Particle Production in Matrix Cosmology
  We consider cosmological particle production in 1+1 dimensional string theory. The process is described most efficiently in terms of anomalies, but we also discuss the explicit mode expansions. In matrix cosmology the usual vacuum ambiguity of quantum fields in time-dependent backgrounds is resolved by the underlying matrix model. This leads to a finite energy density for the "in" state which cancels the effect of anomalous particle production. 
Sumit R. Das, Joshua L. Davis, Finn Larsen and Partha Mukhopadhyay