 Such functions had previously been noted by Schechter
as observed luminosity functions,
and are now known as Schechter luminosity functions.The Press-Schechter
formalism provided the first quantitative model for how such functions might
arise.The case of a scale-free power spectrum, "n"=0 (or, equivalentlty, a scalar spectral index of 1), is very close to the spectrum of the current standard cosmological model.