The theory of-modules
In this chapter we study the representation theory of the smallest simple Lie algebra, . The theory as we will develop it goes back to Cartan in the 1890s, but it seems that the results were known to Lie and his student Engel even earlier.
5.1 Classification of irreducibles
Recall from Example 4.1.5 that an-module is a vector space V with three linear transformations eV, hV, ƒV that satisfy the bracket relations