Weak Gravitational Lensing by Large-Scale Structure

Abstract

Weak gravitational lensing provides a unique method to map directly the distribution of dark matter in the universe and to measure cosmological parameters. This cosmicshear technique is based on the measurement of the weak distortions that lensing induces in the shape of background galaxies as photons travel through large-scale structures. This technique is now widely used to measure the mass distribution of galaxy clusters and has recently been detected in random regions of the sky. In this review, we present the theory and observational status of cosmic shear. We describe the principles of weak lensing and the predictions for the shear statistics in favored cosmological models. Next, we review the current measurements of cosmic shear and show how they constrain cosmological parameters. We then describe the prospects offered by upcoming and future cosmic-shear surveys as well as the technical challenges that have to be met for the promises of cosmic shear to be fully realized.

Inflation and String Theory

“…With the exception of gravitational lensing [82][83][84], we do not measure the dark matter density δ directly. Instead, we observe biased baryonic tracers of the dark matter field, such as galaxies, clusters, and Lyα fluctuations: see the compilation of recent measurements in fig.…”

“…Corrections.-Because the setting (5.233) for poly-instanton inflation in [621] is precisely that of fibre inflation, while the geometry (5.234) in [783] is similar to that in blow-up inflation, one should ask about the string loop 83 The racetrack is unrelated to the existence of poly-instanton effects: it is a further model-building requirement. By introducing another adjustable parameter, the racetrack superpotential allows one to evade constraints that arise in a single-condensate model [621,783].…”

A Review on the Scalar Field/Bose-Einstein Condensate Dark Matter Model

“…The observed flatness of the galactic rotation curved indicating the presence of dark matter halos around galaxies [108]. Summed to these evidences are the observations of the cosmic microwave background (CMB) anisotropies ( [112,57]) combined with large-scale structure and type Ia supernova luminosity data ( [100,101,102,97]) which all together constrain the cosmological parameters also finding once more that visible matter contributes only about 4% of the energy density of the Universe, gravitational lensing [99] and X-ray spectra ( [69,37,116,36,87]) in elliptical galaxies, and the high velocity dispersion and gas temperature in clusters of galaxies ( [116,74]), all of them leading to a picture in which galaxies are composed of a luminous galactic disk surrounded by a galactic halo of dark matter. Also the relative contribution of the dark matter component is usually specified in terms of the mass-to-light ratio, M/L; which reflects the total amount of mass relative to the total light within a given scale.…”

Cosmological Parameters

“…Earlier results for comparison are summarized in Ref. 48. There are various systematic effects in the interpretation of weak lensing, e.g., due to atmospheric distortions during observations, the redshift distribution of the background galaxies, the intrinsic correlation of galaxy shapes, and non-linear modeling uncertainties.…”