Introduction to the Modeling and Analysis of Complex Systems

Chapter 11Cellular Automata I: Modeling11.1 Definition of Cellular Automata“Automaton” (plural: “automata”) is a technical term used in computer science and mathematicsfor a theoretical machine that changes its internal state based on inputs and itsprevious state. The state set is usually defined as finite and discrete, which often causesnonlinearity in the system’s dynamics.Cellular automata (CA) [18] are a set of such automata arranged along a regular spatialgrid, whose states are simultaneously updated by a uniformly applied state-transitionfunction that refers to the states of their neighbors. Such simultaneous updating is alsocalled synchronous updating (which could be loosened to be asynchronous; to be discussedlater). The original idea of CA was invented in the 1940s and 1950s by Johnvon Neumann and his collaborator Stanisław Ulam. They invented this modeling framework,which was among the very first to model complex systems, in order to describeself-reproductive and evolvable behavior of living systems [11].Because CA are very powerful in describing highly nonlinear spatio-temporal dynamicsin a simple, concise manner, they have been extensively utilized for modeling variousphenomena, such as molecular dynamics, hydrodynamics, physical properties of materials,reaction-diffusion chemical processes, growth and morphogenesis of a living organism,ecological interaction and evolution of populations, propagation of traffic jams, socialand economical dynamics, and so forth. They have also been utilized for computationalapplications such as image processing, random number generation, and cryptography.There are some technical definitions and terminologies you need to know to discussCA models, so here comes a barrage of definitions.Mathematically speaking, CA are defined as a spatially distributed dynamical system185