I discuss the relation of Hochschild cohomology to the physical states in the closed topological string. This allows a notion of deformation intrinsic to the derived category. I use this to identify deformations of a quiver gauge theory associated to a D-branes at a singularity with generalized deformations of the geometry of the resolution of the singularity. An explicit map is given from noncommutative deformations (i.e., B-fields) to terms in the superpotential.
"Deformations and D-branes." Adv. Theor. Math. Phys. 12 (4) 781 - 815, August 2008.