$R + R^2$ Gravity as $R +$ Backreaction

Details $R + R^2$ Gravity as $R +$ Backreaction $R + R^2$ Gravity as $R +$ Backreaction

1995-09-30

arxiv.org/abs/gr-qc/9509058v1

Phys.Rev. D52 (1995) 6922-6928

Astronomy and Astrophysics

Astrophysics

General Relativity and Quantum Cosmology

Accepted for publication in Phy. Rev. D.,18 pages, 6 figures, Latex file

Scientific paper

10.1103/PhysRevD.52.6922

Quadratic theory of gravity is a complicated constraint system. We investigate some consequences of treating quadratic terms perturbatively (higher derivative version of backreaction effects). This approach is shown to overcome some well known problems associated with higher derivative theories, i.e., the physical gravitational degree of freedom remains unchanged from those of Einstein gravity. Using such an interpretation of $R + \beta R^2$ gravity, we investigate a classical and Wheeler DeWitt evolution of $R + \beta R^2$ gravity for a particular sign of $\beta$, corresponding to non- tachyon case. Matter is described by a phenomenological $\rho \propto a(t)^{-n}$. It is concluded that both the Friedmann potential $U(a)$ ($ {\dot a}^2 + 2U(a) = 0 $) and the Wheeler DeWitt potential $W(a)$ ($\left[-{\partial^2\over \partial a^2} + 2W(a)\right]\psi (a) =0 $) develop repulsive barriers near $a\approx 0$ for $n>4$ (i.e., $ p > {1\over 3}\rho $). The interpretations is clear. Repulsive barrier in $U(a)$ implies that a contracting FRW universe ($k>0, k=0, k<0$) will bounce to an expansion phase without a total gravitational collapse. Repulsive barrier in $W(a)$ means that $a \approx 0$ is a classically forbidden region. Therefore, probability of finding a universe with the big bang singularity ($a=0$ ) is exponentially suppressed.

Affiliated with

Also associated with

No associations

Rating

$R + R^2$ Gravity as $R +$ Backreaction does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with $R + R^2$ Gravity as $R +$ Backreaction, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and $R + R^2$ Gravity as $R +$ Backreaction will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-251917