  The $\alp-\alp$ interaction potential is obtained within the double folding
model with density-dependent Gogny effective interactions as input. The one
nucleon knock-on exchange kernel including recoil effects is localized using
the Perey-Saxon prescription at zero energy. The Pauli forbidden states are
removed thanks to successive supersymmetric transformations. Low energy
experimental phase shifts, calculated from the variable phase approach, as well
as the energy and width of the first $0^+$ resonance in $^8$Be are reproduced
with high accuracy.
