  In many cases a massive nonlinear scalar field can lead to accelerated
expansion in cosmological models. This paper contains mathematical results on
this subject for flat Robertson-Walker space-time. Global existence to the
coupled Einstein-massive scalar field system which rules the dynamics of a kind
of pure matter in the presence of a massive scalar field and cosmological
constant is proved, under the assumption that the scalar field ? is a
non-decreasing function, in Robertson-Walker1 space-time; asymptotic behaviour
are investigated in the case of a cosmological constant bounded from below by a
strictly negative constant depending only on the massive scalar field.
