Automorphisms and superalgebra structures on the Grassmann algebra

Abstract: Let $F$ be a field of characteristic zero and let $E$ be the Grassmann algebra of an infinite dimensional $F$-vector space $L$. In this paper we study the superalgebra structures (that is the $\mathbb{Z}{2}$-gradings) that the algebra $E$ admits. By using the duality between superalgebras and automorphisms of order $2$ we prove that in many cases the $\mathbb{Z}{2}$-graded polynomial identities for such structures coincide with the $\mathbb{Z}{2}$-graded polynomial identities of the "typical" cases $E{\infty}$, $E_{k^\ast}$ and $E_{k}$ where the vector space $L$ is homogeneous. Recall that these cases were completely described by Di Vincenzo and Da Silva in \cite{disil}. Moreover we exhibit a wide range of non-homogeneous $\mathbb{Z}{2}$-gradings on $E$ that are $\mathbb{Z}{2}$-isomorphic to $E_{\infty}$, $E_{k^\ast}$ and $E_{k}$. In particular we construct a $\mathbb{Z}{2}$-grading on $E$ with only one homogeneous generator in $L$ which is $\mathbb{Z}{2}$-isomorphic to the natural $\mathbb{Z}{2}$-grading on $E$, here denoted by $E{can}$.