From the averaging problem to lensing

From Lecospa
Jump to: navigation, search

We live in an inhomogeneous Universe, but we often treat it as homogeneous. We also know that GR is non-linear, and that can be potentially the source of troubles. We call that the averaging problem of cosmology and it has led to many disputes in the past. I will take a mitigate position and show what my thesis said about this problem, showing a possible percent effect on dark energy. Rather than focusing on the debate of whether or not we could explain dark energy with averaging, I will present some tools and especially a system of coordinates which is very useful when we deal with light propagated observables, i.e. almost all of them. One recent application I made from it is to compute weak lensing quantities, and we find very elegant expressions. If I have time I will also tell you about my other big interest which is strong lensing, as a teaser for a possible other seminar. Stay tuned!