QED effects on Kerr-Newman black hole shadows

By incorporating first-order QED effects, we explored the shadows of Kerr-Newman black holes with a magnetic charge through the numerical backward ray-tracing method. Our investigation encompassed both the direct influence of the electromagnetic field on light rays and the distortion of the background spacetime metric due to QED corrections. We found that the area of the shadow increases with the QED effect, mainly owing to the fact that the photons travel more slowly in the effective medium, making them more susceptible to being trapped by the black hole.