2015/01/31 by D. Comelli, Denis Comelli, Marco Crisostomi +4 · 2 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #Classical mechanics #Cosmological perturbation theory #Cosmology #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #Gravitation #Graviton #Instability #Massive gravity #Mathematical physics #Perturbation (astronomy) #Physics #Quantum mechanics #Scalar (mathematics) #Scale invariance #Tensor (intrinsic definition) #Theoretical physics #astro-ph.CO #gr-qc #hep-th
paper · pdf · doi:10.1088/1475-7516/2015/04/026
published as JCAP04(2015)026 · 20 pages, 1 figure, references added
openalex publication_date 2015/04/20 · arxiv created 2015/04/21 · arxiv updated 2015/04/22 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
We study cosmology in the bigravity formulation of the dRGT model where matter couples to both metrics. At linear order in perturbation theory two mass scales emerge: an hard one from the dRGT potential, and an environmental dependent one from the coupling of bigravity with matter. At early time, the dynamics is dictated by the second mass scale which is of order of the Hubble scale. The set of gauge invariant perturbations that couples to matter follow closely the same behaviour as in GR . The remaining perturbations show no issue in the scalar sector, while problems arise in the tensor and vector sectors. During radiation domination, a tensor mode grows power-like at super-horizon scales. More dangerously, the only propagating vector mode features an exponential instability on sub-horizon scales. We discuss the consequences of such instabilities and speculate on possible ways to deal with them.