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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
On the non-attractive character of gravity in f(R) theories
Journal of Cosmology and Astroparticle Physics, Volume 2013, No. 7, Article 009, Year 2013
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Description
In General Relativity without a cosmological constant a non-positive contribution from the space-time geometry to Raychaudhuri equation is found provided that particular energy conditions are assumed and regardless the considered solution of the Einstein's equations. This fact is usually interpreted as a manifestation of the attractive character of gravity. Nevertheless, a positive contribution to Raychaudhuri equation from space-time geometry should occur since this is the case in an accelerated expanding Robertson-Walker model for congruences followed by fundamental observers. Modified gravity theories provide the possibility of a positive contribution although the standard energy conditions are assumed. We address this important issue in the context of f(R) theories, deriving explicit upper bounds for the contribution of space-time geometry to the Raychaudhuri equation. Then, we examine the parameter constraints for some paradigmatic f(R) models in order to ensure a positive contribution to this equation. Furthermore, we consider the implications of these upper bounds in the equivalent formulation of f(R) theories as a Brans-Dicke model. © 2013 IOP Publishing Ltd and Sissa Medialab srl.
Authors & Co-Authors
Albareti, Franco D.
Spain, Madrid
Universidad Complutense de Madrid
Cembranos, Jose A.R.
Spain, Madrid
Universidad Complutense de Madrid
Cruz-Dombriz, Álvaro De La
Spain, Madrid
Consejo Superior de Investigaciones Científicas
South Africa, Cape Town
University of Cape Town
Dobado, Antonio
Spain, Madrid
Universidad Complutense de Madrid
Statistics
Citations: 4
Authors: 4
Affiliations: 3
Identifiers
Doi:
10.1088/1475-7516/2013/07/009
e-ISSN:
14757516