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Minimal Theory of Bigravity: construction and cosmology
Journal of Cosmology and Astroparticle Physics ( IF 5.3 ) Pub Date : 2021-04-07 , DOI: 10.1088/1475-7516/2021/04/015
Antonio De Felice 1 , Franois Larrouturou 2 , Shinji Mukohyama 1, 3 , Michele Oliosi 1
Affiliation  

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.



中文翻译:

Bigravity的最小理论:构造和宇宙学

沿着另类引力理论中的极简主义路径,我们构建了“大引力极小理论”(MTBG),这是一个关于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自由度,并且允许对于与 Hassan-Rosen bigravity (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前体理论开始,我们仔细选择额外的约束来消除其中的两个来构建理论。研究 MTBG 的宇宙学,我们发现它容纳了均匀和各向同性背景解的两个不同分支,在壳上等同于 HRBG 中存在的两个分支。然而,MTBG 中的那些分支在微扰级别上与 HRBG 的分支不同,都非常健康,并且没有表现出强耦合问题或鬼影不稳定性。在所谓的自加速分支中,以存在有效宇宙学常数为特征,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学,而其向量扇区与GR中的相同。在这两个分支中,张量扇区都表现出通常的 HRBG 特征:有效质量项和引力子的振荡。因此,MTBG 为 HRBG 中的宇宙学提供了稳定的非线性补全。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学,而其向量扇区与GR中的相同。在这两个分支中,张量扇区都表现出通常的 HRBG 特征:有效质量项和引力子的振荡。因此,MTBG 为 HRBG 中的宇宙学提供了稳定的非线性补全。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学,而其向量扇区与GR中的相同。在这两个分支中,张量扇区都表现出通常的 HRBG 特征:有效质量项和引力子的振荡。因此,MTBG 为 HRBG 中的宇宙学提供了稳定的非线性补全。

更新日期:2021-04-07
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