The giant arc statistics in the three year WMAP cosmological model
  We use high-resolution $N$-body simulations to investigate the optical depth of giant arcs with length-to-width ratio larger than 7.5 and 10 in the `standard' $\LCDM$ model with $\sigma_8=0.9$ and $\Omega_{\rm m,0}=0.3$ and a model based on three-year Wilkinson Microwave Anisotropy Probe (WMAP) data. We find that, in dark-matter only simulations, the lensing probability in the three-year WMAP model (with $\sigma_8=0.74$ and $\Omega_{\rm m,0}=0.238)$ decreases by a factor of $\sim 6$ compared with that in the `standard' $\LCDM$ model. The effects of baryonic cooling, star formation and feedbacks are uncertain, but we argue that baryons will only increase the the lensing cross-section by a moderate factor, $\sim 2$. We conclude that the low central value of $\sigma_8$ and $\Omega_{\rm m,0}$ preferred by the WMAP three-year data may be too low to be compatible with observations if conventional assumptions of the background source population are correct. 
G. L. Li, S. Mao, Y.P. Jing, H.J. Mo, L. Gao, W.P. Lin