Future evolution of cosmic structure in an accelerating universe

Current cosmological data indicate that our universe contains a substantial component of dark vacuum energy that is driving the cosmos to accelerate. We examine the immediate and longer term consequences of this dark energy ( assumed here to have a constant density). Using analytic calculations and supporting numerical simulations, we present criteria for test bodies to remain bound to existing structures. We show that collapsed halos become spatially isolated and dynamically relax to a particular density pro. le with logarithmic slope steeper than - 3 at radii beyond r(200). The asymptotic form of the spacetime metric is then specified. We develop this scenario further by determining the effects of the accelerating expansion on the background radiation fields and individual particles. In an appendix, we generalize these results to include quintessence.