Certain aspects of traffic flow measurements imply the existence of a phase transition. Models known from chaos and fractals, such as nonlinear analysis of coupled differential equations, cellular automata, or coupled maps, can generate behavior which indeed resembles a phase transition in the flow behavior. Other measurements point out that the same behavior could be generated by geometrical constraints of the scenario. This paper looks at some of the empirical evidence, but mostly focuses on different modeling approaches. The theory of traffic jam dynamics is reviewed in some detail, starting from the well-established theory of kinematic waves and then veering into the area of phase transitions. One aspect of the theory of phase transitions is that, by changing one single parameter, a system can be moved from displaying a phase transition to not displaying a phase transition. This implies that models for traffic can be tuned so that they display a phase transition or not.This paper focuses on microscopic modeling, i.e., coupled differential equations, cellular automata, and coupled maps. The phase transition behavior of these models, as far as it is known, is discussed. Similarly, fluid-dynamical models for the same questions are considered. A large portion of this paper is given to the discussion of extensions and open questions, which makes clear that the question of traffic jam dynamics is, albeit important, only a small part of an interesting and vibrant field. As our outlook shows, the whole field is moving away from a rather static view of traffic toward a dynamic view, which uses simulation as an important tool.

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In a previous study, we calculated the resolution obtained by a population of overlapping receptive fields, assuming a coarse coding mechanism. The results, which favor large receptive fields, are applied to the visual system of tongue-projecting salamanders. An analytical calculation gives the number of neurons necessary to determine the direction of their prey. Direction localization and distance determination are studied in neural network simulations of the orienting movement and the tongue projection, respectively. In all cases, large receptive fields are found to be essential to yield a high sensory resolution. The results are in good agreement with anatomical, electrophysiological and behavioral data.

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Complexity theory suggests that it is conceivable that there exists a pseudorandom number generator witbin quantum processes. Assuming the existence and knowledge of an appropriate pseudorandom number generator within quantum processes, it is shown that spaceiike transmission of classical bits could emerge theoretically using Einstein-Podolsky-Rosen pairs of particles. Various idealized setups are described.Résumé: La théorie de la complexité suggère qu'il est concevable qu'il existe, dans les processus quantiques, un générateur de nombres pseudo-aléatoires. Postulant l'existence et la connaissance d'un générateur approprié de nombres pseudo-aléatoires, l'article montre que la transmission spacelike d'information classique pourrait émerger théoriquement en utilisant des paires de particules d'Einstein-Podolsky-Rosen. Différentes configurations idéalisées sont décrites.