Seminário do Grupo de Física Teórica

Author: Sérgio Jorás (UFRJ)

Title: Stars in modified Gravity Theory

Abstract: According to general relativity (GR), about 95% of our universe if assumed homogeneous and isotropic is made of dark components. Therefore, it is natural to look for corrections from GR to avoid this huge blank. The simplest generalization of GR is the so-called f(R) theory. In the metric approach, it yields fourth-order equations for the metric and, as such, they point out a new degree of freedom. Most of the viable modified theories are equivalent to the standard ΛCDM model in the background when one requires it to pass local tests and fitting of the mass power spectrum. We study a simple generalization of the metric exponential f(R) gravity theory that is cosmologically viable and compatible with solar system tests of gravity. As compared to other viable f(R) theories, its steep dependence on the Ricci scalar R facilitates agreement with structure constraints, opening the possibility of f(R) models with equation-of-state parameter that could be distinguished from a cosmological constant (wde = 1) with future surveys at both background and perturbative levels. 

In the present talk, we investigate the effect of this particular modified theory in relativistic stars, namely the mass- radius diagram, the stable branch and the spatial distribuition of the effective curvature uid in the presence of the so-called chameleon effect.