DefinitionDefinition: Literature-sourcedProof: Not applicablejudge pass (gpt-5.6-terra)audited 2026-09-05
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The Killing form of a semisimple Lie algebra
Definition
Let be a complex semisimple Lie algebra. For , let be the adjoint operators. The Killing form of is the symmetric bilinear form
The trace is taken on the finite-dimensional vector space . This is the invariant form used to define dual bases, the root-theoretic vectors , and the quadratic Casimir element on this page.
Used by
- Smooth and K-finite vectors for SL2(R), and the (g,K)-module Definition
- The quadratic Casimir element Definition
- The Casimir comparison on a weight space Lemma
- The central reduction of U(sl2) is simple away from the finite-dimensional central characters Lemma
- The Chevalley–Eilenberg Laplacian is scalar on weight components Lemma
- The extremal weight cochain of a Weyl element is closed and unique Lemma
- The quadratic Casimir element is independent of the choice of dual bases Lemma
- The Killing form is invariant and nondegenerate on a complex semisimple Lie algebra Proposition
- Under Choice, the Killing form pairs only opposite root spaces Proposition
- Generic irreducibility and the exceptional parameter lattice Theorem
Dependency tree · 0 levels
Nothing. This result depends on no other item in the library.
Sources
- Pavel Etingof, Lie Groups and Lie Algebras I (standard reference, not scraped)