gravity and Cardassian-like expansion as one of its consequences
Department of Physics, Boğaziçi University, Bebek Istanbul, Turkey
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Revised: 13 June 2014
Accepted: 1 July 2014
Published online: 4 August 2014
We propose a new model of gravity where the Ricci scalar in the Einstein-Hilbert action is replaced by an arbitrary function of and of the norm of energy-momentum tensor, i.e., . Field equations are derived in the metric formalism. We find that the equation of motion of massive test particles is non-geodesic and these test particles are acted upon by a force which is orthogonal to the four-velocity of the particles. We also find the Newtonian limit of the model to calculate the extra acceleration which can affect the perihelion of Mercury. There is a deviation from the general relativistic (GR) result unless the energy density of fluid is constant. Arranging the parameter gives an opportunity to cure the inconsistency between the observational values for the abundance of light elements and the standard Big Bang nucleosynthesis results. Even the dust-dominated universe undergoes an accelerated expansion without using a cosmological constant in Model II. With this specific choice of , we get Cardassian-like expansion.
© Società Italiana di Fisica and Springer-Verlag Berlin Heidelberg, 2014