Formation of correlations at short time scales and consequences on   interferometry methods
  The formation of correlations due to collisions in an interacting nucleonic system is investigated shortly after a disturbance. Results from one-time kinetic equations are compared with the Kadanoff and Baym two-time equation with collisions included in second order Born approximation. A reasonable agreement is found for a proposed approximation of the memory effects by a finite duration of collisions. The formation of correlations and the build up time is calculated analytically for the high temperature and the low temperature limit. This translates into a time dependent increase of the effective temperature on time scales which interfere with standard fire ball scenarios of heavy ion collisions. The consequences of the formation of correlations on the two- particle interferometry are investigated and it is found that standard extracted lifetimes should be corrected downwards. 
K. Morawetz and H. S. K\"ohler