Gravitational-Recoil Effects on Fermion Propagation in Space-Time Foam

TL;DR

This paper explores how quantum gravity effects, modeled via D-brane recoil in space-time foam, could cause high-energy fermions like neutrinos to travel slower than light, with potential observable consequences in astrophysical phenomena.

Contribution

It introduces a supersymmetric D-brane framework to incorporate spin effects in gravitational recoil, predicting energy-dependent fermion velocity reductions.

Findings

High-energy neutrinos may travel slower than light by c c d  E/M.

Observable effects require a quantum gravity scale M  10^{27} GeV.

Analogies with condensed matter systems provide additional insights.

Abstract

Motivated by the possible experimental opportunities to test quantum gravity via its effects on high-energy neutrinos propagating through space-time foam, we discuss how to incorporate spin structures in our D-brane description of gravitational recoil effects in vacuo. We also point to an interesting analogous condensed-matter system. We use a suitable supersymmetrization of the Born-Infeld action for excited D-brane gravitational backgrounds to argue that energetic fermions may travel slower than the low-energy velocity of light: \delta c / c \sim -E/M. It has been suggested that Gamma-Ray Bursters may emit pulses of neutrinos at energies approaching 10^{19} eV: these would be observable only if M \gsim 10^{27} GeV.