Baby universes and energy (non-)conservation in (1+1)-dimensional dilaton gravity

Abstract

We consider branching of baby universes off parent one in (1+1)-dimensional dilaton gravity with 24 types of conformal matter fields. This theory is equivalent to string theory in a certain background in D=26-dimensional target space, so this process may be also viewed as the emission of a light string state by a heavy string. We find that bare energy is not conserved in (1+1) dimensions due to the emission of baby universes, and that the probability of this process is finite even for local distribution of matter in the parent universe. We present a scenario suggesting that the non-conservation of bare energy may be consistent with the locality of the baby universe emission process in (1+1) dimensions and the existence of the long ranged dilaton field whose source is bare energy. This scenario involves the generation of longitudinal gravitational waves in the parent universe.