Vacuum Fluctuations and the Small Scale Structure of Spacetime

TL;DR

This paper demonstrates that vacuum fluctuations in a 2D dilaton gravity model cause extreme focusing of light cones at small scales, potentially explaining quantum gravity phenomena like dimensional reduction.

Contribution

It introduces the concept of asymptotic silence caused by vacuum fluctuations, linking it to quantum gravity features in a simplified 2D model with implications for 4D.

Findings

Vacuum fluctuations cause sharp light cone focusing near the Planck scale.

The phenomenon suggests a breakdown of spacetime into causally disconnected regions.

Potential explanation for dimensional reduction in quantum gravity.

Abstract

We show that vacuum fluctuations of the stress-energy tensor in two-dimensional dilaton gravity lead to a sharp focusing of light cones near the Planck scale, effectively breaking space up into a large number of causally disconnected regions. This phenomenon, called "asymptotic silence" when it occurs in cosmology, might help explain several puzzling features of quantum gravity, including evidence of spontaneous dimensional reduction at short distances. While our analysis focuses on a simplified two-dimensional model, we argue that the qualitative features should still be present in four dimensions.