Nonlinear magnetic response of the magnetized vacuum to applied electric   field
  We find first nonlinear correction to the field, produced by a static charge at rest in a background constant magnetic field. It is quadratic in the charge and purely magnetic. The third-rank polarization tensor - the nonlinear response function - is written within the local approximation of the effective action in an otherwise model- and approximation-independent way within any P-invariant nonlinear electrodynamics, QED included. 
Dmitry M. Gitman (1) and Anatoly E. Shabad (2) ((1) Instituto de   F\'isica, Universidade de S\~ao Paulo, S.P., Brazil (2) P...
hep-th astro-ph.HE physics.atom-ph