Measuring Omega_m using clusters evolution
  The constraints obtained by several authors (Eke et al. 1998; Henry 2000) on the estimated values of $\Omega_{\rm m}$, $n$ and $\sigma_8$ are revisited in the light of recent theoretical developments: 1) new theoretical mass functions; 2) a more accurate mass-temperature relation, also determined for arbitrary $\Omega_{\rm m}$ and $\Omega_{\rm \Lambda}$. I re-derive the X-ray Temperature Function (XTF), similarly to Henry (2000) and Eke et al. (1999), re-obtaining the constraints on $\Omega_{\rm m}$, $n$, $\sigma_8$. The result shows that changes in the mass function and M-T relation produces an increase in $\Omega_{\rm m}$ of $ \simeq 20%$ and similar results in $\sigma_8$ and $n$. 
A. Del Popolo (Bergamo University, Italy)