  The dynamics of dark-bright solitons beyond the mean-field approximation is
investigated. We first examine the case of a single dark-bright soliton and its
oscillations within a parabolic trap. Subsequently, we move to the setting of
collisions, comparing the mean-field approximation to that involving multiple
orbitals in both the dark and the bright component. Fragmentation is present
and significantly affects the dynamics, especially in the case of slower
solitons and in that of lower atom numbers. It is shown that the presence of
fragmentation allows for bipartite entanglement between the distinguishable
species. Most importantly the interplay between fragmentation and entanglement
leads to the splitting of each of the parent mean-field dark-bright solitons,
placed off-center within the parabolic trap, into a fast and a slow daughter
solitary wave. The latter process is in direct contrast to the predictions of
the mean-field approximation. A variety of excitations including dark-bright
solitons in multiple (concurrently populated) orbitals is observed.
Dark-antidark states and domain-wall-bright soliton complexes can also be
observed to arise spontaneously in the beyond mean-field dynamics.
