The reliability horizon for semi-classical quantum gravity: Metric fluctuations are often more important than back-reaction
Abstract
In this note I introduce the notion of the ``reliability horizon'' for semi-classical quantum gravity. This reliability horizon is an attempt to quantify the extent to which we should trust semi-classical quantum gravity, and to get a better handle on just where the Planck regime resides. I point out that the key obstruction to pushing semi-classical quantum gravity into the Planck regime is often the existence of large metric fluctuations, rather than a large back-reaction. There are many situations where the metric fluctuations become large long before the back-reaction is significant. Issues of this type are fundamental to any attempt at proving Hawking's chronology protection conjecture from first principles, since I shall prove that the onset of chronology violation is always hidden behind the reliability horizon.
Keywords
Cite
@article{arxiv.gr-qc/9702041,
title = {The reliability horizon for semi-classical quantum gravity: Metric fluctuations are often more important than back-reaction},
author = {Matt Visser},
journal= {arXiv preprint arXiv:gr-qc/9702041},
year = {2009}
}
Comments
6 pages; ReV_TeX 3.0; two-column format. Revisions: Central definitions and results essentially unchanged. Discussion of the relationship between this letter and the Kay-Radzikowski-Wald singularity theorems greatly extended and clarified. Discussion of reliability horizon near curvature singularities modified. Several references added. Minor typos fixed. Technical TeX modifications