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In mathematics, Stone's theorem on one-parameter unitary groups is a basic theorem of functional analysis that establishes a one-to-one correspondence between self-adjoint operators on a Hilbert space and one-parameter families : Such one-parameter families are ordinarily referred to as strongly continuous one-parameter unitary groups. The theorem was proved by , and showed that the requirement that be strongly continuous can be relaxed to say that it is merely weakly measurable, at least when the Hilbert space is separable. This is a very stunning theorem, as it allows to define the derivative of the mapping , which is only supposed to be continuous. It is also related to the theory of Lie groups and Lie algebras. == Formal statement == Let Conversely, let be a (not necessarily bounded) self-adjoint operator on a Hilbert space . Then the one-parameter family is a strongly continuous one-parameter group. The infinitesimal generator of :and then extending to all of by continuity. * Use the Fourier transform to obtain a non-degenerate *-representation of on . * By the Riesz-Markov Theorem, gives rise to a projection-valued measure on that is the resolution of the identity of a unique self-adjoint operator , which may be unbounded. * Then is the infinitesimal generator of . Then is defined to be the enveloping C *-algebra of , i.e., its completion with respect to the largest possible C *-norm. It is a non-trivial fact that, via the Fourier transform, is isomorphic to . A result in this direction is the Riemann-Lebesgue Lemma, which says that the Fourier transform maps to . 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「Stone's theorem on one-parameter unitary groups」の詳細全文を読む スポンサード リンク
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