Einstein's gravitational lensing and nonlinear electrodynamics

In 1936 Einstein predicted the phenomenon presently known as gravitational lensing (GL). A prime feature of GL is the magnification, because of the gravitational field, of the star visible surface as seen from a distant observer. We show here that nonlinear electrodynamics (NLED) modifies in a fundamental basis Einstein's general relativistic (GR) original derivation. The effect becomes apparent by studying the light propagation from a strongly magnetic ($B$) pulsar (SMP). Unlike its GR counterpart, the photon dynamics in NLED leads to a new effective GL, which depends also on the $B$-field permeating the pulsar. The apparent radius of a SMP appears then unexpectedly diminished, by a large factor, as compared to the classical Einstein's prediction. This may prove very crucial in determining physical properties of high $B$-field stars from their X-ray emission.