Scale-invariant scalar metric fluctuations during inflation: non-perturbative formalism from a 5D vacuumM. Anabitarte, M. Bellini and José Edgar Madriz AguilarEur. Phys. J. C, 65 1-2 (2010) 295-301DOI: https://doi.org/10.1140/epjc/s10052-009-1180-2