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In mathematics, if is a group and is a linear representation of it on the vector space , then the dual representation is defined over the dual vector space as follows:〔Lecture 1 of 〕 : is the transpose of , that is, = for all . The dual representation is also known as the contragredient representation. If is a Lie algebra and is a representation of it on the vector space , then the dual representation is defined over the dual vector space as follows:〔Lecture 8 of 〕 : = for all . In both cases, the dual representation is a representation in the usual sense. ==Motivation== In representation theory, both vectors in and linear functionals in are considered as ''column vectors'' so that the representation can act (by matrix multiplication) from the ''left''. Given a basis for and the dual basis for , the action of a linear functional on , can be expressed by matrix multiplication, :, where the superscript is matrix transpose. Consistency requires :〔Lecture 1, page 4 of 〕 With the definition given, :. For the Lie algebra representation one chooses consistency with a possible group representation. Generally, if is a representation of a Lie group, then given by : is a representation of its Lie algebra. If is dual to , then its corresponding Lie algebra representation is given by :.〔Lecture 8, page 111 of 〕 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「dual representation」の詳細全文を読む スポンサード リンク
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