Search for quantum spacetime foam

The possibility that quantum fluctuations in the structure of spacetime at the Planck scale might be subject to experimental probes in discussed. The effects of spacetime foam in an approach inspired by string theory, in which solitonic D-brane excitations are taken into account when considering the ground state, are studied. The properties of this medium are described by analyzing the recoil of a D particle which is induced by the scattering of a closed-string state. This recoil causes an energy-dependent perturbation of the background metric, which in turn induces an energy-dependent refractive index in vacuo, and stochastic fluctuations of the light cone. Distant astrophysical sources such as Gamma-Ray Bursters (GRBs) may be used to test this possibility, and an illustrative analysis of GRBs whose redshifts have been measured is presented. The propagation of massive particles through such a quantum spacetime foam is also discussed.