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c 2006 Old City Publishing, Inc. Published by license under the OCP Science imprint, a member of the Old City Publishing Group
Journal of Cellular Automata, Vol. 2.2, pp. 87–89 Reprints available directly from the publisher Photocopying permitted by license only
Special Issue on Modelling of Complex Systems by Cellular Automata: Guest Editors’ Introduction Jiˇr´ı Kroc1 , Roland Vollmar2 , Moshe Sipper3 and Samira El Yacoubi4 1
Mikkeli Business Campus, Helsinki School of Economics, Finland E-mail:
[email protected] 2 LIIN, University of Karlsruhe, Germany E-mail:
[email protected] 3 Ben-Gurion University, Israel E-mail:
[email protected], 4 University of Perpignan, France E-mail:
[email protected].
The first workshop on Modelling of Complex Systems by Cellular Automata (MCSCA’05) organized under the auspices of the International Conference on Computational Science (ICCS’05) took place in Atlanta in May 2005. Even after more than twenty years of research dedicated to complex systems, there are still a vast number of unclear questions lying at the heart of this field. Answers to old questions always raise even more new questions. New application vistas are continuously opening in all scientific fields ranging from mathematics and physics, across economics and sociology, to biology and medicine. Complex systems provide us an apparently powerful research tool helping to express and simulate many scientific problems in various research fields. The main goal of the MCSCA’05 was to stimulate interdisciplinary collaboration in complex systems and to foster cross-fertilization of diverse scientific fields. Twelve participants present their latest achievements within the scope of the MCSCA’05 workshop in a wide range of fields where all the research is expressed by complex systems using cellular automata as the mathematical framework. Diverse topics—both theoretical and applications— are covered, such as automated design of self-replicating structures using genetic programming methods, models of behaviour of technology markets with network externalities where two firms compete with two different
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technologies, global evolution of general fuzzy cellular automata working with real numbers, epidemiological model with spatially clustered recoveries, abstract painting where a painter and her material acts as a cellular automaton, brood sorting and brood tending behaviour of ants, extremal optimization motivated by self-organized criticality, study of crossing signals in von Neumann 29-state cellular automata, simulation of traffic of cars at a roundabout in a city with advanced rules, study of wealth distribution in a society based on the first degree family relation, a model of virus spread across a society, and simulation of a market behaviour. Six articles representing extended versions of the best works presented at the workshop MCSCA’05 are presented in this issue. In the first paper, Zhijian Pan and James A. Reggia deal with a long standing problem using a novel automated design of self-replicating structures by genetic programming methods. This innovative paper working with a novel approach of automatic search for self-replicating structures and using automaton topology and transition function in form of graph trees found—by application of an evolutionary algorithm which enormously speeds up the search for solution—the biggest self-replicating structures so far evolved. It opens a completely new class of algorithms providing us with computational power that was not so far accessible. In the second paper of Judy Frels, Debra Heisler, James A. Reggia and Hans-Joachim Schuetze, a model behaviour of technology markets with network externalities where two firms compete with two different technologies is studied. Consumers profit from increasing number of other consumers adopting the same product in network markets—where behaviour of consumers depends on behaviour of their close neighbours. For firms, importance of the network to the consumers is critical in selection of correct price penetration strategy of both inferior and superior technology. It is observed that inferior technology may gain substantial market share—of a firm—by price-cutting while it is not probably leading to financial rewards. In his paper, Angelo B. Mingareli studies global evolution of general fuzzy cellular automata using analytical methods—where fuzzy refers to a special procedure that transforms a Boolean cellular automata rule into fuzzy one working with real values. One-dimensional cellular automata represented by rules 30, 110, 18, 45, and 184 (using classical one-dimensional and two valued rule naming procedure) are studied. Long term dynamics of rules is studied and limits are predicted. Cases working with one seed and more seeds in zero background are studied. It is observed that almost all fuzzy rules are not displaying chaotic behaviour. David Hiebeler studies in his work resistance of cellular automata against perturbations of cell neighborhoods in the transition function, which is expressed by a lookup table. A one-dimensional statistic of lookup tables is developed as a measure. The same rule defining a discrete-time cellular
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automaton working with synchronized discrete time steps is transformed into a continuous-time cellular automaton where only one cell per time step is upgraded. It is found that use of a continuous-time cellular automaton using the same lookup table leads to a decrease in complexity of its behaviour compared to its discrete time case. This is related to the loss of synchronicity due to asynchronous updates of neighbouring cells. This show us limits in design of unsynchronized complex machines and obstacles in developing continuous-time spatially extended computing. A study of Tara Krause is an application of complex systems into the field of abstract painting where a painter using her material is motivated by a cellular automaton rule. Different rules could be used to motivate painting. Therefore, cellular automata rules are used indirectly to paint. What is surprising—and not obvious from the first sight—is the fact that the output leads to results having its own beauty. It is shown and widely discussed that a bridge between computer science and painting exists. Finally, the paper of Daniel Merkle, Martin Middendorf and Alexander Scheidler studies brood sorting and brood-tending behaviour of ants—where an ant-colony tends to self-organize itself. The mechanisms of occurrence of patterns of concentric circles around the nest centre are still not fully understood. The model proposed by the authors—where the carbon dioxide distribution inside of the nest and delivery of food to brood are taken into account—is bringing new insights into this fascinating field of research of collective behaviour. We wish to thank the contributing authors and the anonymous referees, without whom this special issue would not have been possible. We are grateful to the Emory University in Atlanta for having provided financial support of the workshop MCSCA’05 and stay of organizers (JK and SY). We especially thank to the organizers of ICCS’05 for the possibility to organize this workshop under their auspices.
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