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arXiv 0907.1772astro-ph.CO
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无标量场的原初涨落

Primordial fluctuations without scalar fields

J. Magueijo, J. Noller

摘要:

我们重新审视流体动力学的波动问题,热力学物质是否可以解释我们宇宙中观察到的结构。我们考虑物质的可变状态方程$w=p_0/\ep_0$和随之而来的(绝热假设下)密度相关的声速,$c_s$。我们发现,当模式在哈勃半径内开始时,设置的可能性范围有限,然后离开它并冻结。对于膨胀的宇宙,幂律$w(\ep_0)$模型被排除在外(除了$c_s^2\propto w \ll 1$,需要后拉伸种子波动);但$c_s$中更尖锐的轮廓确实解决了视界问题。其中,在$c_s$的相变是值得注意的尺度不变的波动,如果初始条件是热的。对于收缩宇宙,所有幂律$w(\ep_0)$都能解决视界问题,但只有一个能导致标度不变性:$w\propto \ep_0^2$和$c_s\propto \ep_0$。该模型绕过了单标量场循环模型的许多问题(对于单标量场循环模型,$w$较大但恒定)。

英文摘要:

We revisit the question of whether fluctuations in hydrodynamical, adiabatical matter could explain the observed structures in our Universe. We consider matter with variable equation of state $w=p_0/\ep_0$ and a concomitant (under the adiabatic assumption) density dependent speed of sound, $c_s$. We find a limited range of possibilities for a set up when modes start inside the Hubble radius, then leaving it and freezing out. For expanding Universes, power-law $w(\ep_0)$ models are ruled out (except when $c_s^2\propto w \ll 1$, requiring post-stretching the seeded fluctuations); but sharper profiles in $c_s$ do solve the horizon problem. Among these, a phase transition in $c_s$ is notable for leading to scale-invariant fluctuations if the initial conditions are thermal. For contracting Universes all power-law $w(\ep_0)$ solve the horizon problem, but only one leads to scale-invariance: $w\propto \ep_0^2$ and $c_s\propto \ep_0$. This model bypasses a number of problems with single scalar field cyclic models (for which $w$ is large but constant).

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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