We address the question "Are some classes of combinatorial optimization problems instrinsically harder than others, without regard to the algorithm one uses, or can difficulty only be assessed relative to particular algorithms?" <p> We provide a measure of the hardness of a particular optimization...</p>

Monte Carlo simulation is widely used to price complex financial instruments. Recent theoretical results and extensive computer testing indicate that deterministic methods may be far superior in speed and confidence. <p> In this paper we test the generalized Faure method due to Tezuka on a...</p>

A detailed analysis of three species-rich ecosystem food webs has shown that they display scale-free distributions of connections. Such graphs of interaction are in fact shared by a number of biological and technological networks, which have been shown to display a very high homeostasis against...

The relation between stable (zero-gradient) points and cellular automata dynamics is explored. Both the number and the nature of stable points influence to some extent the complexity class and stability of rules, and the existence of spatio-temporal structures such as gliders.

RNA molecules interact by forming inter-molecular base pairs that compete with the intra-molecular base pairs of their secondary structures. We investigate the patterns of neutral mutations in RNAs whose function is the interaction with other RNAs, i.e. the co-folding with one or more other RNA...

Template-dependent replication at the molecular level is the basis of reproduction in nature. A detailed understanding of the peculiarities of the chemical reaction kinetics associated with replication processes is therefore an indispensible prerequisite for any understanding of evolution at the...

Our model of shaken sand, presented in earlier work, has been extended to include a more realistic 'glassy' state, i.e. when the sandbox is shaken at very low intensities of vibration. We revisit some of our earlier results, and compare them with our new results on the revised model. Our...

We characterize the distributions of short cycles in a large metabolic network previously shown to have small world characteristics and a power law degree distribution. Compared with three classes of random networks, including Erdős–Rényi random graphs and synthetic small world networks of...