Generalized Derivations of Lie Algebras

By G. Leger, Eugene M. Luks. 2000

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Abstract Suppose L is a finite-dimensional Lie algebra with multiplication μ: L  ∧  L  →  L . Let Δ( L ) denote the set of triples ( f ,  f ′,  f ″), with f , f ′, f ″ ∈ Hom( L ,  L ), such that μ ∘ ( f  ∧  I L  +  I L  ∧  f ′) =  f ″ ∘ μ. We consider the Lie algebra GenDer( L ) = { f  ∈ Hom( L ,  L )|∃ f ′, f ″: ( f ,  f ′, f ″) ∈ Δ( L )}. Well-researched subalgebras of GenDer( L ) include the derivation algebra, Der( L ) = { f  ∈ Hom( L , L )|( f , f , f ) ∈ Δ( L )}, and the centroid, C( L ) = { f  ∈ Hom( L ,  L )|( f , 0,  f ) ∈ δ( L )}. We now study the subalgebra QDer( L ) = { f  ∈ Hom( L ,  L )|∃ f ′: ( f ,  f ,  f ′) ∈ Δ( L )}, and the subspace QC( L ) = { f  ∈ Hom( L ,  L )|( f , − f , 0) ∈ Δ( L )}. In characteristic ≠ 2, GenDer( L ) = QDer( L ) + QC( L ) and we are concerned with the inclusions Der( L ) ⊆ QDer( L ) and C( L ) ⊆ QC( L ) ∩ QDer( L ). If Z( L ) = 0 then C( L ) = QC( L ) ∩ QDer( L ) and, under reasonable conditions on Lie algebras with toral Cartan subalgebras, we show QDer( L ) = Der( L ) + C( L ); if L is a parabolic subalgebra of a simple Lie algebra of rank > 1 in characteristic 0, then we even have GenDer( L ) = ad( L ) + ( I L ). In general QC( L ) is not closed under composition or Lie bracket; however, if Z( L ) = 0 then QC( L ) is a commutative, associative algebra, and we describe conditions that force QC( L ) = C( L ) or, equivalently, GenDer( L ) = QDer( L ). We show that, in characteristic 0, GenDer( L ) preserves the radical of L , thus generalizing the classical result for Der( L ). We also discuss some applications of the main results to the study of functions f  ∈ Hom( L ,  L ) such that f  ∘ μ or μ ∘ ( f  ∧  I L ) defines a Lie multiplication.

Subfields: Algebra and Number Theory, Discrete Mathematics and Combinatorics, Geometry and Topology

View Paper: https://www.semanticscholar.org/paper/8aaef0e27ba7864fefce97b3f8fe1a6080f342b1

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In Algebra and Number Theory

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  2. Yao Ma
  3. Liangyun Chen
  4. Zhengxin Chen
  5. Dengyin Wang
  6. Yongzheng Zhang
  7. Runxuan Zhang
  8. Xiaoxiang Yu

In Discrete Mathematics and Combinatorics

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In Geometry and Topology

  1. Lin Ni
  2. Yao Ma
  3. Liangyun Chen
  4. Zhengxin Chen
  5. Dengyin Wang
  6. Yongzheng Zhang
  7. Runxuan Zhang
  8. Xiaoxiang Yu

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