STATISTICAL TESTS FOR CHDM AND LAMBDA-CDM COSMOLOGIES

We apply several statistical estimators to high-resolution N-body simu lations of two currently viable cosmological models: a mixed dark matt er model, having Omega(nu) = 0.2 contributed by two massive neutrinos (C + 2 nu DM), and a cold dark matter model with cosmological constant (Lambda CDM) with Omega(0) = 0.3 and h = 0.7. Our aim is to compare s imulated galaxy samples with the Perseus-Pisces redshift survey (PPS). We consider the n-point correlation functions (n = 2-4); the N-count probability functions P-N, including the void probability function P-0 ; and the underdensity probability function U-epsilon (where epsilon f ixes the underdensity threshold in percentage of the average). We find that P-0 (for which PPS and CfA2 data agree) and P-1 distinguish effi ciently between the models, while U-epsilon is only marginally discrim inatory. On the contrary, the reduced skewness and kurtosis are, respe ctively, S-3 similar or equal to 2.2 and S-4 similar or equal to 6-7 i n all cases, quite independent of the scale, in agreement with hierarc hical scaling predictions and estimates based on redshift surveys. Amo ng our results, we emphasize the remarkable agreement between PPS data and C + 2 nu DM in all the tests performed. In contrast, the above La mbda CDM model has serious difficulties in reproducing observational d ata if galaxies and matter overdensities are related in a simple way.