Tests of Loop Quantum Gravity from the Event Horizon Telescope Results of Sgr A

The Event Horizon Telescope (EHT) collaboration's image of the compact object at the Galactic center is the first direct evidence of the supermassive black hole (BH) Sgr A*. The shadow of Sgr A* has an angular diameter d(sh) = 48.7 +/- 7 mu as with fractional deviation from the Schwarzschild BH shadow diameter delta = -0.08(-0.09)(+0.09),-0.04(-0.10)(+0.09) (for the VLTI and Keck mass-to-distance ratios). Sgr A*'s shadow size is within 10% of Kerr predictions, equipping us with yet another tool to analyze gravity in the strong-field regime, including testing loop quantum gravity (LQG). We use Sgr A*'s shadow to constrain the metrics of two well-motivated LQG-inspired rotating BH (LIRBH) models characterized by an additional deviation parameter L-q , which recover the Kerr spacetime in the absence of quantum effects (L-q -> 0). When increasing the quantum effects through L-q, the shadow size increases monotonically, while the shape gets more distorted, allowing us to constrain the fundamental parameter L-q. We use the astrophysical observables shadow area A and oblateness D to estimate the BH parameters. It may be useful in extracting additional information about LIRBHs. While the EHT observational results completely rule out the wormhole region in LIRBH-2, a substantial parameter region of the generic BHs in both models agrees with the EHT results. We find that the upper bounds on L-q obtained from the shadow of Sgr A*-L-q less than or similar to 0.0423 and L-q less than or similar to 0.0821 for the two LIRBHs, respectively-are more stringent than those obtained from the EHT image of M87*.