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Bimetric gravity is cosmologically viable

By Sweden SE-10691 Stockholm Roslagstullsbacken 23 Stockholm University KTH Royal Institute of Technology YasharNordita Akrami, Sweden) SE-10691 Stockholm Roslagstullsbacken 23 Stockholm University KTH Royal Institute of Technology S.F.(Nordita Hassan, Sweden) SE-10691 Stockholm Roslagstullsbacken 23 Stockholm University KTH Royal Institute of Technology Frank(Nordita Könnig, Sweden) SE-10691 Stockholm Roslagstullsbacken 23 Stockholm University KTH Royal Institute of Technology Angnis(Nordita Schmidt-May and Sweden) SE-10691 Stockholm Roslagstullsbacken 23 Stockholm University KTH Royal Institute of Technology Adam R.(Nordita Solomon

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

Year: 2015
DOI identifier: 10.1016/j.physletb.2015.06.062
OAI identifier: oai:www.openaccessrepository.it:12019

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