English
The Lie algebra associated to a Cartan matrix is defined as the free Lie algebra modulo the Cartan relations.
Русский
Ли-алгебра, ассоциированная с Картановой матрицей, определена как свободная Ли-алгебра по модулю реляций Картанa.
LaTeX
$$$\\text{ToLieAlgebra} := \\operatorname{FreeLieAlgebra}(R,[Generators]) / \\text{CartanMatrix.Relations.toIdeal } R A$$$
Lean4
/-- The Lie algebra corresponding to a Cartan matrix.
Note that it is defined for any matrix of integers. Its value for non-Cartan matrices should be
regarded as junk. -/
def ToLieAlgebra :=
FreeLieAlgebra R _ ⧸ CartanMatrix.Relations.toIdeal R A
deriving LieRing, Inhabited, LieAlgebra R