  The space-time light-cone Hamiltonian P^- of large-N matrix models for
dynamical triangulations may be viewed as that of a quantum spin chain and
analysed in a mean field approximation. As N -> infinity, the properties of the
groundstate as a function of the bare worldsheet cosmological constant exhibit
a parton phase and a critical string phase, separated by a transition with
non-trivial scaling at which P- -> -infinity.
