Accelerating cosmology in modified gravity with scalar field

Tensor-vector-scalar-modified gravity: from small scale to cosmology.

The impressive success of the standard cosmological model has suggested to many that its ingredients are all that one needs to explain galaxies and their systems. I summarize a number of known problems with this programme. They might signal the failure of standard gravity theory on galaxy scales. The requisite hints as to the alternative gravity theory may lie with the modified Newtonian dynami...

Multiple field scalar-tensor theories of gravity and cosmology.

We consider multiple scalar elds coupled to gravity, with special attention given to twoeld theories. First, the conditions necessary for these theories to meet solar system tests are given. Next, we investigate the cosmological evolution of the elds to see if these conditions can be met. Solutions are found in the dust era, as well as radiation and cosmological constant dominated epochs. The p...

Modified gravity and cosmology

Scalar - tensor gravity in an accelerating universe

We consider scalar-tensor theories of gravity in an accelerating universe. The equations for the background evolution and the perturbations are given in full generality for any parametrization of the Lagrangian, and we stress that apparent singularities are sometimes artifacts of a pathological choice of variables. Adopting a phenomenological viewpoint, i.e., from the observations back to the t...

Interactions in Scalar Field Cosmology

We investigate spatially flat isotropic cosmological models which contain a scalar field with an exponential potential and a perfect fluid with a linear equation of state. We include an interaction term, through which the energy of the scalar field is transferred to the matter fields, consistent with a term that arises from scalar–tensor theory under a conformal transformation and field redefin...