GRACEFUL EXIT PROBLEM AND STRESS-ENERGY-MOMENTUM TENSORS REVISITED INTHE 2-DIMENSIONAL STRING COSMOLOGY

We study the graceful exit problem and the role of the stress-energy-m omentum tensors in the two-dimensional string cosmology. The one-loop quantum correction of conformal fields is incorporated in the arbitrar y large N limit to ensure exact quantum solvability. The only solution which gives the bounded curvature with the asymptotic flatness is res tricted to the first branch under some conditions. However, even in th is case, the accelerating expansion is forever. We show that the only nonvanishing quantum stress-momentum tensor is the pressure part (T-xx ) which is of relevance to the dynamical evolution of the universe in the comoving coordinate. The quantum energy part is zero since the neg ative contribution of the induced conformal matters always cancels the positive quantity of the induced dilaton part in terms of the constra int equations. (C) 1998 Published by Elsevier Science B.V.