Talk detail

Participant	Olmo, Gonzalo J.
Institution	University of Valencia - CSIC - Depto. Fisica Teorica, C/Dr. Moliner 50 - Burjassot - Valencia - Spain

Session	AT2	Accepted		Order	Time
Talk	Oral abstract	Title	Hybrid f( R) theories, local constraints, and cosmic speedup.
Co-authors
Abstract	I present an extension of general relativity in which an f(R ) term à la Palatini is added to the usual Einstein-Hilbert Lagrangian. Expressing the theory in a dynamically equivalent scalar-tensor form, I show that it can pass the Solar System observational tests even if the scalar field is very light or massless. I provide two simple models which are consistent with local tests and lead to late-time cosmic acceleration.

Session	AT3	Accepted		Order	Time
Talk	Oral abstract	Title	Nonsingular Black Holes in Palatini Extensions of General Relativity
Co-authors
Abstract	I discuss static, spherically symmetric solutions with an electric field (Reissner-Nordstrom black holes) in a quadratic extension of general relativity (GR) formulated in the Palatini approach (assuming that metric and connection are independent fields). Unlike the usual metric formulation of this theory, the field equations are second-order and ghost-free. It is found that the resulting black holes present a central core whose area is proportional to the Planck area times the number of charges. Some of these solutions are nonsingular. In this case, the mass-to-charge ratio implies that the core matter density is independent of the specific amounts of charge and mass and of order the Planck density.