DISSIPATION OF THE STRING EMBEDDING DIMENSION IN THE SINGLET SECTOR OF A MATRIX MODEL AT LARGE ALPHA'

The one-dimensional Fermi gas of matrix eigenvalues of the Marinari-Pa risi model at positive values of the cosmological constant is generali sed. The number of matrix eigenvalues (i.e. ps particles) is varied wh ile keeping the effective potential fixed. This model exhibits a trans ition from a phase whose continuum behaviour is that of c = 1 conforma l matter coupled to gravity to the well-known pure gravity phase of th e original model. The former phase is characterised by an extremely la rge Regge slope alpha' which scales as beta2/5 causing the scaling reg ions of the two phases to overlap. In this way a continuous flow from one phase to the other is made possible. This phase transition occurs in the singlet sector of the matrix model. The density of states and t he two puncture correlator at non-zero momenta are calculated on the s phere and are found to behave very differently in the two phases, a fa ct which demonstrates the phase transition. We comment on a possible r elation between this transition and large alpha' semiclassical expansi ons in the continuum.