Quantum Gravity Effects around Sagittarius A*
  Recent VLBI observations have resolved Sagittarius A* at horizon scales. The Event Horizon Telescope is expected to provide increasingly good images of the region around the Schwarzschild radius $r_S$ of Sgr A* soon. A number of authors have recently pointed out the possibility that non-perturbative quantum gravitational phenomena could affect the space surrounding a black hole. Here we point out that the existence of a region around $\frac76 r_S$ where these effects should be maximal. 
Hal M. Haggard and Carlo Rovelli
gr-qc