Hochschild cohomology of Jacobian algebras from unpunctured surfaces: A geometric computation

Abstract: There are several examples in which algebraic properties of Jacobian algebras from (unpunctured) Riemann surfaces can be computed from the geometry of the Riemann surface. In this work, we compute the dimension of the Hochschild cohomology groups of any Jacobian algebra from unpunctured Riemann surfaces. In those expressions appear geometric objects of the triangulated surface, namely: the number of internal triangles and certain types of boundaries. Moreover, we give geometric conditions on the triangulated surface $(S,M,\mathbb T)$ such that the Gerstenhaber algebra $\operatorname{HH}^*(A_{\mathbb T})$ has non-trivial multiplicative structures. We also show that the derived class of Jacobian algebras from an unpunctured surface $(S,M)$ is not always completely determined by the Hochschild cohomology.