The clustering of X-ray selected AGN appears to be a valuable tool for extracting cosmological information .
Using the recent high-precision angular clustering results of \sim 30000 XMM- Newton soft ( 0.5-2 keV ) X-ray sources ( Ebrero et al .
) , which have a median redshift of z \sim 1 , and assuming a flat geometry , a constant in comoving coordinates AGN clustering evolution and the AGN bias evolution model of Basilakos et al. , we manage to break the \Omega _ { m } - \sigma _ { 8 } degeneracy .
The resulting cosmological constraints are : \Omega _ { m } = 0.27 ^ { +0.03 } _ { -0.05 } , w = -0.90 ^ { +0.10 } _ { -0.16 } and \sigma _ { 8 } = 0.74 ^ { +0.14 } _ { -0.12 } , while the dark matter host halo mass , in which the X-ray selected AGN are presumed to reside , is M = 2.50 ^ { +0.50 } _ { -1.50 } \times 10 ^ { 13 } h ^ { -1 } M _ { \odot } .
For the constant \Lambda model ( w= -1 ) we find \Omega _ { m } = 0.24 \pm 0.06 and \sigma _ { 8 } = 0.83 ^ { +0.11 } _ { -0.16 } , in good agreement with recent studies based on cluster abundances , weak lensing and the CMB , but in disagreement with the recent bulk flow analysis .

Keywords : cosmology : cosmological parameters , large scale structure of the universe