  The pole-like accelerated expansion stages purely driven by the coupling
between the gravity and the dilaton field without referring to the potential
term can be realized in a class of generalized gravity theories. We consider
three such scenarios based on the scalar-tensor gravity, the induced gravity
and the string theory. Quantum fluctuations during the expansion stages
(including more general situations) can be derived in exact analytic forms.
Assuming that the pole-like acceleration stage provides a viable inflation
scenario in the early universe we derive the generated classical density
spectrums. The generated classical density field shows a generic tilted
spectrum with $n \simeq 4$ which differs from the observed spectrum supporting
$n \simeq 1$.
