Zoom-Simulations of Protoplanetary Disks starting from GMC scales
  We investigate the formation of protoplanetary disks around nine solar mass
stars formed in the context of a (40 pc)$^3$ Giant Molecular Cloud model, using
RAMSES adaptive-mesh refinement simulations extending over a scale range of
about 4 million, from an outer scale of 40 pc down to cell sizes of 2 AU. Our
most important result is that the accretion process is heterogeneous in
multiple ways; in time, in space, and among protostars of otherwise similar
mass. Accretion is heterogeneous in time, in the sense that accretion rates
vary during the evolution, with generally decreasing profiles, whose slopes
vary over a wide range, and where accretion can increase again if a protostar
enters a region with increased density and low speed. Accretion is
heterogeneous in space, because of the mass distribution, with mass approaching
the accreting star-disk system in filaments and sheets. Finally, accretion is
heterogeneous among stars, since the detailed conditions and dynamics in the
neighborhood of each star can vary widely. We also investigate the sensitivity
of disk formation to physical conditions, and test their robustness by varying
numerical parameters. We find that disk formation is robust even when choosing
the least favorable sink particle parameters, and that turbulence cascading
from larger scales is a decisive factor in disk formation. We also investigate
the transport of angular momentum, finding that the net inward mechanical
transport is compensated for mainly by an outward directed magnetic transport,
with a contribution from gravitational torques usually subordinate to the
magnetic transport.
