Dielectric formalism and damping of collective modes in trapped   Bose-Einstein condensed gases
  We present the general dielectric formalism for Bose-Einstein condensed systems in external potential at finite temperatures. On the basis of a model arising within this framework as a first approximation in an intermediate temperature region for large condensate we calculate the damping of low-energy excitations in the collisionless regime. 
Gy. Bene and P. Szepfalusy (Eotvos University, Budapest)