CONFRONTING COLD DARK-MATTER COSMOLOGIES WITH STRONG CLUSTERING OF LYMAN BREAK GALAXIES AT Z-SIMILAR-TO-3

We perform a detailed analysis of the statistical significance of a co ncentration of Lyman break galaxies at z similar to 3 recently discove red by Steidel et al., using a series of N-body simulations with N = 2 56(3) particles in a (100 (h-1) Mpc)(3) comoving box. While the observ ed number density of Lyman break galaxies at z similar to 3 implies th at they correspond to systems with dark matter halos of less than or s imilar to 10(12) M-., the resulting clustering of such objects on aver age is not strong enough to be reconciled with the concentration if it is fairly common; we predict one similar concentration approximately per 6-10 fields in three representative cold dark matter models. Consi dering the current observational uncertainty of the frequency of such clustering at z similar to 3, it would be premature to rule out the mo dels, but the future spectroscopic surveys in a dozen fields could def initely challenge all the existing cosmological models a posteriori fi tted to the z = 0 universe.