GROWTH INDEX AND MODIFIED GRAVITY

Constraining Modified Gravity and Growth with Weak Lensing ⋆

The idea that we live in a Universe undergoing a period of acceleration is a new, yet strongly held, notion in cosmology. As this can, potentially, be explained with a modification to General Relativity we look at current cosmological data with the purpose of testing aspects of gravity. Firstly we constrain a phenomenological model (mDGP) motivated by a possible extra dimension. This is charact...

Modified gravity and cosmology

Dark Energy and Modified Gravity

Explanations of the late-time cosmic acceleration within the framework of general relativity are plagued by difficulties. General relativistic models are mostly based on a dark energy field with fine-tuned, unnatural properties. There is a great variety of models, but all share one feature in common – an inability to account for the gravitational properties of the vacuum energy, and a failure t...

Stealth Acceleration and Modified Gravity

We show how to construct consistent braneworld models which exhibit late time acceleration. Unlike self-acceleration, which has a de Sitter vacuum state, our models have the standard Minkowski vacuum and accelerate only in the presence of matter, which we dub “stealth-acceleration”. We use an effective action for the brane which includes an induced gravity term, and allow for an asymmetric set-...

Cosmic Acceleration and Modified Gravity

Abstract I briefly discuss some attempts to construct a consistent modification to General Relativity (GR) that might explain the observed late-time acceleration of the universe and provide an alternative to dark energy. I mention the issues facing extensions to GR, illustrate these with two specific examples, and discuss the resulting observational and theoretical obstacles. This article compr...