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In the mathematical field of dynamical systems, a random dynamical system is a dynamical system in which the equations of motion have an element of randomness to them. Random dynamical systems are characterized by a state space ''S'', a set of maps ''T'' from ''S'' into itself that can be thought of as the set of all possible equations of motion, and a probability distribution ''Q'' on the set ''T'' that represents the random choice of map. Motion in a random dynamical system can be informally thought of as a state evolving according to a succession of maps randomly chosen according to the distribution ''Q''. An example of a random dynamical system is a stochastic differential equation; in this case the distribution Q is typically determined by ''noise terms''. It consists of a base flow, the "noise", and a cocycle dynamical system on the "physical" phase space. ==Motivation: solutions to a stochastic differential equation== Let be a -dimensional vector field, and let . Suppose that the solution to the stochastic differential equation : exists for all positive time and some (small) interval of negative time dependent upon , where denotes a -dimensional Wiener process (Brownian motion). Implicitly, this statement uses the classical Wiener probability space : In this context, the Wiener process is the coordinate process. Now define a flow map or (solution operator) by : (whenever the right hand side is well-defined). Then (or, more precisely, the pair ) is a (local, left-sided) random dynamical system. The process of generating a "flow" from the solution to a stochastic differential equation leads us to study suitably defined "flows" on their own. These "flows" are random dynamical systems. 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Random dynamical system」の詳細全文を読む スポンサード リンク
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