We consider the emergence of large-scale cosmological expansion in scalar–tensor theories of gravity. This is achieved by modelling sub-horizon regions of space-time as weak-field expansions around Minkowski space, and then subsequently joining many such regions together to create a statistically homogeneous and isotropic cosmology. We find that when the scalar field can be treated perturbatively, the cosmological behaviour that emerges is well modelled by the Friedmann solutions of the theory. When non-perturbative screening mechanisms occur this result no longer holds, and in the case of scalar fields subject to the chameleon mechanism we find significant deviations from the expected Friedmann behaviour. In particular, the screened mass no longer contributes to the Klein–Gordon equation, suppressing deviations from general relativistic behaviour.

中文翻译：

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引力标量-张量理论中的涌现宇宙学膨胀


我们考虑了标量-张量引力理论中大规模宇宙学膨胀的出现。这是通过将时空的亚视界区域建模为闵可夫斯基空间周围的弱场膨胀，然后将许多此类区域连接在一起以创建统计上均匀和各向同性的宇宙学来实现的。我们发现，当标量场可以被扰动地处理时，出现的宇宙学行为就可以很好地由该理论的弗里德曼解建模。当非扰动筛选机制发生时，这个结果不再成立，在受变色龙机制约束的标量场的情况下，我们发现与预期的弗里德曼行为有很大偏差。特别是，筛选的质量不再对 Klein-Gordon 方程做出贡献，从而抑制了与广义相对论行为的偏差。