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arXiv 1206.4253hep-thastro-ph.CO
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准膨胀子：理论与宇宙学

Quasi-Dilaton: Theory and Cosmology

Guido D'Amico, Gregory Gabadadze, Lam Hui, David Pirtskhalava

备注：
v2: discussion of quadratic perturbations in section 5 modified with more positive outlook. References added
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摘要：

广义相对论（GR），不管有没有物质场，都承认尺度不变理论的自然扩展，需要一个量子。在这里，我们表明，最近制定的大规模GR，最低限度地耦合到物质，具有一个新的全球对称性相关的参考坐标w.r.t.缩放。身体上的这种对称性的场在这里被称为准重子，如果只考虑纯引力，它与普通重子重合，但当存在物质拉格朗日量时，它与普通重子不同。我们研究：（1）大质量GR与准强子的理论一致性;（2）与（近）平坦背景上球对称源观测的一致性;（3）该理论的宇宙学意义。我们发现：（1）准介子理论与大质量GR理论是一致的。(II)Vainshtein机制一般被保留，因为在退耦极限中存在增强的对称性，这将准重子变成第二个伽利略，始终耦合到张量场。(III)与大规模GR不同，存在平坦的FRW解决方案。特别是，我们找到了自加速解并讨论了它们的二次扰动。这些解决方案是可测试的凭借不同的有效牛顿常数，管理哈勃膨胀和结构的增长。

英文摘要：

General Relativity (GR), with or without matter fields, admits a natural extension to a scale invariant theory that requires a dilaton. Here we show that the recently formulated massive GR, minimally coupled to matter, possesses a new global symmetry related to scaling of the reference coordinates w.r.t. the physical ones. The field enforcing this symmetry, dubbed here quasi-dilaton, coincides with an ordinary dilaton if only pure gravity is considered, but differs from it when the matter Lagrangian is present. We study: (1) Theoretical consistency of massive GR with the quasi-dilaton; (2) Consistency with observations for spherically symmetric sources on (nearly) flat backgrounds; (3) Cosmological implications of this theory. We find that: (I) The theory with the quasi-dilaton is as consistent as massive GR is. (II) The Vainshtein mechanism is generically retained, owing to the fact that in the decoupling limit there is an enhanced symmetry, which turns the quasi-dilaton into a second galileon, consistently coupled to a tensor field. (III) Unlike in massive GR, there exist flat FRW solutions. In particular, we find self-accelerated solutions and discuss their quadratic perturbations. These solutions are testable by virtue of the different effective Newton's constants that govern the Hubble expansion and structure growth.

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