  The existence of a dark energy component has usually been invoked as the most
plausible way to explain the recent observational results. However, it is also
well known that effects arising from new physics (e.g., extra dimensions) can
mimic the gravitational effects of a dark energy through a modification of the
Friedmann equation. In this paper we investigate some observational
consequences of a flat, matter dominated and accelerating/decelerating scenario
in which this modification is given by $H^{2} = g(\rho_m, n, q)$ where
$g(\rho_m, n, q)$ is a new function of the energy density $\rho_m$, the
so-called generalized Cardassian models. We mainly focus our attention on the
constraints from statistical properties of gravitationally lensed quasars on
the parameters $n$ and $q$ that fully characterize the models. We show that
these models are in agreement with the current gravitationally lensed quasar
data for a large interval of the $q - n$ parametric space. The dependence of
the acceleration redshift (the redshift at which the universe begins to
accelerate) on these parameters is also briefly discussed.

Astrophysics