Introduction to Gravitational Lensing and Cosmology

Abstract

In this introductory first part we shall provide an outline of the basics of gravitational lensing, covering aspects that are at the base of it and which will be used extensively in the three main lectures. We start with a brief historical account; the study of the influence of a gravitational field on the propagation of light started long before the proper theory of gravity - Einstein's General Relativity - was formulated. Illustrations of the most common phenomena of gravitational lensing will be given next, before we will introduce the basic equations of gravitational lensing theory. A few simple lens models will be considered in particular the point-mass lens and the singular isothermal sphere model. Since the sources and deflectors in gravitational lensing are often located at distances comparable to the radius of the observable Universe, the large-scale geometry of spacetime needs to be accounted for. Thus, we give a brief introduction to the standard model of cosmology. We then proceed with some basic considerations about lensing statistics, i.e., the question of how probable it is that observations of a source at large distance are significantly affected by a lensing effect, and conclude with a description of the large-scale matter distribution in the Universe.