  We report diffusion Monte Carlo results for the ground state of unpolarized
spin-1/2 fermions in a cylindrical container and properties of the system with
a vortex-line excitation. The density profile of the system with a vortex line
presents a non-zero density at the core. We calculate the ground-state energy
per particle, the superfluid pairing gap, and the excitation energy per
particle. These simulations can be extended to calculate the properties of
vortex excitations in other strongly interacting systems, such as superfluid
neutron matter using realistic nuclear Hamiltonians.
