Graded Casimir Elements and Central Extensions of Color Lie Algebras
A color Lie algebra is a generalization of a Lie (super)algebra by an Abelian group $Γ$. The underlying vector space and defining relations of the algebra are graded by $Γ$, and a color Lie algebra can admit graded Casimir elements. Furthermore, in that case its loop algebra admits graded central extensions. We present a general method for constructing 2nd order graded Casimir elements and graded central extensions for a given color Lie algebra and its loop algebra, respectively. We also show that there exists a large class of color Lie algebras admitting such graded Casimir elements or central extensions by providing three examples, namely, $\mathfrak{sl}(2)$ for $Γ= \mathbb{Z}_3^2$, and $\mathfrak{q}(n)$ and $\mathfrak{osp}(m|2n)$ for $Γ= \mathbb{Z}_2^2$.