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arXiv 0903.2065hep-thastro-ph.COgr-qchep-ph
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暴胀宇宙学中的trans-Planckian问题

The Trans-Planckian Problem for Inflationary Cosmology Revisited

Robert Brandenberger, Xinmin Zhang

摘要:

我们考虑一个暴胀宇宙模型,在这个模型中,加速膨胀阶段之前是一个非奇异的反弹和一个包含减速阶段的收缩阶段。我们遵循的波动,退出哈勃半径在辐射为主的收缩阶段的量子真空波动,重新进入哈勃半径在通货紧缩期间和重新交叉在阶段的通货膨胀。演化的波动使用广义相对论线性微扰方程,我们发现,他们退出哈勃半径在通货膨胀期间不具有标度不变的光谱,但具有高度红色的光谱与指数$n_s = -3$。我们还表明,波动的反作用限制了通货紧缩的时间间隔。我们的玩具模型表明,无论是跨普朗克问题的宇宙学扰动和反反应效应的暴胀宇宙学的重要性。首先,在不理解普朗克尺度物理和暴胀之前的阶段的情况下,当微扰在晚些时候离开哈勃半径时,将微扰置于其局部真空状态是一个不平凡的假设。第二,波动的反作用效应会对背景产生重要影响。

英文摘要:

We consider an inflationary universe model in which the phase of accelerated expansion was preceded by a non-singular bounce and a period of contraction which involves a phase of deceleration. We follow fluctuations which exit the Hubble radius in the radiation-dominated contracting phase as quantum vacuum fluctuations, re-enter the Hubble radius in the deflationary period and re-cross during the phase of inflationary expansion. Evolving the fluctuations using the general relativistic linear perturbation equations, we find that they exit the Hubble radius during inflation not with a scale-invariant spectrum, but with a highly red spectrum with index $n_s = -3$. We also show that the back-reaction of fluctuations limits the time interval of deflation. Our toy model demonstrates the importance for inflationary cosmology both of the trans-Planckian problem for cosmological perturbations and of back-reaction effects . Firstly, without understanding both Planck-scale physics and the phase which preceded inflation, it is a non-trivial assumption to take the perturbations to be in their local vacuum state when they exit the Hubble radius at late times. Secondly, the back-reaction effects of fluctuations can influence the background in an important way.

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