Cosmologia na teoria de Visser / Cosmology from the Visser s theory
Márcio Eduardo da Silva Alves
DATA DE PUBLICAÇÃO
The advent of observational cosmology has led us to conclude that only 4% of whole Universe is composed by known matter (baryons). On the other hand 23% comes from a kind of non barionic dark matter. Moreover the cosmic dynamics is almost fully dominated by the so called dark energy (usually considered a kind of fluid), which corresponds to 73% of the energy density of the cosmos. In the last years, a lot of proposals arises in order to explain such a fluid, while many alternative gravitational theories have been developed aiming to lead us to know more about the physics laws. In this work we review a parametric equation of state of such fluids, which imply on models with accelerated expansion where the cosmological constant is a particular case. We then present the gravitational theory proposed by M. Visser. Such alternative theory assumes that the graviton is massive. In his theory, Visser uses a non-dynamic background metric in order to construct a tensor, which is necessary to take in account a massive graviton. In the non-relativistic limit, the potential is non-Newtonian, it is instead Yukawian. Some studies about orbital motions in the solar system (using this kind of potential) give an upper limit to the graviton mass of mg < 10-54 g. Under the radiative regime, massive gravitons produce dispersive gravitational waves and introduce new polarization states which are not found in the GR. So, future detections of gravitational radiation will offer new tests to GR and to the alternative theories of gravity. In particular, our results show the possibility to constrain the graviton mass through a cosmological model that results from this bimetric theory. Although the graviton has an apparently negligible mass, our aim is to show that the theory may lead us to a consistent cosmological model, which explains the current observational data without dark energy (and maybe without dark matter).