A variant of the Eden model with noise reduction is presented. A site is occupied if it is visited p times but the neighboring sites are added to the potential sites not after occupancy but immediately after the first visit. It results in aggregates with a very different pattern from that of...

We propose a simulation of the underground railway network of Paris which has an apparent fractal dimension equal to 1.8. We show that it is very likely that this value is due to a finite size effect and that the true dimension is 2. This means that caution is necessary in using the concept of...

We present an application of a growth model for a system of cities. This computer model simulates the evolution of systems with measurable entities (e.g. city size), and takes into account the growth of the entities in terms of size and number. It includes a random multiplicative process for...

We present a growth model for a system of cities. This model recovers not only Zipf's law but also other kinds of city size distributions (CSDs). A new positive exponent α, which yields Zipf's law only when equal to 1, was introduced. We define three classes of CSD depending on the value of α:...