Bigravitational inflation

Abstract

We study the realization of cosmic inflation in bigravity theories. By analyzing the evolution of scalar, vector, and tensor perturbations in de Sitter-like spacetimes, we find strong stability constraints on the class of viable vacua offered by these theories. More specifically, the only stable de Sitter vacua contain two nondecoupled gravitons (one of which is massive) with different maximal propagation speeds. We derive an effective theory for the massless graviton, which is found to propagate at an intermediate speed, limited by the two maximal values. For inflation, while the spectrum of density perturbations remains nearly scale invariant, the power spectrum of tensor modes is found to depart from the usual prediction found in standard slow-roll inflation. In particular, both the tensor to scalar ratio $r$ and the spectral index of tensor modes $n_T$ receive sizable contributions from the couplings of the theory, leading to specific signals that may be tested in future cosmological probes of CMB polarization.

5 pages, v2: discussion changed, published version

References in corpus (10)

• Cosmological Constraints from the SDSS Luminous Red Galaxies
• The Effective Field Theory of Inflation
• Effective Field Theory for Inflation
• CMBPol Mission Concept Study: Probing Inflation with CMB Polarization
• ACTPol: A polarization-sensitive receiver for the Atacama Cosmology Telescope
• Mass hierarchies and non-decoupling in multi-scalar field dynamics
• New Sources of Gravitational Waves during Inflation
• Eddington-Born-Infeld gravity and the large scale structure of the Universe
• A note on bigravity and dark matter
• The Parameterised Post-Newtonian Limit of Bimetric Theories of Gravity

Cited by in corpus (3)

• On the importance of heavy fields during inflation
• Effective field theory of weakly coupled inflationary models
• Massive cosmological scalar perturbations