New constraints on quantum foam models from X-ray and gamma-ray observations of distant quasars

TL;DR

This paper uses X-ray and gamma-ray observations of distant quasars to test and constrain quantum gravity models predicting spacetime foam, ruling out several such models based on wavefront distortion effects.

Contribution

It explicitly connects wavefront distortions caused by quantum foam to observable image decay, providing new constraints on quantum gravity models from high-energy astrophysical data.

Findings

Ruling out certain spacetime foam models like random-walk and holographic.

Showing how wavefront distortions lead to the undetectability of distant sources.

Reassessing previous constraints with new observational data.

Abstract

Astronomical observations of distant quasars may be important to test models for quantum gravity, which posit Planck-scale spatial uncertainties ('spacetime foam') that would produce phase fluctuations in the wavefront of radiation emitted by a source, which may accumulate over large path lengths. We show explicitly how wavefront distortions cause the image intensity to decay to the point where distant objects become undetectable if the accumulated path-length fluctuations become comparable to the wavelength of the radiation. We also reassess previous efforts in this area. We use X-ray and gamma-ray observations to rule out several models of spacetime foam, including the interesting random-walk and holographic models.