Thirty years ago, in a seminal letter published by Nature, Alcock & Paczynski (AP) proposed a strategy to solve one of the most outstanding issues of cosmology: measuring the curvature of the universe with a model independent, purely geometrical, approach. Despite its power and elegance, this idea has never been substantiated.

Previous attempts to detect the AP effect failed because the peculiar, non-Hubble, motions of cosmic objects induce AP-like distortions which are difficult to model and subtract.
I will discuss how this issue can be successfully addressed by studying the symmetry properties of distant pairs of galaxies. Specifically, I will show that the pairs orientation is a new and promising observable which can be used to probe the value of fundamental cosmological parameters. I will present the constraints obtained by implementing this method to archival data from the SDSS and DEEP2 redshift surveys and speculate on the precision achievable with data from future redshift surveys. I will conclude by showing how the formalisms can be applied, on larger cosmological scales, to assess the coherence of the Copernican Principle.

ADRESSE:
LPNHE
4 place Jussieu PARIS 5eme
Barre 12-22
RC
Room 8
lLink: http://www.nature.com/news/2010/101124/full/news.2010.629.html