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arXiv 1003.2881hep-thastro-ph.COgr-qc
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Dirac-Born-Infeld场的宇宙动力学

Cosmological Dynamics of a Dirac-Born-Infeld field

Edmund J. Copeland, Shuntaro Mizuno, Maryam Shaeri

备注：
24 pages, 7 figures, minor corrections, references added
发表信息：
Phys.Rev.D81:123501,2010
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摘要：

我们分析了一个狄拉克玻恩因菲尔德（DBI）场在宇宙学设置，其中包括一个完美的流体的动力学。通过引入方便的动力学变量，我们证明了当DBI场的势和膜张力是DBI场的任意幂律或指数函数时，演化方程形成一个自治系统.特别是，我们发现缩放的解决方案可以存在的权力时，在潜在的和扭曲因子满足特定的关系。一类新的固定点的解决方案，得到相应的点，最初出现在发展方程中的奇异，但仔细检查，实际上是很好的定义。在所有情况下，我们进行相空间分析，并获得系统的后期吸引子结构。特别值得注意的是，当考虑DBI暴胀中的宇宙学扰动时，是一个固定点解，其中洛伦兹因子是一个有限的大常数，DBI场的状态参数方程是$w=-1$。由于在这种情况下，声速$c_s$变为恒定，因此可以认为该解充当扰动的良好背景。

英文摘要：

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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