Can the Universe decelerate in the future

Abstract

The possibility of an expanding decelerating Universe in the distant future is investigated in the context of a quintessence scalar field cosmology. Such a conceivable evolution is tested against SNe Ia and H(z) cosmic chronometers data, and also through a model independent method based on Gaussian processes. The scalar field model is an extension of the exponential Ratra-Peebles (RP) quintessential cosmology whose potential now depends on a pair of parameters (α,λ) and predicts a decelerated expansion in the future. Different from the RP approach the α parameter allows for a decelerating cosmology in the future thereby frustrating the inevitable evolution for a de Sitter cosmology as predicted by the cosmic concordance model (ΛCDM). The statistical model analysis is updated with the most recent SNe Ia and H(z) data thereby obtaining H0=68.6±3.7 km/s/Mpc, ωφ0=0.735-0.069+0.083, α<6.56 and λ<0.879 (at 2σ c.l.). It is also found that the extended RP model allows for a future deceleration both for H(z) and SNe Ia data. In the (model-independent) Gaussian processes analysis, however, future deceleration is allowed only in the case of H(z) data.