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Title: Viable cosmology in bimetric theory

We study cosmological perturbations in bimetric theory with two fluids each of which is coupled to one of the two metrics. Focusing on a healthy branch of background solutions, we clarify the stability of the cosmological perturbations. For this purpose, we extend the condition for the absence of the so-called Higuchi ghost, and show that the condition is guaranteed to be satisfied on the healthy branch. We also calculate the squared propagation speeds of perturbations and derive the conditions for the absence of the gradient instability. To avoid the gradient instability, we find that the model parameters are weakly constrained.
Authors:
 [1] ;  [2] ; ;  [3] ;  [4]
  1. Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)
  2. School of Mathematical Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom)
  3. Kavli Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, University of Tokyo (WPI), 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583 (Japan)
  4. Department of Physics, Kyoto University, Kyoto 606-8502 (Japan)
Publication Date:
OSTI Identifier:
22373507
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Cosmology and Astroparticle Physics; Journal Volume: 2014; Journal Issue: 06; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; COSMOLOGY; FOCUSING; INSTABILITY; MATHEMATICAL SOLUTIONS; METRICS; PERTURBATION THEORY; STABILITY; VELOCITY