Random graph theory is used to model relationships between sequences and secondary structure of RNA molecules. Sequences folding into identical structures form neutral networks which percolate sequence space if the fraction of neutral nearest neighbors exceeds a threshold value. The networks of...

A new model ecosystem consisting of many interacting species is introduced. The species are connected through a random matrix with a given connectivity . It is shown that the system is organized close to a boundary of marginal stability in such a way that fluctuations follow power law...

We analyze the structure of a large metabolic network, that of the energy and biosynthesis metabolism of Escherichia coli. This network is a paradigmatic case for the large genetic and metabolic networks that functional genomics efforts are beginning to elucidate. To analyze the structure of...

In this paper, we construct a computational model of Tiebout competition. We show that the notion that Tiebout competition, as a result of enforcing efficiency, renders institutional arrangements unimportant does not preclude the possibility that political institutions may differ in their...

Many complex systems can be described in terms of networks of interacting units. Recent studies have shown that a wide class of both natural and artificial nets display a surprisingly widespread feature: the presence of highly heterogeneous distributions of links, providing an extraordinary...

We illustrate and extend the techniques of computational mechanics in explicating the structures that emerge in the space-time behavior of elementary one-dimensional cellular automaton rule 54. The CA's dominant regular domain filter is constructed to locate and classify defects in the domain....

Novel species are introduced into a network of interacting replicators either (i) as mutants of members of the network or (ii) as unrelated immigrants. We consider the meta-population dynamics of such a system. In the first case, the appearance of mutants leads to a slow growth of the replicator...

A simple model of recruitment-based foraging in ants illustrates the idea that synchronized patterns of activity can endow a colony with the ability to forage more efficiently when a minimal number of active individuals is required to establish and maintain food source exploitation. This model,...

The topology of the proteome map revealed by recent large-scale hybridization methods has shown that the distribution of protein-protein interactions is highly heterogeneous, with many proteins having few links while a few of them are heavily connected. This particular topology is shared by...

1. Introduction<p> <p> This essay is written with two goals. The first is to outline the main ideas underlying the growing study of complex economic environments. The second is to suggest areas of public policy where those ideas might be important. Both goals are necessarily speculative. The study of...</p></p>