Physics
Scientific paper
Jun 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aipc.1241..534c&link_type=abstract
INVISIBLE UNIVERSE: Proceedings of the Conference. AIP Conference Proceedings, Volume 1241, pp. 534-542 (2010).
Physics
Cosmology, Dark Matter, Gravitational Waves, Gamma-Rays, Origin And Formation Of The Universe, Dark Matter, Gravitational Fields, Gamma-Ray Sources, Gamma-Ray Bursts
Scientific paper
In an attempt to look for a viable mechanism leading to a present day accelerated expansion, we investigate the possibility that the observed cosmic speed up may be recovered in the framework of the Rastall's theory, relying on the non - conservativity of the stress - energy tensor, i.e. Tνμμ≠0. We derive the modified Friedmann equations and show that they correspond to Cardassian-like equations. We also show that, under suitable assumptions on the equation of state of the matter term sourcing the gravitational field, it is indeed possible to get an accelerated expansion, in agreement with the Hubble diagram of both Type Ia Supernovae (SNeIa) and Gamma Ray Bursts (GRBs). Unfortunately, to achieve such a result one has to postulate a matter density parameter much larger than the typical ΩM~=0.3 value inferred from cluster gas mass fraction data. As a further issue, we then discuss the possibility to retrieve the Rastall's theory from a Palatini variational principle approach to f(R) gravity. However, such an attempt turns out to be unsuccessful.
Capone Monica
Cardone Vincenzo Fabrizio
Luca Ruggiero Matteo
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