Microscopic and macroscopic behaviors of Palatini modified gravity theories

Introduction to Palatini Theories of Gravity and Nonsingular Cosmologies

Conformal aspects of Palatini approach in Extended Theories of Gravity

Abstract The debate on the physical relevance of conformal transformations can be faced by taking the Palatini approach into account to gravitational theories. We show that conformal transformations are not only a mathematical tool to disentangle gravitational and matter degrees of freedom (passing from the Jordan frame to the Einstein frame) but they acquire a physical meaning considering the ...

Gravitomagnetic effects in Palatini f(R) theories of gravity

We explicitly worked out the orbital effects induced on the trajectory of a test particle by the the weak-field approximation of the Kerr-de Sitter metric, which is a solution of vacuum f(R) field equations, in the Palatini formalism. It results that the node, the pericentre and the mean anomaly undergo secular precessions proportional to k, which is a measure of the non linearity of the theory...

The Palatini formalism for higher-curvature gravity theories

We compare the metric and the Palatini formalism to obtain the Einstein equations in the presence of higher-order curvature corrections that consist of contractions of the Riemann tensor, but not of its derivatives. We find that in general the two formalisms are not equivalent and that the set of solutions of the Palatini equations is a non-trivial subset of the solutions of the metric equation...

Cosmological singularities and modified theories of gravity

We consider perturbative modifications of the Friedmann equations in terms of energy density corresponding to modified theories of gravity proposed as an alternative route to comply with the observed accelerated expansion of the universe. Assuming that the present matter content of the universe is a pressureless fluid, the possible singularities that may arise as the final state of the universe...