The Effects of Stress Tensor Fluctuations upon Focusing

TL;DR

This paper investigates how quantum stress tensor fluctuations influence gravitational focusing, leading to observable effects like angular blurring and luminosity fluctuations in distant sources, using a Langevin equation approach.

Contribution

It introduces an operational method to quantify gravitational effects of quantum stress tensor fluctuations on geodesic focusing.

Findings

Explicit calculations for a scalar field in a thermal state.

Demonstrates fluctuations cause observable image blurring.

Provides a framework for analyzing quantum gravitational effects.

Abstract

We treat the gravitational effects of quantum stress tensor fluctuations. An operational approach is adopted in which these fluctuations produce fluctuations in the focusing of a bundle of geodesics. This can be calculated explicitly using the Raychaudhuri equation as a Langevin equation. The physical manifestation of these fluctuations are angular blurring and luminosity fluctuations of the images of distant sources. We give explicit results for the case of a scalar field on a flat background in a thermal state.