Abstract

It is now quite well accepted that during the earliest stages of star formation, protostellar discs can be massive relative to the mass of the central protostar. During this epoch, these discs will be susceptible to the growth of a gravitational instability. In this talk I will discuss semi-analytic calculations and numerical simulations that investigate the formation and evolution of such discs. In particular, I will consider how such discs influence the transport of angular momentum and will consider the likelihood that these discs could fragment to form bound objects. The results suggests that fragmentation is unlikely except at large radii but that these discs are very effective at transporting mass onto the central star and could, during the earliest phases of star formation, be the dominant transport mechanism. I will also discuss the evolution of such discs in the presence of external irradiation which tends to weaken the instability and largely acts to prohibit fragmentation.