MODELING THE CLUSTERING OF BOUND OBJECTS

We discuss the foundations of a new formalism presented elsewhere for the construction of a detailed model of hierarchical clustering via gr avitational instability from an initial random Gaussian field of densi ty fluctuations. Similarly to other formalisms the new one also deals with clustering through the filtering process of the density field at an arbitrary fixed early epoch. Its interest relies on the fact that i t is fully justified and, as an extra bonus, it makes the important pr actical distinction between accretion and mergers. In the present pape r we try to clarify why such a simple approach is able to provide a co rrect statistical description of the growth history of objects.