[過去ログ] 純粋・応用数学・数学隣接分野(含むガロア理論)12 (1002レス)
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(1): 現代数学の系譜 雑談 ◆yH25M02vWFhP 2022/12/31(土)23:57 ID:rNlYJ3SK(32/33) AAS
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他にも非可換群に対する双対理論の類似物は存在していて、いくつかは作用素環論の言葉で定式化されている。基本的な出発点は群 G の群環と双対群 G^ の関数環とが同型になっているということである。

外部リンク:en.wikipedia.org
Pontryagin duality
Dualities for non-commutative topological groups
For non-commutative locally compact groups {\displaystyle G}G the classical Pontryagin construction stops working for various reasons, in particular, because the characters don't always separate the points of {\displaystyle G}G, and the irreducible representations of {\displaystyle G}G are not always one-dimensional. At the same time it is not clear how to introduce multiplication on the set of irreducible unitary representations of {\displaystyle G}G, and it is even not clear whether this set is a good choice for the role of the dual object for {\displaystyle G}G. So the problem of constructing duality in this situation requires complete rethinking.
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233: 現代数学の系譜 雑談 ◆yH25M02vWFhP 2022/12/31(土)23:58 ID:rNlYJ3SK(33/33) AAS
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The theories of first type appeared later and the key example for them was the duality theory for finite groups.[19][20] In this theory the category of finite groups is embedded by the operation {\displaystyle G\mapsto \mathbb {C} _{G}}{\displaystyle G\mapsto \mathbb {C} _{G}} of taking group algebra {\displaystyle \mathbb {C} _{G}}{\displaystyle \mathbb {C} _{G}} (over {\displaystyle \mathbb {C} }\mathbb{C} ) into the category of finite dimensional Hopf algebras, so that the Pontryagin duality functor {\displaystyle G\mapsto {\widehat {G}}}{\displaystyle G\mapsto {\widehat {G}}} turns into the operation {\displaystyle H\mapsto H^{*}}{\displaystyle H\mapsto H^{*}} of taking the dual vector space (which is a duality functor in the category of finite dimensional Hopf algebras).[20]

In 1973 Leonid I. Vainerman, George I. Kac, Michel Enock, and Jean-Marie Schwartz built a general theory of this type for all locally compact groups.[21] From the 1980s the research in this area was resumed after the discovery of quantum groups, to which the constructed theories began to be actively transferred.[22] These theories are formulated in the language of C*-algebras, or Von Neumann algebras, and one of its variants is the recent theory of locally compact quantum groups.[23][22]

One of the drawbacks of these general theories, however, is that in them the objects generalizing the concept of group are not Hopf algebras in the usual algebraic sense.[20] This deficiency can be corrected (for some classes of groups) within the framework of duality theories constructed on the basis of the notion of envelope of topological algebra.[24]
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