AU. Note that the massive outer disc forms [*before*]{} the stellar core. This final state is illustrated in Figures \[bate.finalstate\] and \[bate.finalstate2\]. If the calculation was evolved further, the inner circumstellar disc would continue to grow in radius as gas with higher angular momentum fell in. Eventually, the inner disc would meet the outer disc with only a small molecular dissociation region between the two.

Close binary stellar systems
----------------------------

The ability to perform three-dimensional calculations which follow the collapse of molecular cloud cores to stellar densities allows us to study the formation of close ($\simless 1$ AU) binary stellar systems. Currently, there is no accepted mechanism for forming close binaries; the proposal that close binary systems form via the fission of a rapidly-rotating protostellar object has been discredited by studies of rapidly-rotating polytropes [@Durisenetal86]. Although fission itself appears not to operate, it is possible that fragmentation can still occur due to the growth of non-axisymmetric perturbations in rotationally-supported objects. Only two studies have looked at this possibility in detail [@Boss87; @BonBat94b], and the latter of these finds that fragmentation of a massive circumstellar disc on scales ($\simless 1$ AU) may be possible. However, in both these studies, only the 