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Introduction to the Modeling and Analysis of Complex Systems

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9.1. CHAOS IN DISCRETE-TIME MODELS 1552.5r = 1.82.01.51.00.50.00.50 20 40 60 80 100Figure 9.2: Example <strong>of</strong> <strong>the</strong> “butterfly effect,” <strong>the</strong> extreme sensitivity <strong>of</strong> chaotic systems<strong>to</strong> initial conditions. The two curves show time series generated using Eq. (8.37) withr = 1.8; one with x 0 = 0.1 <strong>and</strong> <strong>the</strong> o<strong>the</strong>r with x 0 = 0.100001.Exercise 9.1 There are many simple ma<strong>the</strong>matical models that exhibit chaoticbehavior. Try simulating each <strong>of</strong> <strong>the</strong> following dynamical systems (shown inFig. 9.3). If needed, explore <strong>and</strong> find <strong>the</strong> parameter values with which <strong>the</strong> systemshows chaotic behaviors.• Logistic map: x t = rx t−1 (1 − x t−1 )• Cubic map: x t = x 3 t−1 − rx t−1• Sinusoid map: x t = r sin x t−1• Saw map: x t = fractional part <strong>of</strong> 2x t−1Note: The saw map may not show chaos if simulated on a computer, but it will showchaos if it is manually simulated on a cobweb plot. This issue will be discussedlater.predictions for our future!

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