The substructure in clusters of galaxies are expected to be indicators of Universal parameters. Following my thesis work I showed that tracers of mass like gravitation lensing are better estimators of substructure than galaxies. This was work done with Dr. M. Bartelmann at the Max-Plank institute. We computed the properties of arcs formed from ~ 30,000 sources by the gravitational lensing effect of the simulated clusters and summarise the results by giving cross sections for the formation of arcs with a variety of properties. The most important of our results is that the formation of large arcs is strongly suppressed in an open universe. The cross section for arcs with a length-to-width ratio greater than 5 is smaller by more than an order of magnitude in the open compared to the flat model universe, and arcs with length-to-width ratios greater than 8 virtually do not appear in the open universe.
The temperature fluctuations of the microwave background radiation remains one of the most important constraints on the theories of Large Scale Structure formation. New observations of the fluctuations on the degree scales are particularly important because it is near the scales which the other measures of large scale structure probe. It is therefore important to model the expected observations of the temperature fluctuations in different scenarios for different experimental setups. It is possible to place fairly strong limits on models like the primeval isocurvature baryon model from current observations.
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