  We revise the stability of the tracking solutions and briefly review the
potentials of quintessence models. We discuss the evolution of linear
perturbations for $V(\phi) = V_{0} \exp(\lambda \phi^2/2)$ potential in which
the scalar field is non-minimally coupled to cold dark matter. We consider the
effects of this coupling on both cosmic microwave background temperature
anisotropies and matter perturbations. We find that the phenomenology of this
model is consistent with current observations up to the coupling power $n_{c}
\leq 0.01$ while adopting the current parameters measured by WMAP,
$\Omega_{\phi}^{(0)}=0.76$, $\Omega_{cdm}^{(0)}=0.191$,
$\Omega_{b}^{(0)}=0.049$, and $h=0.70$. Upcoming cosmic microwave background
observations continuing to focus on resolving the higher peaks may put strong
constraints on the strength of the coupling.

Astrophysics