Constraints on Decelerating Cosmologies

In a steadily decelerating Universe which is matter dominated but open with a density ratio to the critical density 0.26, H₀t₀ < 1 (Peacock 1999). A Universe which is accelerating now, and has 0.26 and a vacuum energy density ratio 0.74, has H₀t₀ 1 (Carroll, Press & Turner 1992). The uncertainty in the product of equations 1 & 2 can be calculated from the normally distributed errors in H₀ and t₀. Figure 1 shows the probability distribution for H₀t₀ for two assumptions: t_f = 0 and 1 Gyr.

Figure 1: Probability distribution of the product of H₀ and t₀ with their associated uncertainties. Above: with t_f = 0. Below: with t_f = 1 Gyr.

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