  When they first appear in the HR diagram, young stars rotate at a mere 10\%
of their break-up velocity. They must have lost most of the angular momentum
initially contained in the parental cloud, the so-called angular momentum
problem. We investigate here a new mechanism by which large amounts of angular
momentum might be shed from young stellar systems, thus yielding slowly
rotating young stars. Assuming that planets promptly form in circumstellar
disks and rapidly migrate close to the central star, we investigate how the
tidal and magnetic interactions between the protostar, its close-in planet(s),
and the inner circumstellar disk can efficiently remove angular momentum from
the central object. We find that neither the tidal torque nor the variety of
magnetic torques acting between the star and the embedded planet are able to
counteract the spin up torques due to accretion and contraction. Indeed, the
former are orders of magnitude weaker than the latter beyond the corotation
radius and are thus unable to prevent the young star from spinning up. We
conclude that star-planet interaction in the early phases of stellar evolution
does not appear as a viable alternative to magnetic star-disk coupling to
understand the origin of the low angular momentum content of young stars.
