Lorentz-violating Euler-Heisenberg effective action
  In this work, we study the radiative generation of the Lorentz-violating Euler-Heisenberg action, in the weak field approximation. For this, we first consider a nonperturbative calculation in the coefficient $c_{\mu\nu}$, however, by assuming rotational invariance. Within this approach, we also obtain the results of the amplitude for the photon triple splitting. In the following, we take into account the perturbative approach, where $c_{\mu\nu}$ is treated as a insertion in the propagator and a new vertex. The partial results are in fact an expansion up to first order in $c_{\mu\nu}$ of the nonperturbative ones, with $c_{00}=\kappa$ and $c_{0i}=c_{ij}=0$. This suggest that the complete results obtained in the nonperturbative approach can be used in both treatments. 
J. Furtado, T. Mariz
hep-ph hep-th