Planck-Scale Gravity Test at PETRA

Abstract

Quantum or torsion gravity models predict unusual properties of spacetime at very short distances. In particular, near the Planck length, around 10$^{−35}$ m, empty space may behave as a crystal, singly or doubly refractive. This hypothesis, however, remains uncheckable for any direct measurement since the smallest distance accessible in experiment is about 10$^{−19}$ m at the LHC. Here we propose a laboratory test to measure space birefringence or refractivity induced by gravity. A sensitivity 10$^{−31}$ m for doubly and 10$^{−28}$ m for singly refractive vacuum could be reached with PETRA 6 GeV beam exploring UV laser Compton scattering