CosmoSClub: 03-05-2018

Date: May 3rd 2018

Speaker: Alessio Spurio Mancini

Title: Weak gravitational lensing as a (3D) probe of gravity


Abstract

Cosmic shear, the weak gravitational lensing effect caused by the
large-scale structure, is one of the primary probes to test gravity on
cosmological scales with current and future surveys. In particular,
cosmic shear is sensitive to both standard GR cosmological parameters
and those that describe modified theories of gravity, such as those
belonging to the Horndeski class. These models include the majority of
universally coupled extensions to ΛCDM with one scalar degree of freedom
in addition to the metric, which are still in agreement with current
observations.
In this talk I will discuss some aspects concerning the constraining
power of current and future cosmic shear datasets on this broad class of
theories. I will compare in particular two main techniques to analyse a
cosmic shear survey: a tomographic method, where correlations between
the lensing signal in different redshift bins are used to recover
redshift information, and a 3D approach, where the full redshift
information is carried through the entire analysis. Due to its increased
amount of redshift information, a future 3D analysis can constrain both
standard gravity and Horndeski theories better than a tomographic one,
in particular with a decrease in the errors on the Horndeski parameters
of the order of 20%.