Dynamic Density Response of Trapped Interacting Quantum Gases
  An expression for the dynamic density response function has been obtained for an interacting quantum gas in Random Phase Approximation (RPA) including first order self and exchange contribution. It involves the single particle wave functions and eigen values. The expression simplifies when diagonal elements are considered. The diagonal elements of the imaginary part of Fourier transformed response function is relevant in the measurement of Bragg scattering cross-section and in several other applications. 
Renu Bala, J. Bosse, K.N.Pathak
cond-mat.quant-gas