  Quintessential inflation is studied using a string modulus as the inflaton -
quintessence field. The modulus begins its evolution at the steep part of its
scalar potential, which is due to non-perturbative effects (e.g. gaugino
condensation). It is assumed that the modulus crosses an enhanced symmetry
point (ESP) in field space. Particle production at the ESP temporarily traps
the modulus resulting in a brief period of inflation. More inflation follows,
due to the flatness of the potential, since the ESP generates either an
extremum (maximum or minimum) or a flat inflection point in the scalar
potential. Eventually, the potential becomes steep again and inflation is
terminated. After reheating the modulus freezes due to cosmological friction at
a large value, such that its scalar potential is dominated by contributions due
to fluxes in the extra dimensions or other effects. The modulus remains frozen
until the present, when it can become quintessence and account for the dark
energy necessary to explain the observed accelerated expansion.
