Light-Cone Broadening and TeV Scale Extra Dimensions

TL;DR

This paper investigates how quantum-gravity effects in theories with large extra dimensions could cause observable light-cone broadening of photon signals, potentially detectable with current or near-future gravitational wave detectors.

Contribution

It analyzes light-cone broadening from both field- and string-theoretical perspectives, highlighting the role of D-brane recoil and astrophysical constraints on models with large extra dimensions.

Findings

Light-cone broadening may be within reach of current gravity-wave interferometers.

String-theoretical effects like D-brane recoil significantly influence light-cone broadening.

Astrophysical data impose strong limits on models with macroscopic extra dimensions.

Abstract

We examine the effect of light-cone broadening induced by quantum-gravity foam in the context of theories with ``large'' extra dimensions stretching between two parallel brane worlds. We consider the propagation of photon probes on one of the branes, including the response to graviton fluctuations, from both field- and string-theoretical viewpoints. In the latter approach, the dominant source of light-cone broadening may be the recoil of the D-brane, which scales linearly with the string coupling. Astrophysical constraints then place strong restrictions on consistent string models of macroscopic extra dimensions. The broadening we find in the field-theoretical picture seems to be close to the current sensitivity of gravity-wave interferometers, and therefore could perhaps be tested experimentally in the foreseeable future.