Simulated evolution of the dark matter large-scale structure of the Universe

We analyse the evolution of the basic properties of the simulated elements of the large-scale structure of the Universe (LSS) formed by dark matter (DM), and we confront it with the observed evolution of the Lyman alpha forest. In three high-resolution simulations, we have selected samples of compact DM clouds of moderate overdensity. Clouds are selected at redshifts 0 <= z <= 3 with the minimal spanning tree technique. The main properties of the clouds selected in this way are analysed in three-dimensional space and with the core-sampling approach. This allows us to compare estimates of the DM LSS evolution obtained with two different techniques, and to clarify some important aspects of the LSS evolution. In both cases, we find that regular redshift variations of the mean characteristics of the DM LSS are accompanied only by small variations of their probability distribution functions (PDFs), which indicates the self-similar characteristic of the DM LSS evolution. A high degree of relaxation of DM particles, compressed within the LSS, is found along the shortest principal axis of the clouds. We see that the internal structure of the selected clouds depends upon the mass resolution and scale of the perturbations achieved in the simulations. It is found that the low-mass tail of the PDFs of the LSS characteristics depends upon the procedure of cloud selection.