PressSchechter
The Press–Schechter formalism, named after William H. Press and Paul Schechter, is a semi-analytic model in cosmology introduced in 1974 to predict the abundance of dark matter halos as a function of mass and cosmic time from the statistics of the initial density field.
The method starts from a Gaussian random field of initial density fluctuations and considers the fraction
The standard result can be written as n(M) dM = (ρ_m / M) f(ν) dν, where ν = δ_c / σ(M),
Applications include predicting halo abundances in simulations and analytic models, constructing merger trees, and informing galaxy