  Observational evidence shows that gravitational lensing induces an angular
correlation between the distribution of galaxies and much more distant QSOs. We
use weak gravitational lensing theory to calculate this angular correlation,
updating previous calculations and presenting new results exploring the
dependence of the correlation on the large-scale structure. We study the
dependence of the predictions on a variety of cosmological models, such as cold
dark matter models, mixed dark matter models, and models based on quintessence.
We also study the dependence on the assumptions made about the nature of the
primordial fluctuation spectrum: adiabatic, isocurvature and power spectra
motivated by the cosmic string scenario are investigated. Special attention is
paid to the issue of galaxy biasing, which is fully incorporated. We show that
different mass power spectra imply distinct predictions for the angular
correlation, and therefore the angular correlation provides an extra source of
information about cosmological parameters and mechanisms of structure
formation. We compare our results with observational data and discuss their
potential uses. In particular, it is suggested that the observational
determination of the galaxy-QSO correlation may be used to give an independent
measurement of the mass power spectrum.
