Speaker
Description
We demonstrate how the shadow radius of regular black holes can serve as a powerful diagnostic tool for general relativity coupled with nonlinear electrodynamics (NED). By analyzing Bardeen-like, Hayward-like, and Maxwellian regular spacetimes, we highlight the critical distinction between standard null geodesics and the NED-driven effective photonsphere that governs light propagation. We show that the shadow radius carries distinct signatures of these field theories, acting as a sensitive probe for Lagrangian pathologies—evidenced by a unique discrepancy in the vanishing charge limit. Finally, using eikonal quasinormal modes, we confirm the robust correspondence between perturbations and the shadow size, proving it is strictly determined by the inverse angular velocity of the effective photonsphere.