THE YONEDA ALGEBRA OF A K-2 ALGEBRA NEED NOT BE ANOTHER K-2 ALGEBRA

摘要

The Yoneda algebra of a Koszul algebra or a D-Koszul algebra is Koszul. K-2 algebras are a natural generalization of Koszul algebras, and one would hope that the Yoneda algebra of a K-2 algebra would be another K-2 algebra. We show that this is not necessarily the case by constructing a monomial K-2 algebra for which the corresponding Yoneda algebra is not K-2.