Scale-Invariant Clustering and Primordial Biasing

If cosmic objects formed around the maxima of a scale-invariant (either Gaussian or non-Gaussian) density perturbation field, their correlation length and mean distance are proportional as suggested by the observations. Since the typical density contrast of a peak is v times greater than the field rms value, a size-independent, primordial threshold v is obtained whose magnitude depends only on the statistics; late nonlinear evolution would mainly affect the clustering properties of objects like galaxies. In this framework a simple, phenomenological model for the power-spectrum and a 'minimal,' isocurvature perturbation model are discussed.