  We study the emission of large-scales wavelength space-time waves during the
inflationary expansion of the universe, produced by back-reaction effects. As
an example, we study an inflationary model with variable time scale, where the
scale factor of the universe grows as a power of time. The coarse-grained field
to describe space-time waves is defined by using the Levy distribution, on the
wavenumber space. The evolution for the norm of these waves on cosmological
scales is calculated, and it is shown that decreases with time.
