Galaxy-QSO correlation induced by weak gravitational lensing arising from large-scale structure

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 correl ation, updating previous calculations and presenting new results exploring the dependence of the correlation on the large-scale structure. We study th e dependence of the predictions on a variety of cosmological models, such a s cold dark matter models, mixed dark matter models and models based on qui ntessence. We also study the dependence on the assumptions made about the n ature of the primordial fluctuation spectrum: adiabatic, isocurvature and p ower spectra motivated by the cosmic string scenario are investigated. Spec ial attention is paid to the issue of galaxy biasing, which is fully incorp orated. We show that different mass power spectra imply distinct prediction s for the angular correlation, and therefore the angular correlation provid es an extra source of information about cosmological parameters and mechani sms of structure formation. We compare our results with observational data and discuss their potential uses. In particular, it is suggested that the o bservational determination of the galaxy-QSO correlation may be used to giv e an independent measurement of the mass power spectrum.