Session 26. Deep Surveys
Display, Wednesday, November 8, 2000, 8:00am-6:00pm, Bora Bora Ballroom

## [26.22] Smooth Energy: Cosmological Constant or Quintessence?

S. Bludman (DESY, Hamburg & University of Pennsylvania), M. Roos (University of Helsinki, Finland)

For a flat universe presently dominated by smooth energy, either cosmological constant (LCDM) or quintessence (QCDM), we calculate the asymptotic collapsed mass fraction as function of the present ratio of smooth energy to matter energy \mathcal{R}. Identifying the normalized collapsed fraction as a conditional probability for habitable galaxies, we observe that the observed present ratio \mathcal{R} ~ 2 is likely in LCDM, but more likely in QCDM. Inverse application of Bayes' Theorem makes the Anthropic Principle a predictive scientific principle: the data implies that the prior probability for \mathcal{R} must be essentially flat over the anthropically allowed range. Interpreting this prior as a distribution over {\em theories} lets us predict that any future theory of initial conditions must be indifferent to \mathcal{R}. This application of the Anthropic Principle does not demand the existence of other universes.