Distinguishing Dymnikova and Schwarzschild Black Holes through Gravitational Lensing with EFT-Corrected Photon Propagation

Abstract

We investigate whether a Dymnikova regular black hole can be observationally distinguished from a Schwarzschild black hole through strong gravitational lensing, taking into account effective field theory (EFT) corrections to photon propagation. We derive the modified photon propagation law induced by non-minimal couplings between the electromagnetic field and spacetime curvature and analyze the resulting photon trajectories in the Dymnikova spacetime. Within the strong deflection limit, we derive the EFT corrections to the photon sphere and the strong-deflection coefficients characterizing the logarithmically divergent behavior of the deflection angle. Although the EFT corrections are parametrically small, their effects can become relevant in the strong-deflection regime, where the deflection angle is highly sensitive to photon propagation near the critical orbit. We evaluate the strong-deflection observables for representative values of the Dymnikova parameter $\ell$ and compare them with the corresponding Schwarzschild results. We find that EFT corrections to photon propagation leave characteristic imprints on the strong-lensing observables. Furthermore, the contribution of the EFT corrections becomes more pronounced as the Dymnikova parameter $\ell$ approaches its critical value, indicating that the near-critical regime provides a particularly sensitive setting in which curvature-dependent corrections to photon propagation may affect gravitational lensing. These results suggest that strong gravitational lensing, together with EFT-induced modifications of photon propagation, may provide a means of distinguishing Dymnikova regular black holes from Schwarzschild black holes.