  In the very early Universe matter can be described as a conformal invariant
ultra-relativistic perfect fluid, which does not contribute, on classical
level, to the evolution of the isotropic and homogeneous metric. However, in
this situation the vacuum effects of quantum matter fields become important.
The vacuum effective action depends, essentially, on the particle content of
the underlying gauge model. If we suppose that there is some desert in the
particle spectrum, just below the Planck mass, then the effect of conformal
trace anomaly is dominating at the corresponding energies. With some additional
constraints on the gauge model (which favor extended or supersymmetric versions
of the Standard Model rather than the minimal one), one arrives at the stable
inflation. In this article we report about the calculation of the gravitational
waves in this model. The result for the perturbation spectrum is close to the
one for the conventional inflaton model, and is in agreement with the existing
Cobe data.
