Astronomy and Astrophysics – Astrophysics – General Relativity and Quantum Cosmology
Scientific paper
2009-04-21
Phys.Rev.D81:043006,2010
Astronomy and Astrophysics
Astrophysics
General Relativity and Quantum Cosmology
24 pages in preprint style; v6: published version
Scientific paper
10.1103/PhysRevD.81.043006
It has been suggested recently to study the dynamics of a gravitating gluon condensate q in the context of a spatially flat Friedmann-Robertson-Walker universe. The expansion of the Universe (or, more generally, the presence of a nonvanishing Ricci curvature scalar R) perturbs the gluon condensate and may induce a nonanalytic term \tilde{h}(R,q) in the effective gravitational action. The aim of this article is to explore the cosmological implications of a particular nonanalytic term \tilde{h} \propto \eta |R|^{1/2} |q|^{3/4}. With a quadratic approximation of the gravitating gluon-condensate vacuum energy density \rho_{V}(q) near the equilibrium value q_{0} and a small coupling constant \eta of the modified-gravity term \tilde{h}, an "accelerating universe" is obtained which resembles the present Universe, both qualitatively and quantitatively. The unknown component X of this model universe (here, primarily due to modified-gravity effects) has an effective equation-of-state parameter \bar{w}_{X} which is found to evolve toward the value -1 from above.
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