In mathematics, the Vogel plane is a method of parameterizing simple Lie algebras by eigenvalues ñ, ò, ó of the Casimir operator on the symmetric square of the Lie algebra, which gives a point (ñ: ò: ó) of P<sup>2</sup>/S<sub>3</sub>, the projective plane P<sup>2</sup> divided out by the symmetric group S<sub>3</sub> of permutations of coordinates. It was introduced by , and is related by some observations made by . generalized Vogel's work to higher symmetric powers.
The point of the projective plane (modulo permutations) corresponding to a simple complex Lie algebra is given by three eigenvalues ñ, ò, ó of the Casimir operator acting on spaces A, B, C, where the symmetric square of the Lie algebra (usually) decomposes as a sum of the complex numbers and 3 irreducible spaces A, B, C.