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翻訳と辞書　辞書検索 [ 開発暫定版 ] スポンサード リンク Null dust solution ： ウィキペディア英語版 Null dust solution In mathematical physics, a null dust solution (sometimes called a null fluid) is a Lorentzian manifold in which the Einstein tensor is null. Such a spacetime can be interpreted as an exact solution of Einstein's field equation, in which the only mass-energy present in the spacetime is due to some kind of massless radiation. ==Mathematical definition== The Einstein tensor of a null dust must have the form $G^\; =\; 8\; \backslash pi\; \backslash Phi\; \backslash ,\; k^\; \backslash ,\; k^$ where $\backslash vec$ is a null vector field. This definition makes sense in the absence of any physical interpretation, but if we place a stress–energy tensor on our spacetime which happens to have the form $T^\; =\; \backslash Phi\; \backslash ,\; k^\; \backslash ,\; k^$ then Einstein's field equation is trivially satisfied, and in addition, such a stress–energy tensor has a clear physical interpretation in terms of massless radiation. The vector field specifies the direction in which the radiation is moving; the scalar multiplier specifies its intensity. 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「Null dust solution」の詳細全文を読む スポンサード リンク 翻訳と辞書 : 翻訳のためのインターネットリソース Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.