Kinematic Constraints to the Transition Redshift from SNe Ia Union Data

Abstract

The kinematic approach to cosmological tests provides a direct evidence to the present accelerating stage of the universe which does not depend on the validity of general relativity, as well as on the matter-energy content of the Universe. In this context, we consider here a linear two-parameter expansion for the decelerating parameter, $q(z)=q_0+q_{1}z$, where $q_0$ and $q_1$ are arbitrary constants to be constrained by the Union supernovae data. By assuming a flat Universe we find that the best fit to the pair of free parameters is ($q_0,q_1$) = ($-0.73,1.5)$ whereas the transition redshift is $z_t=0.49_{-0.07}^{+0.14}$ ($1\sigma$) ${}_{-0.12}^{+0.54}$ ($2\sigma$). This kinematic result is in agreement with some independent analyzes and accommodates more easily many dynamical flat models (like $\Lambda$CDM).

10 pages, 4 figures, 1 table

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