Book reviews

AIP Conference Proceedings

2008

We summarize several aspects of recent work on quantum stress tensor fluctuations and their role in driving fluctuations of the gravitational field. The role of correlations and anticorrelations is emphasized. We begin with a review of the properties of the stress tensor correlation function. We next consider some illuminating examples of non-gravitational effects of stress tensors fluctuations, specifically fluctuations of the Casimir force and radiation pressure fluctuations. We next discuss passive fluctuations of spacetime geometry and some of their operational signatures. These include luminosity fluctuations, line broadening, and angular blurring of a source viewed through a fluctuating gravitational field. Finally, we discuss the possible role of quantum stress tensor fluctuations in the early universe, especially in inflation. The fluctuations of the expansion of a congruence of comoving geodesics grows during the inflationary era, due to non-cancellation of anticorrelations that would have occurred in flat spacetime. This results in subsequent non-Gaussian density perturbations and allows one to infer an upper bound on the duration of inflation. This bound is consistent with adequate inflation to solve the horizon and flatness problems.

Section: Discussionmentioning

confidence: 99%

“…A preliminary account of this work was summarized in Ref. [23]. The function P ( T ) is asymmetric, as typically odd moments such as T 3 are nonzero.…”

Section: Anticorrelations and The Probability Distributionmentioning

confidence: 99%

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Quantum Stress Tensor Fluctuations and their Physical Effects

AIP Conference Proceedings

2008

“…Quantum fluctuations of the stress tensor operator have been studied in numerous recent papers [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19]. Fluctuations of the stress tensor drive passive fluctuations of the gravitational field, which are to be distinguished from the active fluctuations due to the quantization of the gravitational degrees of freedom.…”

Section: Introductionmentioning

confidence: 99%

Possible constraints on the duration of inflationary expansion from quantum stress tensor fluctuations

2007

Phys. Rev. D

We discuss the effect of quantum stress tensor fluctuations in deSitter spacetime upon the expansion of a congruence of timelike geodesics. We treat a model in which the expansion fluctuations begin on a given hypersurface in deSitter spacetime, and find that this effect tends to grow, in contrast to the situation in flat spacetime. This growth potentially leads to observable consequences in inflationary cosmology in the form of density perturbations which depend upon the duration of the inflationary period. In the context of our model, the effect may be used to place upper bounds on this duration.

“…We may use the results of Ref. [27], where the electromagnetic field stress tensor correlation function was shown to be…”

Section: Appendix A: Flat Space Stress Tensor Correlation Functionsmentioning

confidence: 99%

Gravity waves from quantum stress tensor fluctuations in inflation

Hsiang

et al. 2011

Phys. Rev. D

We consider the effects of the quantum stress tensor fluctuations of a conformal field in generating gravity waves in inflationary models. We find a non-scale invariant, non-Gaussian contribution which depends upon the total expansion factor between an initial time and the end of inflation.This spectrum of gravity wave perturbations is an illustration of a negative power spectrum, which is possible in quantum field theory. We discuss possible choices for the initial conditions. If the initial time is taken to be sufficiently early, the fluctuating gravity waves are potentially observable both in the CMB radiation and in gravity wave detectors, and could offer a probe of transplanckian physics. The fact that they have not yet been observed might be used to constrain the duration and energy scale of inflation. However, this conclusion is contingent upon including the contribution of modes which were transplanckian at the beginning of inflation.