Testing A (Stringy) Model of Quantum Gravity

TL;DR

This paper explores a string-inspired quantum gravity model involving D-branes and D-particles, predicting observable effects like modified dispersion relations and refractive indices, which can be tested with astrophysical and laboratory experiments.

Contribution

It introduces a specific stringy space-time foam model with testable predictions, linking quantum gravity effects to observable phenomena.

Findings

Modified dispersion relations for particles.

Potential observable effects in astrophysical signals.

Testable predictions for future experiments.

Abstract

I discuss a specific model of space-time foam, inspired by the modern non-perturbative approach to string theory (D-branes). The model views our world as a three brane, intersecting with D-particles that represent stringy quantum gravity effects, which can be real or virtual. In this picture, matter is represented generically by (closed or open) strings on the D3 brane propagating in such a background. Scattering of the (matter) strings off the D-particles causes recoil of the latter, which in turn results in a distortion of the surrounding space-time fluid and the formation of (microscopic, i.e. Planckian size) horizons around the defects. As a mean-field result, the dispersion relation of the various particle excitations is modified, leading to non-trivial optical properties of the space time, for instance a non-trivial refractive index for the case of photons or other massless probes. Such models make falsifiable predictions, that may be tested experimentally in the foreseeable future. I describe a few such tests, ranging from observations of light from distant gamma-ray-bursters and ultra high energy cosmic rays, to tests using gravity-wave interferometric devices and terrestrial particle physics experients involving, for instance, neutral kaons.