the collapse of each of the two over-dense regions resulting from the original $m=2$ density perturbation is delayed. The collapse of the larger-scale elongated region, however, continues, leading to the formation of a bar rather than a binary.

It is important to note that, with SPH, the effect of not resolving a Jeans mass also depends on the way the gravitational softening and hydrodynamic smoothing are implemented! If $\epsilon < h$, the ratio of the gravitational to pressure forces between two particles increases with decreasing separation (Figure \[bate.forces\]). This may lead to an instability in which a group of particles within a Jeans-stable clump collapse artificially. As demonstrated in Figure \[bate.10000eh\], this can lead to artificial fragmentation. Alternately, if $\epsilon > h$, the pressure forces between particles within a Jeans-unstable clump may exceed the gravitational forces and the clump will be artificially supported against collapse.

Clearly, the best SPH implementation is one where $\epsilon=h$ always. In this case, collapse of Jeans-unstable clumps with a size similar to that of the resolution length will still be delayed, but the possibilities of artificial collapse within Jeans-stable clumps or the supporting of Jeans-unstable clumps against collapse are eliminated. Then, in order to avoid 