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# FrontPage

last edited by 15 years, 8 months ago

# OVERVIEW

This Website has been compiled as all purpose tool for Gravitational Lensing. It is designed for both newbies who would like to learn about more about lensing as well as professionals who wish to share resources. For the purposes of this site we shall be using the following definitions for different lensing regimes:

• Strong Lensing: Strong lensing is when the effects of gravitational lensing are so high that a single source produces multiple images. This usually occurs if the light from a distant object passes very close to the centre of a galaxy or cluster. In this scenario the positions, magnifications and time delay of the images is used to study the lens, source of background cosmology.

• Weak Lensing: Weak lensing occurs when the gravitational lensing effect is not strong enough to cause multiple images. Instead the image of a distant object is distorted by foreground objects. By measuring the distortion pattern of background objects, we are able to measure and reconstruct the mass of foreground objects.

• Cosmic Lensing: Even if we look at patches of sky that is fairly ‘empty’ the light from distant objects will be perturbed by the general matter distribution of the Universe. In this regime lensing is studied using statistical techniques, such as the two point correlation function of the shape distortions. These statistics are used to measure general properties of the Universe such as the amount and type of dark matter and dark energy.

• Micro Lensing: Micro lensing is typically used to the lensing of point like objects, for instance stars are small and distant that they behave like a point source. Here we track the brightness of these objects since the lensing by an object that moves between us and the background star (this is typically another star, a black hole or a lump of dark matter) causes the temporary brightening of the background star. One application of micro lensing is the search or Earth-like extra solar planets.