Minimal Theory of Bigravity: construction and cosmology
Minimal Theory of Bigravity: construction and cosmology
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DOI：
10.1088/1475-7516/2021/04/015
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发表时间：
2020-12
影响因子：
6.4
通讯作者：
Antonio De Felice;F. Larrouturou;S. Mukohyama;Michele Oliosi
中科院分区：
文献类型：
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作者：
Antonio De Felice;F. Larrouturou;S. Mukohyama;Michele Oliosi
遵循引力理论中的极简主义路径，我们构建了“最小双引力理论”（MTBG），这是一种两个相互作用的自旋2场的理论，它只传播四个局部自由度，而不是通常的七个，并且允许与哈桑-罗森双引力（HRBG）中相同的均匀和各向同性宇宙学解。从传播六个局部自由度的先驱理论开始，我们仔细选择额外的约束，以消除其中两个来构建理论。调查宇宙学的MTBG，我们发现，它可以容纳两个不同的分支均匀和各向同性的背景解决方案，相当于壳的两个分支，是目前在HRBG。然而，MTBG中的这些分支在微扰水平上不同于HRBG中的分支，它们都是完全健康的，并且不表现出强耦合问题，也没有鬼不稳定性。在所谓的自加速分支中，其特征是存在一个有效的宇宙常数，标量和矢量扇区与广义相对论（GR）中的相同。在所谓的正常分支中，标量扇区表现出非平凡的现象，而其矢量扇区保持与GR中相同。在这两个分支中，张量扇区表现出通常的HRBG特征：有效质量项和引力子的振荡。因此，MTBG提供了一个稳定的非线性宇宙学在HRBG完成。
Following the path of minimalism in alternative theories of gravity, we construct the “Minimal Theory of Bigravity” (MTBG), a theory of two interacting spin-2 fields that propagates only four local degrees of freedom instead of the usual seven ones and that allows for the same homogeneous and isotropic cosmological solutions as in Hassan-Rosen bigravity (HRBG). Starting from a precursor theory that propagates six local degrees of freedom, we carefully choose additional constraints to eliminate two of them to construct the theory. Investigating the cosmology of MTBG, we find that it accommodates two different branches of homogeneous and isotropic background solutions, equivalent on-shell to the two branches that are present in HRBG. Those branches in MTBG differ however from the HRBG ones at the perturbative level, are both perfectly healthy and do not exhibit strong coupling issues nor ghost instabilities. In the so-called self-accelerating branch, characterized by the presence of an effective cosmological constant, the scalar and vector sectors are the same as in General Relativity (GR). In the so-called normal branch, the scalar sector exhibits non-trivial phenomenology, while its vector sector remains the same as in GR. In both branches, the tensor sector exhibits the usual HRBG features: an effective mass term and oscillations of the gravitons. Therefore MTBG provides a stable nonlinear completion of the cosmology in HRBG.