Matter may matter
Abstract
We propose a gravitational theory in which the effective Lagrangian of the gravitational field is given by an arbitrary function of the Ricci scalar, the trace of the matter energymomentum tensor, and the contraction of the Ricci tensor with the matter energymomentum tensor. The matter energymomentum tensor is generally not conserved, thus leading to the appearance of an extraforce, acting on massive particles in a gravitational field. The stability conditions of the theory with respect to local perturbations are also obtained. The cosmological implications of the theory are investigated, representing an exponential solution. Hence, a Ricci tensorenergymomentum tensor coupling may explain the recent acceleration of the universe, without resorting to the mysterious dark energy.
 Publication:

International Journal of Modern Physics D
 Pub Date:
 October 2014
 DOI:
 10.1142/S0218271814420164
 arXiv:
 arXiv:1405.3771
 Bibcode:
 2014IJMPD..2342016H
 Keywords:

 Modified gravity;
 cosmology;
 extra force;
 04.50.Kd;
 04.20.Cv;
 Modified theories of gravity;
 Fundamental problems and general formalism;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Theory
 EPrint:
 Received an "Honorable Mention" in the Gravity Research Foundation Essay Contest 2014