WEAK GRAVITATIONAL LENSING DUE TO LARGE-SCALE STRUCTURE OF THE UNIVERSE

We study the effect of the large-scale structure of the universe on the propagation of light rays. The development of the large-scale density fluctuations in the Ω = 1 universe is calculated within the cold dark matter scenario using a smooth particle approximation. The propagation of about 106 random light rays between the redshift z = 5 and the observer was followed. We find that the effect of shear is negligible, and the amplification of single images is dominated by the matter in the beam. The spread of amplifications is very small Therefore, the filled-beam approximation is very good for studies of strong lensing by galaxies or clusters of galaxies. In our simulation the column density was averaged over a comoving area of approximately (1h-1 Mpc)2. We found no case of a strong gravitational lensing, i.e., no "over-focused" image that would suggest that a few images might be present. Therefore, the large-scale structure of the universe as it is presently known does not produce multiple images with gravitational lensing on a scale larger than clusters of galaxies.