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In mathematics, the Kolmogorov extension theorem (also known as Kolmogorov existence theorem or Kolmogorov consistency theorem) is a theorem that guarantees that a suitably "consistent" collection of finite-dimensional distributions will define a stochastic process. It is credited to the Soviet mathematician Andrey Nikolaevich Kolmogorov. ==Statement of the theorem== Let denote some interval (thought of as "time"), and let . For each and finite sequence of times , let be a probability measure on . Suppose that these measures satisfy two consistency conditions: 1. for all permutations of and measurable sets , : 2. for all measurable sets , : Then there exists a probability space and a stochastic process such that : for all , and measurable sets , i.e. has as its finite-dimensional distributions relative to times . In fact, it is always possible to take as the underlying probability space and to take for the canonical process . Therefore, an alternative way of stating Kolomogorov's extension theorem is that, provided that the above consistency conditions hold, there exists a (unique) measure on with marginals for any finite collection of times . Kolmogorov's extension theorem applies when is uncountable, but the price to pay for this level of generality is that the measure is only defined on the product σ-algebra of , which is not very rich. 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「Kolmogorov extension theorem」の詳細全文を読む スポンサード リンク
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