The evolution of core collections can be described via Banach space valued stochastic processes

Core collections, as e.g., the set of source journals selected by the Institute for Scientific Information, vary from year to year: most of them stay, some leave, and others enter. s paper, we show that the mechanism of this process can be revealed by using stochastic processes with values in an infinite dimensional Banach space. More concretely we show that the evolution can be described by a quasi-martingale with values in the Hubert space L2. Criteria for the convergence of these processes are given, leading to a stable limit set of core items, for t (time) high.