Physics
Scientific paper
Aug 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011phrvd..84d8501h&link_type=abstract
Physical Review D, vol. 84, Issue 4, id. 048501
Physics
1
Quantum Field Theory In Curved Spacetime, Dark Energy, Cosmology
Scientific paper
There are two nonequivalent ways to check if quantum effects in the context of semiclassical gravity can moderate or even cancel the final singularity appearing in a universe filled with dark energy: The method followed in [J. D. Bates and P. R. Anderson, Phys. Rev. DPRVDAQ1550-7998 82, 024018 (2010).10.1103/PhysRevD.82.024018] is to introduce the classical Friedmann solution in the energy density of the quantum field, and to compare the result with the density of dark energy determined by the Friedmann equation. The method followed in this comment is to solve directly the semiclassical equations. The results obtained by either method are very different, leading to opposed conclusions. The authors of [J. D. Bates and P. R. Anderson, Phys. Rev. DPRVDAQ1550-7998 82, 024018 (2010)10.1103/PhysRevD.82.024018] find that for a perfect fluid with state equation p=ωρ and ω<-1 (phantom fluid), considering realistic values of ω leads to a quantum field energy density that remains small compared to the dark energy density until the curvature reaches the Planck scale or higher, at which point the semiclassical approach stops being valid. The conclusion is that quantum effects do not affect significantly the expansion of the universe until the scalar curvature reaches the Planck scale. In this comment we will show by numerical integration of the semiclassical equations that quantum effects modify drastically the expansion of the universe from an early point. We also present an analytic argument explaining why the method of [J. D. Bates and P. R. Anderson, Phys. Rev. DPRVDAQ1550-7998 82, 024018 (2010)10.1103/PhysRevD.82.024018] fails to detect this. The units employed are the same as in [J. D. Bates and P. R. Anderson, Phys. Rev. DPRVDAQ1550-7998 82, 024018 (2010)10.1103/PhysRevD.82.024018] (c=ℏ=G=1).
Amoros Jaume
Haro Jaume
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