Spintessence: a possible candidate as a driver of the late time cosmic acceleration

In this paper, it is shown completely analytically that a spintessence model in the dust dominated universe can very well serve the purpose of providing an early deceleration and a present day acceleration. The stunning results of the observations on the luminosity redshift relation of some distant supernovae [1, 2], that the universe is currently undergoing an accelerated phase of expansion, poses a serious challenge for the standard big bang cosmology. As the standard gravitating matter gives rise to an attractive field only, this challenge is negotiated in the standard model by invoking some field which gives rise to an effective negative pressure. For many a reason, a dynamical ‘dark energy’ is favoured against the apparently obvious choice of a cosmological constant Λ for providing this negative pressure [3]. This dynamical dark energy is called a quintessence matter. It cannot be overlooked that a successful explanation of the formation of structures in the early matter dominated era crucially requires an effectively attractive gravitational field and thus a decelerated phase of expansion must have been witnessed by an early epoch of matter dominated universe itself. Very recently Padmanabhan and Roy Chowdhury [4] showed that the data set, only showing the accelerated phase of expansion, can well be interpreted in terms of a decelerated expansion in disguise. The acceleration only becomes meaningful if the full data set shows deceleration upto a certain age of the universe and an acceleration after that (see also ref [5]). In keeping with such theoretical requirements, actual observations indeed indicate such a shift in the mode of expansion deceleration upto a higher redshift regime (about z ∼ 1.5) and acceleration in more recent era, i.e, for lesser values of z [6]. ∗email: [email protected]