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ISRN Astronomy and Astrophysics
Volume 2011 (2011), Article ID 523617, 5 pages
http://dx.doi.org/10.5402/2011/523617
Research Article

An Old Universe in K-Essence Cosmology

1College of Physical Science and Technology, Hebei University, Baoding 071002, China
2Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, P.O. Box 918-3, Beijing 100039, China

Received 21 November 2011; Accepted 27 December 2011

Academic Editor: P. Marziani

Copyright © 2011 Rong-Jia Yang et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Models in which the Lagrangian contains only a kinetic factor and does not depend explicitly on the field itself in k-essence cosmology are considered. In the case of a constant potential, we obtain an exact analytic solution of k-essence, 𝑤 𝑘 = ( 3 𝛼 2 ) / 3 𝛼 , under a simple hypothesis, 𝑎 = 𝑎 0 ( 𝑡 / 𝑡 0 ) 𝛼 , but without any assumption about the form of 𝐹 ( 𝑋 ) . In purely kinetic k-essence model, the acceleration can only be induced after the matter-dominated epoch; the Universe is about 3 3 . 5 + 4 . 2 3 . 4 Gyr old now and about 3.1 Gyr old at 𝑧 = 3 . 9 which is consistent with the fact of quasar observation, while this observation contradicts with the prediction of ΛCDM model, and the year where a transition from deceleration to acceleration expansion is about from 18.43 Gyr to 25.2 Gyr after the beginning of the Universe. These results may offer clues to test observationally the k-essence scenario in the future.