Remarks on generalized scalar-tensor models of dark energy
  The generalized scalar-tensor models with Lagrangian
$F(\phi,R)-U(\phi)(\nabla\phi)^2$ are considered. It is shown that the
phantom-divide-line crossing and the deceleration to acceleration transition
generally occurr in these models. Two specific examples, the coupled
quintessence model and the Brans-Dicke model are considered. For the first
example, it is shown that for the models with $\xi>3/16$, the $\omega=-1$
transition exists. This is verified numerically for some special cases. For the
Brans-Dicke model, it is shown that the transition does not occur, a result
which can be verified by using the exact solution of this model. Finally the
contribution of quantum effects on these phenomena is investigated. It is shown
that for some special cases where the $\omega=-1$ transition is classically
forbidden, the quantum effects can induce transition. The $\xi=1/6$ of coupled
quintessence model is an example of this. The quantum effects are described via
the account of conformal anomaly.
