Cosmology in bimetric theory with an effective composite coupling to matter
- School of Mathematical Sciences, University of Nottingham, University Park, Nottingham, NG7 2RD (United Kingdom)
- Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, 10691 Stockholm (Sweden)
- Yukawa Institute for Theoretical Physics, Kyoto University, Kyoto 606-8502 (Japan)
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA (United Kingdom)
We study the cosmology of bimetric theory with a composite matter coupling. We find two possible branches of background evolution. We investigate the question of stability of cosmological perturbations. For the tensor and vector perturbations, we derive conditions on the absence of ghost and gradient instabilities. For the scalar modes, we obtain conditions for avoiding ghost degrees. In the first branch, we find that one of the scalar modes becomes a ghost at the late stages of the evolution. Conversely, this problem can be avoided in the second branch. However, we also find that the constraint for the second branch prevents the doubly coupled matter fields from being the standard ingredients of cosmology. We thus conclude that a realistic and stable cosmological model requires additional minimally coupled matter fields.
- OSTI ID:
- 22525906
- Journal Information:
- Journal of Cosmology and Astroparticle Physics, Journal Name: Journal of Cosmology and Astroparticle Physics Journal Issue: 04 Vol. 2015; ISSN 1475-7516
- Country of Publication:
- United States
- Language:
- English
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