Triggered fragmentation in self-gravitating discs: forming fragments at
  small radii
  We carry out three dimensional radiation hydrodynamical simulations of
gravitationally unstable discs to explore the movement of mass in a disc
following its initial fragmentation. We find that the radial velocity of the
gas in some parts of the disc increases by up to a factor of approximately 10
after the disc fragments, compared to before. While the movement of mass occurs
in both the inward and outward directions, the inwards movement can cause the
inner spirals of a self-gravitating disc to become sufficiently dense such that
they can potentially fragment. This suggests that the dynamical behaviour of
fragmented discs may cause subsequent fragmentation to occur at smaller radii
than initially expected, but only after an initial fragment has formed in the
outer disc.
