Evolution of bias in different cosmological models
  We study the evolution of the halo-halo correlation function and bias in four cosmological models (LCDM, OCDM, tauCDM, and SCDM) using very high-resolution N-body simulations. The high force and mass resolution allows dark matter (DM) halos to survive in the tidal fields of high-density regions and thus prevents the ambiguities related with the ``overmerging problem.'' This allows us to estimate for the first time the evolution of the correlation function and bias at small (down to ~100/h kpc) scales. We find that at all epochs the 2-point correlation function of galaxy-size halos xi_hh is well approximated by a power-law with slope ~1.6-1.8. The difference between the shape of xi_hh and the shape of the correlation function of matter results in the scale-dependent bias at scales <7/h Mpc, which we find to be a generic prediction of the hierarchical models. The bias evolves rapidly from a high value of ~2-5 at z~3-7 to the anti-bias of b~0.5-1 at small <5/h Mpc scales at z=0. We find that our results agree well with existing clustering data at different redshifts. Particularly, we find an excellent agreement in both slope and the amplitude between xi_hh(z=0) in our LCDM simulation and the galaxy correlation function measured using the APM galaxy survey. At high redshifts, the observed clustering of the Lyman-break galaxies is also well reproduced by the models. The agreement with the data at high and low z indicates the general success of the hierarchical models of structure formation in which galaxies form inside the host DM halos. (Abridged) 
Pedro Colin (UNAM), Anatoly Klypin (NMSU), Andrey Kravtsov (NMSU),   Alexei Khokhlov (NRL)