Dynamics of neutral and charged objects in gravitational fields coupled to nonlinear electrodynamics

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There are several reasons why to consider nonlinear electrodynamics: (i) it follows from quantum gravity scenarios based on string theory, (ii) it follows as effective theory from quantum electrodynamics (Heisenberg-Euler), (iii) it has been proposed in order to get rid of the infinities appearing in standard electrodynamics (Born-Infeld), and (iv) in the context of the Einstein field equations nonlinear electrodynamics models lead to regular black hole solutions. Though all experimental results are in accordance with standard quantum electrodynamics, the results from string theory and the particular features arising in the context of gravity theories make it worth to further investigate this class of theories, also towards new experimental tests in the laboratory (e.g. strong laser pulses) and in astrophysics (e.g. neutron stars, magnetars and gamma ray bursts). In this joint German-Mexican project we would like to investigate in a sytematic manner the propagation of light and of neutral and charged particles in space-times given within the framework of nonlinear electrodynamics. Due to the nonlinearity light does not propagate along null geodesics leading to particular effects for, e.g., shape dynamics, lensing, or the Faraday effect. The nonlinearity in general leads to birefringence and also should lead to effects like frequency doubling. We also want to take into acount the nonlinearity-induced backreaction for charged particles which may play a role in extreme situations. Furthermore, also extended particles with spin, magnetic moments, electric dipoles and higher-order charge multipoles will be considered. These results may be important for understanding the physics in the vicinity of neutron stars, magnetars, accretion discs, gamma ray bursts, etc., and also will be used to analyse or propose new experiments in strong electromagnetic fields like in strong laser pulses. In this context we also would like to find new solutions of the Einstein equations with nonlinear electrodynamics, in particular try to find rotating solutions extending the Kerr-Newman solution in the standard theory.