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arXiv · 1003.2881

Cosmological Dynamics of a Dirac-Born-Infeld field

Edmund J. Copeland·Shuntaro Mizuno·Maryam Shaeri
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Abstract

We analyze the dynamics of a Dirac-Born-Infeld (DBI) field in a cosmological set-up which includes a perfect fluid. Introducing convenient dynamical variables, we show the evolution equations form an autonomous system when the potential and the brane tension of the DBI field are arbitrary power-law or exponential functions of the DBI field. In particular we find scaling solutions can exist when powers of the field in the potential and warp-factor satisfy specific relations. A new class of fixed-point solutions are obtained corresponding to points which initially appear singular in the evolution equations, but on closer inspection are actually well defined. In all cases, we perform a phase-space analysis and obtain the late-time attractor structure of the system. Of particular note when considering cosmological perturbations in DBI inflation is a fixed-point solution where the Lorentz factor is a finite large constant and the equation of state parameter of the DBI field is $w=-1$. Since in this case the speed of sound $c_s$ becomes constant, the solution can be thought to serve as a good background to perturb about.

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Edmund J. Copeland, Shuntaro Mizuno, Maryam Shaeri. 2010-03-30. Cosmological Dynamics of a Dirac-Born-Infeld field. https://doi.org/10.1103/physrevd.81.123501

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