. D. Sorkin, Phys. Rev. D 69, 103523 (2004).]. In this paper we continue the investigation by studying the sensitivity of the model to some of the ad hoc choices made in setting it up.