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Geometrical Effects Associated to Non-Linear Eletrodynamics

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In a recent communication (M.Novello, V.A.De Lorenci, J.M.Salim e R.Klippert,
Physical Review D 61, 045001, 2000), it is shown that
non-linear processes of Electromagnetism do 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", according to the
background electromagnetic field. It shall 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 provide for 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 in 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 laboratorial black hole 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, but rather 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).