Bimetric gravity is cosmologically viable
Abstract
Bimetric theory describes gravitational interactions in the presence of an extra spin-2 field. Previous work has suggested that its cosmological solutions are generically plagued by instabilities. We show that by taking the Planck mass for the second metric, Mf, to be small, these instabilities can be pushed back to unobservably early times. In this limit, the theory approaches general relativity with an effective cosmological constant which is, remarkably, determined by the spin-2 interaction scale. This provides a late-time expansion history which is extremely close to ΛCDM, but with a technically-natural value for the cosmological constant. We find Mf should be no larger than the electroweak scale in order for cosmological perturbations to be stable by big-bang nucleosynthesis. We further show that in this limit the helicity-0 mode is no longer strongly-coupled at low energy scales.
- Publication:
-
Physics Letters B
- Pub Date:
- September 2015
- DOI:
- 10.1016/j.physletb.2015.06.062
- arXiv:
- arXiv:1503.07521
- Bibcode:
- 2015PhLB..748...37A
- Keywords:
-
- Modified gravity;
- Massive gravity;
- Background cosmology;
- Cosmic acceleration;
- Dark energy;
- Bimetric gravity;
- Bigravity;
- General Relativity and Quantum Cosmology;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- High Energy Physics - Theory
- E-Print:
- 8+2 pages, 2 tables. Version published in PLB. Minor typo corrections from v3