Properties of the observed Ly alpha forest

The main observed properties of Ly alpha absorbers are investigated on the basis of a theoretical model of formation and evolution of dark matter (DM) structure elements. This model is generally consistent with simulations of absorber formation and with the statistical description of structure evolu tion based on the Zel'dovich theory. The analysis of redshift variations of comoving linear number density of absorbers was performed in our previous paper. We show that the observed characteristics of the Doppler parameter can be r elated to the size of DM structure elements that allow us to explain the ob served distribution of the Doppler parameter. This distribution is found to be consistent with the Gaussian initial perturbations. The observed charac teristics of entropy and column density N-Hi confirm that the merging of pa ncakes is the main evolutionary process at redshifts z greater than or equa l to2. The observed sample of absorbers mainly characterizes the matter dis tribution within large low-density regions and therefore it is difficult to reconstruct the density field from the distribution of absorbers.