the dark energy properties of the dirac–born–infeld action暗能量的属性dirac-born-infeld行动.pdf

Entropy 2012, 14, 1203-1220; doi:10.3390/ OPEN ACCESS entropy ISSN 1099-4300 /journal/entropy Article The Dark Energy Properties of the Dirac–Born–Infeld Action Xinyou Zhang *, Qing Zhang and Yongchang Huang Institute of Theoretical Physics, Beijing University of Technology, Beijing 100124, China; E-Mail: bjutychuang@ Department of Physics, Imperial College London, South Kensington campus, London, SW7 2AZ, UK; E-Mail: zxyypzqzxh@ Kavli Institute for Theoretical Physics, Chinese Academy of Sciences, Beijing 100080, China CCAST (World Lab.), P.O.Box 8730, Beijing 100080, China * Author to whom correspondence should be addressed; E-Mail:xinyouzhang@. Received: 1 May 2012; in revised form: 30 May 2012 / Accepted: 18 June 2012 / Published: 9 July 2012 Abstract: Introducing a new potential, we deduce a general Lagrangian for Dirac–Born– Infeld (DBI) inflation, in which the determinant of the induced metric naturally includes the kinetic energy and the potential energy. In particular, the potential energy and kinetic energy can convert into each other at any same order, which is in agreement with the limit of classical physics. We also present a general sound speed in the evolutions of the universe, and the exact expressions of energy-momentum tensor, pressure and density. Furthermore, from the results we obtain the new equation of states. The analytic form of the action that is consistent with data turns out to be surprisingly simple and easy to categorize. Finally, we examine properties of the dark energy and introduce a novel mecha