Abstract
The aim of the present research is the analysis of the photon motion in the regular spacetimes arising as solutions of the Einstein gravity coupled with a non-linear electrodynamics (NED). The photons no longer follow the null geodesic of the background spacetime, but the null geodesics of an effective geometry where the electromagnetic non-linearity is directly reflected in addition to the spacetime geometry. Motion of photons is compared to the motion of neutrinos that are not directly affected by the non-linearities of a non-Maxwellian electromagnetic field, and follow null geodesics of the background spacetime. We determine shadows of the regular Bardeen black holes, representing a special solution of the general relativity coupled with NED related to a magnetic charge, both for photons and neutrinos, and compare them to the shadow of the related Reissner–Nordstrom black holes. We demonstrate that the direct NED effects give clear signature of the presence of the regular black holes, on the level going up to 20% that is detectable by recent observational techniques. We also demonstrate strong influence of the NED effects on deflection angle of photons moving in the Bardeen spacetimes, and on the time delay of the motion of photons and neutrinos in vicinity of the black hole horizon.
Highlights
In recent years, the Reissner–Nordstrom (RN) black holes are frequently studied in the astrophysical context
In the regular black hole backgrounds with charges related to a non-linear electrodynamics (NED), the motion of photons is not governed by the spacetime geometry, but by an effective geometry directly reflecting the non-linearities of the electrodynamics, as shown here in the Appendix
We have studied the simplest phenomena that could give a clear signature of the relevance of NED in the black hole spacetimes determined by the Einstein gravity
Summary
The Reissner–Nordstrom (RN) black holes are frequently studied in the astrophysical context. In its standard form governed by the Einstein–Maxwell theory with an electric charge as the source of the electromagnetic field, they are often applied as a model explaining the GRBs [38,40,56] – there is a criticism of the strong electric field paradigm [37] implying that existence of stable astrophysical black holes with a significant electric charge seems to be improbable. This argument is not relevant in the case of dyonic black holes carrying magnetic charge, as in the field of such black holes the vanishing of charge due to accretion of oppositely electrically charged matter is irrelevant. The RN black holes could be mimicked by the phantom fields [23], or by the Horndeski gravity [7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
