Ozgur Akarsu, Tekin Dereli, Suresh Kumar, Lixin Xu
We study linearly varying deceleration parameter in terms of cosmic time t (LVDPt) with the companion linearly varying deceleration parameter in terms of cosmic redshift z (LVDPz) and in terms of cosmic scale factor a (LVDPa). We investigate in detail the kinematics and the fate of the Universe by confronting the three LVDP laws with the latest observational data from H(z) compilation (25 data points) and SN Ia Union2.1 compilation (580 data points). The study reveals that the LVDPt law is superior than LVDPz and LVDPa laws in many aspects. In particular, the goodness of fit to the observational data is found to be the best for the LVDPt law. The kinematics and dynamics (assuming general relativity) of the Universe is further studied by considering the LVDPt law in comparison with the standard LCDM model. It is found that these two models are observationally indistinguishable but the LVDPt fits the data slightly better than the LCDM model. These two models exhibit a very similar behavior for a long passage of time but make slightly different predictions for the earlier times of the Universe with considerably different predictions on the future of the Universe. According to the LVDPt model, the accelerating expansion of the Universe started when the Universe was 7.148+/-0.923 Gyr old at redshift 0.703+0.356/-0.148 and the age of the present Universe is 13.460+/-0.899 Gyr, whereas these values are found to be 7.233+/-0.225 Gyr, 0.682+/-0.082 and 13.389+/-0.289 Gyr in the LCDM model. Observational constraints on cosmic doomsday are carried out in the context of the LVDPt model, and it is found that the Universe will end in Big Rip when the age of the Universe is 36.602+/-7.930 Gyr.
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http://arxiv.org/abs/1305.5190
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