  We have studied the interaction between multiple, competing spatial modes
that are excited by a quantum quench of an antiferromagnetic spinor
Bose-Einstein condensate. We observed Hanbury Brown-Twiss correlations and
associated super-Poissonian noise in the mode populations. The decay of these
correlations was consistent with experimentally observed spin domain patterns.
Data were compared with a real-space Bogoliubov theory as well as numerical
solution of the coupled Gross-Pitaevskii equations that were seeded by quantum
noise via the truncated Wigner approximation. The spatial modes that were both
observed experimentally and deduced theoretically are intimately connected to
the inhomogeneous density profile of the condensate, which imparts many rich
features to the dynamics.
