Markkanen T
1Department of Physics, Imperial College London, London, SW7 2AZ UK.
2Department of Physics, King's College London, Strand, London, WC2R 2LS UK.
Eur Phys J C Part Fields. 2018;78(2):97. doi: 10.1140/epjc/s10052-018-5575-9. Epub 2018 Feb 2.
We present a 4-dimensional back reaction analysis of de Sitter space for a conformally coupled scalar field in the presence of vacuum energy initialized in the Bunch-Davies vacuum. In contrast to the usual semi-classical prescription, as the source term in the Friedmann equations we use expectation values where the unobservable information hidden by the cosmological event horizon has been neglected i.e. coarse grained over. It is shown that in this approach the energy-momentum is precisely thermal with constant temperature despite the dilution from the expansion of space due to a flux of energy radiated from the horizon. This leads to a self-consistent solution for the Hubble rate, which is gradually evolving and at late times deviates significantly from de Sitter. Our results hence imply de Sitter space to be unstable in this prescription. The solution also suggests dynamical vacuum energy: the continuous flux of energy is balanced by the generation of negative vacuum energy, which accumulatively decreases the overall contribution. Finally, we show that our results admit a thermodynamic interpretation which provides a simple alternate derivation of the mechanism. For very long times the solutions coincide with flat space.
我们针对在邦奇 - 戴维斯真空中初始化的真空能量存在情况下的共形耦合标量场，给出了德西特空间的四维反作用分析。与通常的半经典方法不同，作为弗里德曼方程中的源项，我们使用期望值，其中被宇宙学事件视界隐藏的不可观测信息已被忽略，即进行了粗粒化处理。结果表明，在这种方法中，尽管由于从视界辐射出的能量通量导致空间膨胀产生稀释效应，但能量 - 动量精确地处于恒定温度的热状态。这导致了哈勃率的自洽解，该解在逐渐演化，并且在后期显著偏离德西特空间。因此，我们的结果意味着在这种设定下德西特空间是不稳定的。该解还暗示了动态真空能量：能量的连续通量由负真空能量的产生来平衡，这累积地降低了总体贡献。最后，我们表明我们的结果允许一种热力学解释，它为该机制提供了一种简单的替代推导。在很长时间内，这些解与平坦空间一致。
