标量-张量引力理论中的涌现宇宙膨胀

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. 我们考虑标量-张量引力理论中大尺度宇宙膨胀的涌现。通过将时空的亚尺度区域建模为围绕Minkowski空间的弱场展开，然后将许多此类区域连接起来以创建统计上均匀和各向同性的宇宙学。我们发现，当标量场可以被视为扰动时，涌现出的宇宙行为可由该理论的Friedmann解良好地建模。当发生非扰动屏蔽机制时，这一结果不再成立。在标量场受制于鲁温机制的情况下，我们发现与预期Friedmann行为存在显著偏差。特别是，屏蔽质量不再贡献于Klein-Gordon方程中，这抑制了偏离广义相对论行为的偏差。