  Using tachyon or quintessence fields along with a barotropic fluid on the
brane we examine the different cosmological stages in a
Friedmann-Robertson-Walker(FRW) universe, from the first radiation scenario to
the later era dominated by cosmic string networks. We introduce a new algorithm
to generalize previous works on exact solutions and apply it to study tachyon
and quintessence fields localized on the brane and study the low and high
energy regimes. We show that the tachyon and quintessence fields are driven by
an inverse power law potential. Finally, we find several simples exacts
solutions for tachyon and/or quintessence fields.
