${\mathbb{Z}}_2^3$-grading of the Lie algebra $G_2$ and related color algebras

Abstract

We present a special and attractive basis for the exceptional Lie algebra $G_2$, which turns $G_2$ into a ${\mathbb{Z}}_2^3$-graded Lie algebra. There are two basis elements for each degree of ${\mathbb{Z}}_2^3\setminus \{(0,0,0)\}$, thus yielding 14 basis elements. We give a general and simple closed form expression for commutators between these basis elements. Next, we use this ${\mathbb{Z}}_2^3$-grading in order to examine graded color algebras. Our analysis yields three different ${\mathbb{Z}}_2^3$-graded color algebras of type $G_2$. Since the ${\mathbb{Z}}_2^3$-grading is not compatible with a Cartan-Weyl basis of $G_2$, we also study another grading of $G_2$. This is a ${\mathbb{Z}}_2^2$-grading, compatible with a Cartan-Weyl basis, and for which we can also construct a ${\mathbb{Z}}_2^2$-graded color algebra of type $G_2$.