Zuckerman functor

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In mathematics, a Zuckerman functor is used to construct representations of real reductive Lie groups from representations of Levi subgroups. They were introduced by Gregg Zuckerman (1978). The Bernstein functor is closely related.

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[edit] Notation and terminology

  • G is a connected reductive real affine algebraic group (for simplicity; the theory works for more general groups), and g is the Lie algebra of G. K is a maximal compact subgroup of G.
  • L is a Levi subgroup of G, the centralizer of a compact connected abelian subgroup, and *l is the Lie algebra of L.
  • A representation of K is called K-finite if every vector is contained in a finite dimensional representation of K. Denote by WK the subspace of K-finite vectors of a representation W of K.
  • A (g,K)-module is a vector space with compatible actions of g and K, on which the action of K is K-finite.
  • R(g,K) is the Hecke algebra of G of all distributions on G with support in K that are left and right K finite. This is a ring which does not have an identity but has an approximate identity, and the approximately unital R(g,K)- modules are the same as (g,K) modules.

[edit] Definition

The Zuckerman functor Γ is defined by

\Gamma^{g,K}_{g,L\cap K}(W) = \hom_{R(g,L\cap K)}(R(g,K),W)_K

and the Bernstein functor Π is defined by

\Pi^{g,K}_{g,L\cap K}(W) = R(g,K)\otimes_{R(g,L\cap K}W.

[edit] Applications

[edit] References