Title: Emergent SU(N) symmetry in disordered SO(N) spin chains,
Abstract: Strongly disordered spin chains invariant under the SO(N) group are shown to
display antiferromagnetic phases with emergent SU(N) symmetry without fine
tuning. The phases with emergent SU(N) symmetry are of two kinds: one has a
ground state formed of randomly distributed singlets of strongly bound pairs of
SO(N) spins (the `mesonic' phase), while the other has a ground state composed
of singlets made out of strongly bound integer multiples of N SO(N) spins (the
`baryonic' phase). Although the mechanism is general, we argue that the cases
N=2,3,4 and 6 can in principle be realized with the usual spin and orbital
degrees of freedom.