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Concept
Supergroup (physics)
Résumé
The concept of supergroup is a generalization of that of group. In other words, every supergroup carries a natural group structure, but there may be more than one way to structure a given group as a supergroup. A supergroup is like a Lie group in that there is a well defined notion of smooth function defined on them.
However the functions may have even and odd parts. Moreover, a supergroup has a super Lie algebra which plays a role similar to that of a Lie algebra for Lie groups in that they determine most of the representation theory and which is the starting point for classification.
More formally, a Lie supergroup is a supermanifold G together with a multiplication morphism , an inversion morphism and a unit morphism which makes G a group object in the of supermanifolds. This means that, formulated as commutative diagrams, the usual associativity and inversion axioms of a group continue to hold. Since every manifold is a supermanifold, a Lie supergroup generalises the notion of a Lie group.
There are many possible supergroups. The ones of most interest in theoretical physics are the ones which extend the Poincaré group or the conformal group. Of particular interest are the orthosymplectic groups Osp(M|N) and the superunitary groups SU(M|N).
An equivalent algebraic approach starts from the observation that a supermanifold is determined by its ring of supercommutative smooth functions, and that a morphism of supermanifolds corresponds one to one with an algebra homomorphism between their functions in the opposite direction, i.e. that the category of supermanifolds is opposite to the category of algebras of smooth graded commutative functions. Reversing all the arrows in the commutative diagrams that define a Lie supergroup then shows that functions over the supergroup have the structure of a Z2-graded Hopf algebra. Likewise the representations of this Hopf algebra turn out to be Z2-graded comodules. This Hopf algebra gives the global properties of the supergroup.
There is another related Hopf algebra which is the dual of the previous Hopf algebra.
Source officielle
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