Quantum effects on the deflection of light and the Gauss-Bonnet theorem

In this paper, we apply the Gauss-Bonnet (GB) theorem to calculate the deflection angle by a quantum-corrected Schwarzschild black hole in the weak limit approximation. In particular, we calculate the light deflection by two types of quantum-corrected black holes: the renormalization group improved Schwarzschild solution and the quantum-corrected Schwarzschild solution in Bohmian quantum mechanics. We start from the corresponding optical metrics to use then the GB theorem and calculate the Gaussian curvature in both cases. We calculate the leading terms of the deflection angle and show that quantum corrections modify the deflection angle in both solutions. Finally by performing geodesics calculations we show that GB method gives exact results in leading-order terms.