Observation of cosmic acceleration and determining the fate of the universe

Current observations of type-Ia supernovae provide evidence for cosmic acce leration out to a redshift of z less than or similar to 1, leading to the p ossibility that the universe is entering an inflationary epoch. However, in flation can take place only if vacuum energy (or other sufficiently slowly redshifting source of energy density) dominates the energy density of a reg ion of physical radius 1/H. We argue that, for the best-fit values of Omega (Lambda) = 0.8 and Omega(m) = 0.2 inferred from the supernovae data, one mu st confirm cosmic acceleration out to at least z similar or equal to 1.8 to infer that our portion of the universe is inflating. If Omega(Lambda) < 0. 736 then no present-day measurement can confirm or falsify that inference.