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In mathematics, a Lie bialgebra is the Lie-theoretic case of a bialgebra: it's a set with a Lie algebra and a Lie coalgebra structure which are compatible. It is a bialgebra where the comultiplication is skew-symmetric and satisfies a dual Jacobi identity, so that the dual vector space is a Lie algebra, whereas the comultiplication is a 1-cocycle, so that the multiplication and comultiplication are compatible. The cocycle condition implies that, in practice, one studies only classes of bialgebras that are cohomologous to a Lie bialgebra on a coboundary. They are also called Poisson-Hopf algebras, and are the Lie algebra of a Poisson-Lie group. Lie bialgebras occur naturally in the study of the Yang-Baxter equations. ==Definition== A vector space is a Lie bialgebra if it is a Lie algebra, and there is the structure of Lie algebra also on the dual vector space which is compatible. More precisely the Lie algebra structure on is given by a Lie bracket and the Lie algebra structure on is given by a Lie bracket . Then the map dual to is called the cocommutator, and the compatibility condition is the following cocyle relation: : where is the adjoint. Note that this definition is symmetric and is also a Lie bialgebra, the dual Lie bialgebra. 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「Lie bialgebra」の詳細全文を読む スポンサード リンク
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