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“Four Applications of Gravitational Lensing” Dr. Saul Rappaport MIT |
| The first part of the talk will briefly review some of the basics of gravitational lensing. The second part will discuss four current applications of strong lensing. (1) Analysis of flux ratio anomalies in 4-image lenses of quasars by elliptical galaxies provides information on a micro-arcsecond scale about quasar accretion disks as well as the dark-matter content in the lensing galaxy. (2) A collection of elliptical galaxies lensing emission-line galaxies has allowed us to set a constraint on the post-Newtonian parameter gamma in the Schwarzschild metric - on kpc scales. (3) The same collection of galaxy-galaxy lenses, in principle, can lead to an independent determination of Omega_Lambda; in practice there are a number of systematic effects that make this a difficult problem. (4) The giant arcs in clusters of galaxies allow for a probe of the clumpiness of the dark-matter structure in these massive objects. |