Entropy of gravitons produced in the early universe
Entropy of gravitons produced in the early universe
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早期宇宙中产生的引力子的熵
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
A. Starobinsky
中科院分区：
文献类型：
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作者：
Claus Kiefer;D. Polarski;A. Starobinsky
在早期宇宙暴胀阶段，量子真空涨落产生的引力子的熵为零，因为它们反映了纯态的时间演化（挤压），尽管它们的占据数很大。引力子的非零熵[退相干后的经典引力波（GW）]可以通过粗粒化获得。后者必须在物理上合理，并且不应与观察限制相矛盾。我们提出了两种粗粒化方法，其中引力波背景的每个傅立叶模式的固定时间相位仍然可观察到：一种基于量子纠缠，另一种基于次级引力波背景的存在。这些提议被证明是相互一致的。他们得出的结果是，原始引力波背景的熵比之前认为的要小得多。这种差异可以归因于有关宇宙规则（暴胀）初始状态的信息，该信息存储在该背景中，并且特别是在 CMB 温度各向异性和偏振的多极谱中出现原始峰（标量扰动情况下的声学峰）时显现出来。
Gravitons produced from quantum vacuum fluctuations during an inflationary stage in the early Universe have zero entropy as far as they reflect the time evolution (squeezing) of a pure state, their large occupation number notwithstanding. A nonzero entropy of the gravitons [classical gravitational waves (GW) after decoherence] can be obtained through coarse graining. The latter has to be physically justified and should not contradict observational constraints. We propose two ways of coarse graining for which the fixed temporal phase of each Fourier mode of the GW background still remains observable: one based on quantum entanglement, and another one following from the presence of a secondary GW background. The proposals are shown to be mutually consistent. They lead to the result that the entropy of the primordial GW background is significantly smaller than it was thought earlier. The difference can be ascribed to the information about the regular (inflationary) initial state of the Universe which is stored in this background and which reveals itself, in particular, in the appearance of primordial peaks (acoustic peaks in the case of scalar perturbations) in the multipole spectra of the CMB temperature anisotropy and polarization.