Example of a morphism between exterior algebras that is $\mathbb{Z}_2$ graded but not $\mathbb{Z}$ graded?? - MathOverflow most recent 30 from http://mathoverflow.net 2013-05-22T01:18:21Z http://mathoverflow.net/feeds/question/81569 http://www.creativecommons.org/licenses/by-nc/2.5/rdf http://mathoverflow.net/questions/81569/example-of-a-morphism-between-exterior-algebras-that-is-mathbbz-2-graded-but Example of a morphism between exterior algebras that is $\mathbb{Z}_2$ graded but not $\mathbb{Z}$ graded?? Oscar Guajardo 2011-11-22T02:48:52Z 2011-11-22T07:25:57Z <p>The title pretty much states my problem. I consider only finitely generated exterior algebras $\bigwedge V$. It is known that any morphism between exterior algebras y determined by its action on generators, i.e. its action on $V$. Does anyone know a good example of this kind of morphisms?</p> <p>By $\mathbb{Z}_2$ graded I mean a morphism of algebras such that the parity of the degree of a form $\eta$ is preserved by such a morphism; and by $\mathbb{Z}$ graded I mean a morphism that preserves the grade of $\eta$, i.e. if $\eta$ is a $k$-form, then so is $f(\eta)$ where $f$ is the morphism in question. Thanks in advance.</p> http://mathoverflow.net/questions/81569/example-of-a-morphism-between-exterior-algebras-that-is-mathbbz-2-graded-but/81587#81587 Answer by S. Carnahan for Example of a morphism between exterior algebras that is $\mathbb{Z}_2$ graded but not $\mathbb{Z}$ graded?? S. Carnahan 2011-11-22T07:25:57Z 2011-11-22T07:25:57Z <p>There doesn't seem to be much more to say, so I'll just repeat Mariano's comment with an example. Let $V$ be a 3-dimensional vector space in degree 1, and consider any nonzero linear map from $V$ to $\wedge^3 V$. This induces an algebra endomorphism of $\bigwedge^\bullet V$ that preserves the $\mathbb{Z}/2\mathbb{Z}$-grading but not the $\mathbb{Z}$-grading.</p>