Accelerating cosmology in modified gravity: From convenient F(R) or string-inspired theory to bimetric F(R) gravity

Self-accelerating Massive Gravity: Bimetric Determinant Singularities

Pierre Gratia,1, ∗ Wayne Hu,2, † and Mark Wyman2, 3, ‡ Department of Physics, University of Chicago, Chicago, Illinois 60637, U.S.A. Kavli Institute for Cosmological Physics, Department of Astronomy & Astrophysics, Enrico Fermi Institute, University of Chicago, Chicago, Illinois 60637, U.S.A. Center for Cosmology and Particle Physics, Department of Physics, New York University, New York, NY, 10...

Modified gravity and cosmology

Bimetric Models of Gravity and Cosmology in the Early Universe

In the last decades, we have witnessed an astonishing progress in our understanding of the Early Universe and its evolution into the actual con guration we observe. General Relativity has been a key ingredient for this achievement, and it certainly provides the correct way to couple matter elds to gravity. However, in other fundamental theories (string theory, for example), we can nd an immense...

String-Inspired Gravity through Symmetries

We study a string-inspired cosmological model from the symmetries point of view. We start by deducing the form that each physical quantity must take so that the field equations, in the string frame, admit self-similar solutions. In the same way, we formalize the use of power-law solutions (less restrictive than the self-similar ones) by studying the wave equation for the dilaton through the Lie...

Fluctuation Spectrum from a Scalar-Tensor Bimetric Gravity Theory

Predictions of the CMB spectrum from a bimetric gravity theory (BGT) [1] are presented. The initial inflationary period in BGT is driven by a vanishingly small speed of gravitational waves vg in the very early universe. This initial inflationary period is insensitive to the choice of scalar field potential and initial values of the scalar field. After this initial period of inflation, vg will i...