Cosmological evolution in bimetric gravity: observational constraints and LSS signatures

Bimetric gravity is an interesting alternative to standard GR given its potential to provide a concrete theoretical framework for a ghost-free massive gravity theory. Here we investigate a class of Bimetric gravity models for their cosmological implications. We study the background expansion as well as the growth of matter perturbations at linear and second order. We use low-redshift observations from SnIa (Pantheon+ and SH0ES), Baryon Acoustic Oscillations (BAO), the growth ( fσ ₈ fσ8 ) measurements and the measurement from Megamaser Cosmology Project to constrain the Bimetric model. We find that the Bimetric models are consistent with the present data alongside the Λ Λ CDM model. We reconstructed the “ effective dark energy equation of state”( ω de ωde ) and “Skewness”( S₃ S3 ) parameters for the Bimetric model from the observational constraints and show that the current low-redshift data allow significant deviations in ω de ωde and S₃ S3 parameters with respect to the Λ Λ CDM behaviour. We also look at the ISW effect via galaxy-temperature correlations and find that the best fit Bimetric model behaves similarly to Λ Λ CDM in this regard.