Gravitational lenses in the dark Universe
  We discuss how different cosmological models of the Universe affect the
probability that a background source has multiple images related by an angular
distance $\theta_E$ of the line of sight, \textit{i. e.}, the optical depth of
gravitational lensing. We examine some cosmological models for different values
of the density parameter $\Omega_i$: i) the cold dark matter model, ii) the
$\Lambda$CDM model, iii) the Bose-Einstein condensate dark matter model, iv)
the Chaplygin gas model, v) the viscous fluid cosmological model and vi) the
holographic dark energy model. We note that the dependence of the energy-matter
content of the universe profoundly alters the frequency of multiple quasar
image.
