  We study the possibility that the Dilaton is stabilized by the contribution
of fermion masses to its effective potential. We consider the Dilaton gravity
action in four dimensions to which we add a mass term for a Dirac fermion. Such
an action describes the interaction of the Dilaton with the fermions in the
Yang-Mills sector of the coupled supergravity/super-Yang-Mills action which
emerges as the low energy effective action of superstring theory after the
extra spatial dimensions have been fixed. The Dilaton couples to the Fermion
mass term via the usual exponential factor of this field which multiplies the
non-kinetic terms of the matter Lagrangian, if we work in the Einstein frame.
In the kinetic part of the Fermion action in the Einstein frame the Dilaton
does not enter. Such masses can be generated in several ways: they can arise as
a consequence of flux about internal spatial dimensions, they may arise as
thermal fermion masses in a quasi-static phase in the early universe, and they
will arise after the breaking of supersymmetry at late times. The vacuum
contribution to the potential for the Dilaton is evaluated up to two loops. The
result shows a minimum which could stabilize the Dilaton for reasonable ranges
of parameter values.
