Could the cosmic acceleration be transient? A cosmographic evaluation

TL;DR

This study uses cosmography to analyze supernova data, suggesting the universe's accelerated expansion might be slowing down and could be a transient phase, challenging the standard cosmological model.

Contribution

It demonstrates that a fourth-order cosmographic expansion allows for the possibility of transient cosmic acceleration, independent of specific gravity or matter assumptions.

Findings

Likelihood of current deceleration parameter q0 > 0

Cosmic acceleration may have peaked and is now decreasing

Transient acceleration compatible with supernova data

Abstract

A possible slowing down of the cosmic expansion is investigated through a cosmographic approach. By expanding the luminosity distance to fourth order and fitting the SN Ia data from the most recent compilations (Union, Constitution and Union 2), the marginal likelihood distributions for the deceleration parameter today suggest a recent reduction of the cosmic acceleration and indicate that there is a considerable probability for $q_0>0$. Also in contrast to the prediction of the $\Lambda$CDM model, the cosmographic $q(z)$ reconstruction permits a cosmic expansion history where the cosmic acceleration could already have peaked and be presently slowing down, which would imply that the recent accelerated expansion of the Universe is a transient phenomenon. It is also shown that to describe a transient acceleration the luminosity distance needs to be expanded at least to fourth order. The present cosmographic results depend neither on the validity of general relativity nor on the matter-energy contents of the Universe.