Weak gravitational lensing

We review theory and applications of weak gravitational lensing. After summarising Friedmann–Lemaı̂tre cosmological models, we present the formalism of gravitational lensing and light propagation in arbitrary space–times. We discuss how weak-lensing effects can be measured. The formalism is then applied to reconstructions of galaxy-cluster mass distributions, gravitational lensing by large-scale matter distributions, QSO–galaxy correlations induced by weak lensing, lensing of galaxies by galaxies, and weak lensing of the cosmic microwave background.