Lightcone fluctuations in quantum gravity and extra dimensions

TL;DR

This paper explores how extra dimensions in quantum gravity can cause lightcone fluctuations, potentially observable through spectral line broadening from distant sources, with constraints on compactification scale derived from gamma ray burst data.

Contribution

It analyzes lightcone fluctuations in a five-dimensional model and establishes observational bounds on the size of extra dimensions.

Findings

Compactification length must be greater than about 10^5 cm.

Lightcone fluctuations can lead to observable spectral line broadening.

Data from gamma ray bursts constrain extra dimension size.

Abstract

We discuss how compactified extra dimensions may have potentially observable effects which grow as the compactification scale decreases. This arises because of lightcone fluctuations in the uncompactified dimensions which can result in the broadening of the spectral lines from distant sources. We analyze this effect in a five dimensional model, and argue that data from gamma ray burst sources require the compactification length to be greater than about $10^5$ cm in this model.