Generalized tracker quintessence models for dark energy
  We study the dynamical properties of tracker quintessence models using a
general parametrization of their corresponding potentials, and show that there
is a general condition for the appearance of a tracker behavior at early times.
Likewise, we determine the conditions under which the quintessence tracker
models can also provide an accelerating expansion of the universe with an
equation of state closer to $-1$. Apart from the analysis of the background
dynamics, we also include linear density perturbations of the quintessence
field in a consistent manner and using the same parametrization of the
potential, with which we show the influence they have on some cosmological
observables. The generalized tracker models are compared to observations, and
we discuss their appropriateness to ameliorate the fine-tuning of initial
conditions and their consistency with the accelerated expansion of the Universe
at late times.
