pretty thingUoP maths seminar (2015-16)



Strong gravitational lensing.

Speaker: Dr Thomas Collett (ICG, Portsmouth)

Venue: Wednesday 2nd December 2015, 2pm, LG2.04a (refreshments provided)

Abstract: In General Relativity mass warps space-time and light-rays follows geodesics. To an observer therefore, the paths of rays passing near to a massive object appear deflected. If the deflection is strong enough and a background source is sufficiently well aligned with the deflector multiple images of the source can form. This phenomenon is called strong gravitational lensing and has been observed in astronomical imaging. In this talk I will introduce the underlying mathematics of lensing, and present examples of how multiple imaging and extreme magnifications can occur with realistic galaxy mass profiles. I will then present recent work on the two screen compound-lens, where the deflections are caused by two galaxies at different distances from the observer. Finally I will show an example of a compound lens to measure distances in the Universe, and place constraints on the properties of the fluid that is causing the expansion of the Universe to accelerate ('Dark Energy').