Cyclic cosmology from Lagrange-multiplier modified gravity

Modified gravity and cosmology

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...

Non-singular Cosmology in Modified Gravity

A non-singular cosmology is derived in modified gravity (MOG). The universe begins in the distant past in a contracting de Sitter phase, is non-singular at t = 0 and then describes approximately the standard radiation dominated solution before the time of decoupling. The spacetime in the neighborhood of t = 0 is described by Minkowski spacetime in which the Weyl curvature tensor vanishes and th...

Inflationary Cosmology in Modified Gravity Theories

We review inflationary cosmology in modified gravity such as R gravity with its extensions in order to generalize the Starobinsky inflation model. In particular, we explore inflation realized by three kinds of effects: modification of gravity, the quantum anomaly, and the R term in loop quantum cosmology. It is explicitly demonstrated that in these inflationary models, the spectral index of sca...

Cuscuton Cosmology: Dark Energy meets Modified Gravity

In a companion paper [1], we have introduced a model of scalar field dark energy, Cuscuton, which can be realized as the incompressible (or infinite speed of sound) limit of a k-essence fluid. In this paper, we study how Cuscuton modifies the constraint sector of Einstein gravity. In particular, we study Cuscuton cosmology and show that even though Cuscuton can have an arbitrary equation of sta...