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In mathematics, Cartan's criterion gives conditions for a Lie algebra in characteristic 0 to be solvable, which implies a related criterion for the Lie algebra to be semisimple. It is based on the notion of the Killing form, a symmetric bilinear form on defined by the formula : where tr denotes the trace of a linear operator. The criterion was introduced by .〔Cartan, Chapitre IV, Théorème 1〕 == Cartan's criterion for solvability == Cartan's criterion for solvability states: :''A Lie subalgebra of endomorphisms of a finite-dimensional vector space over a field of characteristic zero is solvable if and only if whenever '' The fact that in the solvable case follows immediately from Lie's theorem that solvable Lie algebras in characteristic 0 can be put in upper triangular form. Applying Cartan's criterion to the adjoint representation gives: :''A finite-dimensional Lie algebra over a field of characteristic zero is solvable if and only if (where K is the Killing form).'' 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「Cartan's criterion」の詳細全文を読む スポンサード リンク
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