Constraints on the production of primordial magnetic seeds in pre-big
  bang cosmology
  We study the amplification of the electromagnetic fluctuations, and the
production of "seeds" for the cosmic magnetic fields, in a class of string
cosmology models whose scalar and tensor perturbations reproduce current
observations and satisfy known phenomenological constraints. We find that the
condition of efficient seeds production can be satisfied and compatible with
all constraints only in a restricted region of parameter space, but we show
that such a region has significant intersections with the portions of parameter
space where the produced background of relic gravitational waves is strong
enough to be detectable by aLIGO/Virgo and/or by eLISA.
