  In this talk, we take a new look at the theory of disk locking, which assumes
that an accreting protostar rids itself of accreted angular momentum through a
magnetic coupling with the accretion disk. We consider that differential
rotation between the star and disk twists the field lines. For large enough
twist, the magnetic field lines connecting the star and disk open and
disconnect. This significantly reduces the spin-down torque on the star by the
disk, and so we find that disk-locking theory predicts spin periods that are
much too short to account for typical observed systems.
