  A hom-associative algebra is an algebra whose associativity is twisted by an
algebra homomorphism. In this paper, we define a cup product on the cohomology
of a hom-associative algebra. We show that the cup product together with the
degree $-1$ graded Lie bracket (which controls the deformation of the
hom-associative algebra structure) on the cohomology forms a Gerstenhaber
algebra. This generalizes a classical fact that the Hochschild cohomology of an
associative algebra carries a Gerstenhaber algebra structure.
