Press-Schechter formalism

The Press-Schechter formalism is a mathematical model yielding a density function of the masses of objects formed from initial fluctuations. The resulting function is analogous to the initial mass function (IMF), but rather than relative counts of stars, it yields the relative counts of large scale structures, i.e., dark matter halos, galaxy clusters, galaxies, etc. The model was published by William Press and Paul Schechter in 1974.