  Previous simulations of self-gravitating protostellar disks have shown that,
once developed, gravitational instabilities are enhanced by cooling the disk
constantly during its evolution (Pickett et al. 2002). These earlier
calculations included a very simple form of volumetric cooling, with a constant
cooling time throughout the disk, which acted against the stabilizing effects
of shock heating. The present work incorporates more realistic treatments of
energy transport. The initial disk model extends from 2.3 to 40 AU, has a mass
of 0.07 Msun and orbits a 0.5 Msun star. The models evolve for a period of over
2500 years, during which extensive spiral arms form. The disks structure is
profoundly altered, transient clumps form in one case, but no permanent bound
companion objects develop.
