Constraint conserving boundary conditions in general relativistic magnetohydrodynamics

Astrophysically, we observe many compact objects, such as neutron stars, which in addition to being examples of strong field gravity, also carry a magnetic field. We are interested in simulating the evolution of such objects using general relativistic magnetohydrodynamics (GRMHD). An important aspect in these models is ensuring that physical constraints are everywhere satisfied during these computations. We describe our efforts to impose consistent boundary conditions to maintain the vanishing of the divergence of the magnetic field.