In a recent communication (M.Novello, V.A.De Lorenci, J.M.Salim e R.Klippert, Physical Review D 61, 045001, 2000), it was shown that non-linear processes of Electromagnetism have a remarkable property: field discontinuites in a non-linear theory propagate as if the space-time geometry had changed, from a Minkowski type to a kind of ?effective geometry?, that depends on the background electromagnetic field. It should be pointed out here that such ?new? geometry has no relation to any gravitational process: it is a pure electromagnetic feature. The similarity of photon behavior in such non-linear processes with gravity suggests the existence of electromagnetic systems resembling gravitational ones. Some interesting results have already been obtained. For instance, the possibility of generating an effective geometry exhibiting photon confinement. Such system could be called an electromagnetic black hole. It was also possible to obtain an effective geometry endowed with the features of a gravitational wormhole for photons (F.Baldovin, M.Novello, S.E.P.Bergliaffa e J.Salim, 2000). Along these lines, other analogs of gravitational systems are presently under study.

The fact that vacuum non-linear electromagnetic theories can be interpreted as non-linear theories in the presence of a medium suggests that the systems mentioned above could be produced in the laboratory, by means of appropriate material media. In particular, the generation of a black hole of this type in the laboratory is currently under analysis.

It should be streesed that the effective geometry approach is still valid in the case of a curved background induced by a non-linear electromagnetic field. Once again, it is found that photons do not travel along geodesics of the background metric; instead they follow geodesics of an effective metric. Making use of the effective geometry associated to a so-called non-singular black hole, it can be shown that the black hole has singularities experienced as such only by photons (M.Novello, S.E.P.Bergliaffa e J.M.Salim, 2000).