Speaker
Hendrik Hildebrandt
(Universität Bonn)
Description
Gravitational lensing represents a unique tool to study the dark
Universe. Small distortions in the images of galaxies caused by the
gravitational lensing effect of the matter distribution in the Universe
can be detected over the whole sky. Measuring these coherent distortions
makes dark matter structures "visible", allows us to study their growth
over cosmic time, and yields cosmological insights complementary to
other probes like the cosmic microwave background (CMB). Ongoing
wide-field imaging surveys exploit this weak gravitational lensing
technique to come up with competitive constraints on important
cosmological parameters and insights on fundamental physics.
In this talk I will first introduce the basic concepts of weak
gravitational lensing, review the history and challenges of weak lensing
measurements, and then concentrate on recent results from the ongoing
European Kilo Degree Survey (KiDS) and VISTA Kilo-degree Infrared Galaxy
Public Survey (VIKING) projects. These KiDS/VIKING measurements show
some tension with CMB measurements from the Planck mission when the
standard cosmological model is assumed. Does this tension represent a
first hint at a crack in our tremendously successful standard model of
cosmology? Or is our analysis of either of these measurements flawed in
some way? Possible solutions to this discrepancy using extensions to the
standard model of cosmology, like e.g. evolving forms of dark energy or
massive neutrinos, and possible future developments will be discussed. I
will conclude with an outlook towards the big experiments of the next
decade in this field of research, Euclid and the Large Synoptic Survey
Telescope that have the potential to yield some definitive answers to
these questions.
Primary author
Hendrik Hildebrandt
(Universität Bonn)
