Semidirect product Adjoining a derivation Let be a Lie algebra over and be a derivation on . Then one may adjoin the derivation to by taking the semidirect product lie where is the free vector space generated by with the unique (abelian) bracket.1 Special cases Adjoining the degree derivation develop | en | sembr Footnotes 1988. Vertex operator algebras and the Monster, §1.3, p. 8 ↩