Phenomenological description of space-time foam

Abstract

The expectation that it should not be possible to gain experimental insight on the structure of space-time at Planckian distance scales has been recently challenged by several studies. With respect to space-time fluctuations, one of the conjectured features of quantum-gravity foam, the experiments that have the best sensitivity are the ones which were originally devised for searches of the classical-physics phenomenon of gravity waves. In experiments searching for classical gravity waves the presence of space-time fluctuations would introduce a source of noise just like the ordinary (non-gravitational) quantum properties of the photons composing the laser beam used in interferometry introduce a source of noise. Earlier studies of the noise induced by quantum properties of space-time have shown that certain simple pictures of fluctuations of space-time occuring genuinely at the Planck scale would lead to an observably large effect. Experimentalists would benefit from the guidance of detailed description of this noise, but quantum-gravity theories are not yet developed to the point of allowing such detailed analysis of physical processes. I propose a new phenomenological approach to the description of foam-induced noise.