arXiv subjects
Publications and source records attributed to C. -C. Todea.
We show that for some finite group block algebras, with nontrivial defect groups, the first Hochschild cohomology is nontrivial. Along the way we obtain methods to investigate the nontriviality of the first Hochschild cohomology of some twisted group algebras.
By a result of Gerstenhaber and Schack the simplicial cohomology ring $H^*(\mathcal{C};k)$ of a poset $\mathcal{C}$ is isomorphic to the Hochschild cohomology ring $HH^*(k\mathcal{C})$ of the category algebra $k\mathcal{C}$, where the poset is viewed as a category and $k$ is a field. Extending results of Mishchenko [6], under certain assumptions on a category $\mathcal{C}$, we construct a category $\mathcal{D}$ and a graded $k$-linear isomorphism $HH^*(k\mathcal{C})\cong H^*(\mathcal{D}; k)$. Interpreting the degree one cohomology, we also show how the $k$-space of derivations on $k\mathcal{C}$, graded by some semigroup, corresponds to the $k$-space of characters on $\mathcal{D}$.
BD algebras (Beilinson-Drinfeld algebras) are algebraic structures which are defined similarly to BV algebras (Batalin-Vilkovisky algebras). The equation defining the BD operator has the same structure as the equation for BV algebras, but the BD operator is increasing with degree +1. We obtain methods of constructing BD algebras in the context of group cohomology.