4-DIMENSIONAL COSMOLOGY FROM DILATON COUPLED QUANTUM MATTER IN 2 DIMENSIONS

The reduction of 4D Einstein gravity with N minimal scalars leads to s pecific 2D dilaton gravity with dilaton coupled scalars. Applying s-wa ve and large N approximation (where large N quantum contribution due t o dilaton itself is taken into account) we study 2D cosmology for CGHS model and for reduced Einstein gravity tin both cases with dilaton co upled scalers). Numerical study shows that in most cases we get 2D sin gular Universe which may correspond to big bang. Nevertheless, big cru nch or non-singular Universes are also possible. For reduced 4D Einste in gravity one can regard the obtained 2D cosmology with time-dependen t dilaton as 4D Kantowski-Sacks Universe of singular, non-singular or big crunch type. (C) 1998 Published by Elsevier Science B.V. All right s reserved.