  Gravitational stability of torsion and inflaton field in a four-dimensional
spacetime de Sitter solution in scalar-tensor cosmology where Cartan torsion
propagates is investigated in detail. Inflaton and torsion evolution equations
are derived by making use of a Lagrangean method. Stable and unstable modes for
torsion and inflatons are found to be dependent of the background torsion and
inflaton fields. Present astrophysical observations favour a stable mode for
torsion since this would explain why no relic torsion imprint has been found on
the Cosmic Background Radiation in the universe.
