  Newly formed stars are often observed to possess circumstellar disks, from
which mass continues to be accreted onto the star and fed into outflowing jets,
and which eventually may evolve into dusty debris disks and planetary systems.
Recent modeling developments have made it possible, for the first time, to
study the formation and early evolution of rotationally supported protostellar
disks in the context of a realistic scenario of star formation in weakly
ionized, magnetic, molecular cloud cores. The derived semianalytic solutions
incorporate ambipolar diffusion and magnetic braking and may be extended to
include centrifugally driven disk winds; they can be used to examine the full
range of expected behaviors of real systems and their dependence on physical
parameters.
