  In the light-front milieu, there is an implicit assumption that the vacuum is
trivial. By this " triviality " is meant that the Fock space of solutions for
equations of motion is sectorized in two, one of positive energy k- and the
other of negative one corresponding respectively to positive and negative
momentum k+. It is assumed that only one of the Fock space sector is enough to
give a complete description of the solutions, but in this work we consider an
example where we demonstrate that both sectors are necessary.
