On Coarse-grained Entropy and Stimulated Emission in Curved Space-Time

We study the entropy generation and particle production in scalar quantum field theory in expanding spacetimes with many-particle mixed initial states. The recently proposed coarse-grained entropy approach by Brandenberger et. al. is applied to systems which may have a non-zero initial entropy. We find that although the the particle production is amplified as a result of boson statistics, the (coarse-grained) entropy generation is {\em attenuated} when initial particles are present.