Cluster number counts can be used to test dark energy models. We investigate dark energy candidates which are coupled to dark matter. We analyze the cluster number counts dependence on the amount of dark matter coupled to dark energy. Further more, we study how dark energy inhomogeneities affect cluster abundances. It is shown that increasing the coupling reduces significantly the cluster numbe...

Bruce A. Bassett, Martin Kunz, David Parkinson and Carlo Ungarelli Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth PO1 2EG, UK Astrophysics, Department of Physics, 1 Keble Road, Oxford University, Oxford OX1 3RH, UK Astronomy Centre, CPES, University of Sussex, Brighton, BN1 9QJ, UK School of Physics and Astronomy, University of Birmingham Edgbaston, Birmingham, B15...

We review the underpinnings of the standard Newton-Einstein theory of gravity, and identifywhere it could possibly go wrong. In particular, we discuss the logical independence from eachother of the general covariance principle, the equivalence principle and the Einstein equations, anddiscuss how to constrain the matter energy-momentum tensor which serves as the source of gravity.<lb...

Observations provide increasingly strong evidence that the universe is accelerating. This revolutionary advance in cosmological observations confronts theoretical cosmology with a tremendous challenge, which it has so far failed to meet. Explanations of cosmic acceleration within the framework of general relativity are plagued by difficulties. General relativistic models are nearly all based on...