The Hochschild cohomology ring modulo nilpotence of a stacked monomial algebra
Tom 105 / 2006
Streszczenie
This paper studies the Hochschild cohomology of finite-dimensional monomial algebras. If ${\mit\Lambda} = K{\mathcal Q}/I$ with $I$ an admissible monomial ideal, then we give sufficient conditions for the existence of an embedding of $K[x_1, \ldots , x_r]/\langle x_ax_b \hbox{ for } a \neq b\rangle$ into the Hochschild cohomology ring $\mathop{\rm HH}^*({\mit\Lambda})$. We also introduce stacked algebras, a new class of monomial algebras which includes Koszul and $D$-Koszul monomial algebras. If ${\mit\Lambda}$ is a stacked algebra, we prove that $\mathop{\rm HH}^*({\mit\Lambda})/{\cal N} \cong K[x_1, \ldots , x_r]/\langle x_ax_b \hbox{ for } a \neq b\rangle$, where ${\cal N}$ is the ideal in $\mathop{\rm HH}^*({\mit\Lambda})$ generated by the homogeneous nilpotent elements. In particular, this shows that the Hochschild cohomology ring of ${\mit\Lambda}$ modulo nilpotence is finitely generated as an algebra.
