Enriched Phenomenology in Extended Palatini Theories
Abstract
We show that extended theories of gravity with Lagrangian f(R,R_{\mu\nu}R^{\mu\nu}) in the Palatini formulation possess a phenomenology much richer than the simpler f(R) or f(R_{\mu\nu}R^{\mu\nu}) theories. In fact, we find that the scalars R and Q=R_{\mu\nu}R^{\mu\nu} can be written as algebraic functions of the energy density and pressure of the energy momentum tensor. In the simpler cases of f(R) or f(R_{\mu\nu}R^{\mu\nu}) theories, R and Q are just functions of the trace T of the energy-momentum tensor. As a result, in radiation dominated universes f(R) and f(R_{\mu\nu}R^{\mu\nu}) theories exhibit the same dynamics as general relativity with an effective cosmological constant. This is not the case of f(R,R_{\mu\nu}R^{\mu\nu}) models, in which R=R(\rho,P) and Q=Q(\rho,P) and, therefore, modified dynamics exists even for traceless sources.
Keywords
Cite
@article{arxiv.1002.3920,
title = {Enriched Phenomenology in Extended Palatini Theories},
author = {Gonzalo J. Olmo and Helios Sanchis-Alepuz and Swapnil Tripathi},
journal= {arXiv preprint arXiv:1002.3920},
year = {2010}
}
Comments
3 pages, ws-procs975x65.cls to appear in the Proceedings of 12th Marcel Grossmann Meeting, Paris (France)